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The modular nature of protein evolution: domain rearrangement rates across eukaryotic life

  • Westphalia University of Applied Sciences, Gelsenkirchen, Bocholt, Recklinghausen

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Background: Modularity is important for evolutionary innovation. The recombination of existing units to form larger complexes with new functionalities spares the need to create novel elements from scratch. In proteins, this principle can be observed at the level of protein domains, functional subunits which are regularly rearranged to acquire new functions. Results: In this study we analyse the mechanisms leading to new domain arrangements in five major eukaryotic clades (vertebrates, insects, fungi, monocots and eudicots) at unprecedented depth and breadth. This allows, for the first time, to directly compare rates of rearrangements between different clades and identify both lineage specific and general patterns of evolution in the context of domain rearrangements. We analyse arrangement changes along phylogenetic trees by reconstructing ancestral domain content in combination with feasible single step events, such as fusion or fission. Using this approach we explain up to 70% of all rearrangements by tracing them back to their precursors. We find that rates in general and the ratio between these rates for a given clade in particular, are highly consistent across all clades. In agreement with previous studies, fusions are the most frequent event leading to new domain arrangements. A lineage specific pattern in fungi reveals exceptionally high loss rates compared to other clades, supporting recent studies highlighting the importance of loss for evolutionary innovation. Furthermore, our methodology allows us to link domain emergences at specific nodes in the phylogenetic tree to important functional developments, such as the origin of hair in mammals. Conclusions: Our results demonstrate that domain rearrangements are based on a canonical set of mutational events with rates which lie within a relatively narrow and consistent range. In addition, gained knowledge about these rates provides a basis for advanced domain-based methodologies for phylogenetics and homology analysis which complement current sequence-based methods.
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Dohmen et al. BMC Evolutionary Biology (2020) 20:30
The modular nature of protein
evolution: domain rearrangement rates
across eukaryotic life
Elias Dohmen1,2 , Steffen Klasberg1†, Erich Bornberg-Bauer1, Sören Perrey2and Carsten Kemena1*
Background: Modularity is important for evolutionary innovation. The recombination of existing units to form larger
complexes with new functionalities spares the need to create novel elements from scratch. In proteins, this principle
can be observed at the level of protein domains, functional subunits which are regularly rearranged to acquire new
Results: In this study we analyse the mechanisms leading to new domain arrangements in five major eukaryotic
clades (vertebrates, insects, fungi, monocots and eudicots) at unprecedented depth and breadth. This allows, for the
first time, to directly compare rates of rearrangements between different clades and identify both lineage specific and
general patterns of evolution in the context of domain rearrangements. We analyse arrangement changes along
phylogenetic trees by reconstructing ancestral domain content in combination with feasible single step events, such
as fusion or fission. Using this approach we explain up to 70% of all rearrangements by tracing them back to their
precursors. We find that rates in general and the ratio between these rates for a given clade in particular, are highly
consistent across all clades. In agreement with previous studies, fusions are the most frequent event leading to new
domain arrangements. A lineage specific pattern in fungi reveals exceptionally high loss rates compared to other
clades, supporting recent studies highlighting the importance of loss for evolutionary innovation. Furthermore, our
methodology allows us to link domain emergences at specific nodes in the phylogenetic tree to important functional
developments, such as the origin of hair in mammals.
Conclusions: Our results demonstrate that domain rearrangements are based on a canonical set of mutational
events with rates which lie within a relatively narrow and consistent range. In addition, gained knowledge about these
rates provides a basis for advanced domain-based methodologies for phylogenetics and homology analysis which
complement current sequence-based methods.
Keywords: Protein domain, Rearrangement rates, Proteome analysis, Evolutionary history, Ancestral reconstruction
Functional adaptations of proteins have often been
observed to be caused by point mutations changing amino
acids at crucial positions. These mutations typically result
in altered specificity or stability of a protein. Although this
process is important for evolutionary adaptations, point
mutations often result in only minor changes of a protein.
Elias Dohmen and Steffen Klasberg contributed equally to this work.
1Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasse 1,
48149 Münster, Germany
Full list of author information is available at the end of the article
For greater functional changes or innovation, more drastic
modifications are necessary that do not rely on numerous
Molecular mechanisms like crossing over, alternative
splicing and transposition through mobile elements can
cause mutational events that rearrange larger DNA frag-
ments and therefore also alter larger regions at the protein
level. Examples of such mutational events, which rear-
range gene content, are for example fusion and fission.
All these events lead to rearrangements that can be eas-
ily tracked at the level of protein domains, since domains
are well characterised in many databases (e.g. in the Pfam
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Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 2 of 13
[1]orSuperfamily [2] database) and represent reusable
structural and functional units.
The total number of defined domains is relatively small
and is growing only slowly. For example, the Pfam domain
database [1] defines about 18,000 domains in its current
version (version 32). On the other hand, the number of
known unique domain arrangements - defined by the lin-
ear order of domains in an amino acid sequence [3]-is
much larger and growing rapidly [4]. Accordingly, rear-
rangements of existing domains can help explain the vast
protein diversity we observe in nature [49].
Several studies have shown that domain rearrangements
are essential in the evolution of pathways, signalling net-
works and cellular components. The evolution of the
extracellular matrix in metazoans [10]aswellastheblood
coagulation cascade [11] are examples in which the reuse
of domains in different contexts are considered crucial
steps. Additionally, domains have been identified to play
an important role in signalling networks [12] or their
recombination to new arrangements in T-Cell develop-
ment [13]. Lees et al. [14] showed the importance of
domain arrangement changes in cancer genome evolu-
tion. Therefore, it is crucial to analyse domain changes
when studying both genome evolution and specific pro-
tein families.
First attempts to study general evolutionary domain
patterns focused mainly on emergence and loss of sin-
gle domains [15,16] or domain repeats [17,18]. Later,
quantitative analyses in plants and insects [19,20]over
time-scales of several hundred million years revealed hot-
spots of rearrangement events at specific nodes in the
phylogenetic tree. Both these studies took into account
four different types of rearrangement events: fusion, fis-
sion, terminal addition and terminal loss. Together, these
events are sufficient to explain a large proportion (60%-
70%) of the new domain arrangements considered in those
Based on these four single step events, rearrangement
rates for a set of 29 plant species (dating back as far as 800
my [19]) and 20 Pancrustacean species (dating back 430
my [20]) were determined in previous studies.
In this study we use expanded species sets (up to 72
species per phylogenetic clade) to detect common pat-
terns of domain evolution and consider several thousand
more arrangements per clade compared to the two previ-
ously mentioned studies. In total, domain arrangements in
five different eukaryotic clades (vertebrates, insects, fungi,
monocots and eudicots) are analysed. For the first time,
the results can be directly compared between these clades,
since exactly the same methodology was applied to all of
Previously, methods were applied that had used either
overlapping definitions for rearrangement events, or that
analysed domain loss and emergence (e.g. [16]) separately
from rearrangement events (e.g. [20]). In this study, we
combine these methodologies in one consistent model,
allowing us to distinguish six different single step events,
thereby analysing the molecular mechanisms leading to
protein innovation at unprecedented accuracy. The incor-
poration of additional clades and a higher number of
species ensures the integrity of the observed events, for
example by minimising annotation biases. The resulting
rearrangement frequencies are directly comparable across
the different eukaryotic clades and thus reveal the fun-
damental mechanisms of functional rearrangements in
eukaryotes, in addition to lineage specific trends.
Furthermore, we infer functional implications of the
new arrangements via Gene Ontology (GO) [21]term
enrichment. Finally, we discuss how our methodology can
be used to complement existing methods for example
in phylogenetic reconstruction, by incorporating data on
domain rearrangements.
To be able to draw reliable conclusions about universally
valid mechanisms in protein evolution, it is necessary to
ensure that a sufficient number of observable rearrange-
ments can be explained by the six different rearrangement
events defined in this manuscript (fusion,fission,termi-
nal loss/emergence and single domain loss/emergence;see
Methods). For this purpose we reconstructed the ances-
tral domain content and arrangements at all inner nodes
of the phylogenetic trees of five eukaryotic clades (ver-
domain arrangements that differ from the parental node,
we examined whether the change could be explained
uniquely by one of the six events.
Unique solutions are either exact solutions,whereonlya
single event can explain the arrangement change, or non-
ambiguous solutions, where multiple events of the same
type can explain a new arrangement (e.g. ABC: A+BC /
AB+C). Only unique solutions were further analysed in
detail to focus on changes which can be explained with
certainty (Additional file 2). Unique solutions can explain
50% to 70% of all observed new arrangements, depending
on the analysed phylogenetic clade (Fig. 1).
However, there is a small percentage of new arrange-
ments which can be explained by multiple different event
types, i.e. ambiguous solutions (e.g. ABC: ABC-D / AB+C).
Beside these ambiguous solutions, some new arrange-
ments cannot be explained by the defined single step
events. These so-called complex solutions (25%-50%),
would require several successive single step events.
Comparison between clades
One major goal of this study is to find, beside clade-
specific differences, universally valid evolutionary mech-
anisms of protein innovation that are present in all
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 3 of 13
Fig. 1 Frequency of the different solution types. Exact and non-ambiguous solutions can be found in about 50% of the cases
clades. Therefore, we analyse whether common patterns
in domain rearrangements can be observed by measur-
ing the relative contributions of each rearrangement event
and compare them between the different clades (see
Table 1and Additional file 4).
from 29% in fungi to 64% of all observed events in
monocots. Only in fungi, fusions represent not the most
frequent event type, but single domain loss is most fre-
quent. Furthermore, in all clades except fungi, fissions
and terminal losses account for a similar percentage of
all domain rearrangements. In fungi, loss of terminal
domains accounts for twice as many rearrangements as
fissions. The exceptional distribution of event frequencies
in fungi compared to the other clades is discussed below.
The very low contributions of the two emergence cat-
egories, terminal and single domain emergence, of only
0.13% to 3.89% show that domain emergence is indeed
rare compared to a much higher number of domain rear-
rangements and losses.
We observed three general patterns of the ranks of
rearrangement events corresponding to the taxonomic
kingdoms of animals, fungi, and plants. In the first pattern,
observed in animals (i.e. vertebrates and insects), the most
frequent domain rearrangement event is domain fusion
(32% and 42% of rearrangements respectively), followed
Table 1 Frequencies of the six rearrangement events (in %)
Vertebrates Insects Fungi Monocots Eudicots
Fusion 32.45 41.52 29.35 64.43 58.22
Fission 19.57 17.21 8.80 12.21 16.28
Terminal loss 20.52 19.21 16.46 10.59 13.00
Terminal emergence 0.13 0.36 0.76 1.01 0.48
Single loss 26.71 19.99 40.74 9.83 10.20
Single emergence 0.61 1.71 3.89 1.93 1.82
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 4 of 13
by single domain loss (27% and 20%) and terminal domain
loss (21% and 19%). Arrangement gain by fission is slightly
less common (20% and 17%), but still more frequent than
the very low rates of single domain emergence (0.6% and
1.7%) and terminal emergence (0.1% and 0.4%).
The functional analysis of gained arrangements in
insects (Additional file 5) using GO term enrichment
reveals olfaction related adaptations (represented by GO
terms of ’sensory perception of smell’, ’olfactory recep-
tor activity’ and ’odorant binding’) are overrepresented in
insects. Other overrepresented GO terms include ’sensory
perception of taste’ and ’structural constituent of cuticle’.
We did not find expansions of vertebrate specific GO
terms at the root of vertebrates. However, we found over-
represented GO terms related to binding (e.g. ’protein
binding’, ’nucleic acid binding’) and terms related to signal
transduction (Additional file 6).
The distribution and rank of rearrangement rates in
Fungi (Additional file 7) resemble those of animals, with
the only qualitative difference being that single domain
losses were more frequent than fusions. A more detailed
analysis of this phenomenon can be found below.
The third pattern of arrangement changes is observed
in plants, i.e. monocots and eudicots. As in meta-
zoans, but with an even higher percentage, the major-
ity of new arrangements is explained by fusion (64%
and 58%). The fission of one arrangement into two new
arrangements is the second most frequent mechanism
(12% and 16%) followed by slightly smaller numbers of
terminal (11% and 13%) and single domain loss (10% and
Some GO terms are enriched in gained arrangements at
the root of both plant clades that might be related to plant
development and evolution, i.e. ’recognition of pollen’ in
both plant clades or ’plant-type cell wall organization’ in
eudicots (Fig. 2and Additional file 8).
Domain loss in fungi
We analysed the distribution of domain arrangement sizes
in the five clades (see Additional file 9) to find possible
explanations for the different patterns of event frequen-
cies mentioned above. The results show that a strikingly
high number of fungal domain arrangements consists of
just a single domain and their arrangements are gener-
ally much shorter compared to vertebrates or insects.
Both plant clades, monocots and eudicots, also have much
shorter domain arrangements than the metazoan clades.
We found that both plant clades show the highest
copy number of domain arrangements. Eudicots have 5.79
copies on average per single domain arrangement per
species, while monocots have 5.64. This high number
of duplications of the same domain arrangement could
be explained by multiple whole genome duplications in
these clades. Vertebrates follow with 1.93 copies per single
domain arrangement and finally insects (1.27), while fungi
show the lowest duplication count (1.15).
Fig. 2 Number of rearrangement events across the eudicot phylogeny. Digit representation of the total number of rearrangement events at a
specific node is indicated next to the pie chart. For details on ’Outgroups’ see Methods. Significant GO terms in gained domain arrangements are
shown in a tag cloud (box). GO terms that might point to eudicot specific evolution are: ’recognition of pollen’ and ’plant-type cell wall organization’
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 5 of 13
Effects of domain rearrangements
The general rates of rearrangement events and their dis-
tribution in a given phylogenetic tree can provide an
insight into the evolutionary history of a whole clade as
well as general adaptational processes in certain lineages.
However, by taking a more detailed look at the specific
domains involved in the rearrangement events at specific
time points, we can trace back some major steps in the
evolutionary history of the studied species. Here, we show
three examples of new or outstanding functions at specific
nodes in the evolution of vertebrates, plants and insects
which can be related to the emergence of new domains or
domain arrangements.
The origin of hair and adaptations of the immune system in
One remarkable pattern in the distribution of rearrange-
ment events in the vertebrate phylogeny is the high rate
(33%) of single domain emergences at the root of all mam-
mals. This represents the highest percentage of single
domain emergences at any node in the vertebrate tree.
A closer investigation of the function of these emerged
domains shows that 30% of the emerged domains
(domains of unknown function excluded) are associated
with hair. This finding is a strong signal for the origin of
hair or fur, respectively, in the common ancestor of all
One of the most important structural protein fami-
lies of mammalian hair is the keratin-associated pro-
tein family (KRTAPs). Hair keratins are embedded in an
inter-filamentous matrix consisting of KRTAPs located
in the hair cortex. Two major types of KRTAPs can
be distinguished: high-sulfur/ultra-high-sulfur and high-
glycine/tyrosine KRTAPs [22]. Three of these high-sulfur
proteins can be found in the set of emerged domains
as ’Keratin, high sulfur B2 protein’ (Pfam-ID: PF01500),
’Keratin-associated matrix’ (PF11759) and ’Keratin, high-
sulphur matrix protein’ (PF04579). The proteins are syn-
thesised during the hair matrix cell differentiation and
form hair fibres in association with hair keratin inter-
mediate filaments. Another domain that can be found in
this set is the ’PMG protein’ (PF05287) domain, which
occurs in two genes in mice (PMG1 and PMG2) that
are known to be expressed in growing hair follicles and
are members of a KRTAP gene family [23]. PMG1 and
PMG2 are additionally involved in epithelial cell differen-
tiation, while a further member of the emerged domains
- ’KRTDAP’ (PF15200) - is a keratinocyte differentiation-
associated protein. Keratinocytes are a cell type of the
epidermis, the layer of the skin closest to the surface [24].
The KRTDAP related gene was isolated in rats between
skin of prehair-germ stage embryos and hair-germ stage
embryos, and shows high expression in regions of the
hair follicle [25]. We can infer that the emergence of hair
and fur also involved adaptation and restructuring of the
skin, resulting in novel skin cell types and cell differenti-
ation regulation mechanisms. Furthermore, the skin, and
keratinocytes in particular, act as a first barrier against
environmental damage and pathogen infestation and are
therefore related to the second barrier, the immune sys-
tem. Indeed, immune system related domains are the
second biggest group in these emerged domains (>20%
of domains with known function). As an example, the
’Interleukin’ domain (PF03487) emerged at the root of
teins and signalling molecules. The mammalian immune
system is highly dependent on interleukins with certain
deficiencies linked to autoimmune diseases and other
immune system defects [26]. ’Lymphocyte activation fam-
ily X’ is a domain also found in this set (PF15681),
which is membrane-associated and expressed in B- and
T-cells in addition to other lymphoid-specific cell types
[27]. Additionally, out of all events occurring at the root
of mammals, ’regulation of lymphocyte activation’ is an
overrepresented term in the GO term enrichment anal-
ysis (see Additional file 10). These results reinforce the
importance of the immune system for the early evolution
of mammals.
Resistance to fungi in wheat
The functional analysis of gained domain arrangements
using GO terms revealed an interesting pattern for the
node leading to Triticeae which includes the two wheat
species Triticum urartu and Triticum aestivum as well
as the grass species Aegilops tauschii.Fiveoutofthe
15 enriched GO terms in Triticeae can be related to
resistance to fungal pathogens via three different mech-
anisms. Chitinases are enzymes, which are known to be
involved in plants’ fungal resistance and have been exten-
sively studied in wheat species [28,29]. The ability of
these enzymes to degrade chitin, a primary component
of fungal cell walls, can lead to the lysis of fungal cells
and therefore provide resistance against them. We found
the three significant GO terms ’chitin catabolic process’,
’cell wall macromolecular catabolic process’ and ’protein
phosphorylation’ related to chitinases, which explain the
innate fungal resistance of wheat and can also be uti-
lized in genetic engineering to enhance fungal resistance
in other crop plants [30]. The GO term ’protein kinase
activity’ and the underlying Serine Threonine kinase
has also been shown to be used in plants’ defense to
fungi [31]. Another mechanism of fungal resistance is
based on an ATP-binding cassette transporter, which is
used in many crop plants [32]. We relate the GO term
of ’ATP binding’ to this function of fungal resistance.
Overall, the gained arrangements in Triticeae can be
linked to the increased resistance of this clade to fungal
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 6 of 13
Eusociality in bees
We found an example of interesting GO terms enriched at
anodeinApidae, i.e. in the last common ancestor of the
honey bee Apis mellifera and the bumblebee Bombus ter-
restris. This node marks one of the transitions of solitary
bees to eusocial bees [33]. The overrepresented GO terms
that relate to the evolution of eusociality comprise ’embry-
onic morphogenesis’, ’insulin-like growth factor binding’
and ’regulation of cell growth’ [33] and are additionally
expanded in the species Bombus terrestris and Apis cer-
ana. Insulin and insulin-like signalling (IIS) pathways have
been shown to be differently expressed between castes
in the honeybee and play a role in caste differentiation
[34,35]. Additionally, IIS modifies the behaviour of honey
bee workers in foraging [36]. Functions of some domains
that are associated with overrepresented GO terms can
possibly be related to the emergence of eusociality, either
by being involved in development or have been shown
to be differentially expressed in different castes. Two
domains are associated with growth factors, ’Insulin-like
growth factor binding’ (PF00219) [34,35] and ’EGF-like
domain’ (PF00008). Epidermal growth factor (EGF) has
been shown to be involved in caste differentiation in the
honey bee by knockdown experiments [37,38]. Several
domains have been found to be differentially expressed
in queens and workers in the honey bee and might be
related to eusociality [39], i.e. ’Fibronectin type III domain’
(PF00041), ’Protein kinase domain’ (PF00069), ’Myb-like
DNA-binding domain’ (PF00249) and ’Insect cuticle pro-
tein’ (PF00379). ’Insect cuticle protein’ is also suspected
to play a role in the transition from solitary to eusocial
bees [40].
In comparison to previous studies we can verify some
of the key findings like fusions being the most com-
mon event type accounting for new domain arrangements
[19,20,41]. At the same time we can show to what extent
these findings also apply to other phylogenetic clades or
where differences exist (e.g. single domain loss being the
most common event type in fungi). Comparing the data
basis of this study to previous ones reveals that the total
number of events with a unique solution (Additional file 3)
is much higher than in any previous study, while the
proportion of considered solutions in other studies is sim-
ilar to ours. The underlying total numbers in previous
studies sum up to only a few thousand unique solutions
(5200 in Moore’s pancrustacean set [20]) compared to
ten thousands in this study (24250 in the insect set,
which also contains 18 out of 20 of Moore’s pancrustacean
This increasing total number of resolvable events, while
representing constant proportions over time, suggests
that with increasing quality of sequences, annotations and
motifs in databases we are able to explain more of the evo-
lutionary history, but at the same time add more unknown
or complex cases. However, the ambiguous and complex
solutions we find in this study can be resolved to some
extent with further investigation and approaches specific
for this problem. In some cases, the ambiguity of ambigu-
ous solutions might be resolved by computing domain
trees based on the primary sequences. This is, though,
outside the scope of this study and the information gain
would be minimal as only a very low percentage (5%) of
all solutions are ambiguous ones.
Complex solutions might be resolved with the use of
a deeper and denser phylogeny. Such a phylogeny might
provide additional inner nodes which are required to be
able to track the arrangement changes using single steps.
Another potential way to resolve the underlying molec-
ular rearrangement events of complex gains could be to
consider not only single step events, but also solutions
with two or more steps. However, the latter approach
would strongly increase the complexity of the calcula-
tions, while at the same time introducing uncertainty
by introducing multiple additional ambiguous solution
The GO term enrichment analysis based on domain
changes during evolution can give additionally useful
insights into major functional adaptations of a clade. In
insects for example all described enriched GO terms
(’sensory perception of smell’, ’olfactory receptor activ-
ity’, ’odorant binding’, ’sensory perception of taste’ and
’structural constituent of cuticle’) are essential for commu-
nication between individuals, for example to find mating
partners by sensing pheromones over long distances or
to tell nest mates from potential enemies in social insects
[4244]. For the fungi clade enriched terms are ’carbo-
hydrate metabolic process’ and ’cellulose binding’, which
can be seen as important adaptations for the lifestyle of
some fungal species. Many fungal species (e.g. Serpula
lacrymans) are wood-decaying, for which both metabolic
functions are crucial. Another hint for the wood-decay
related background of these adaptations could be the
enriched GO term ’oxidation-reduction process’, which
can be associated to lignin deconstruction as well as to
cellulose/xylan degradation.
One evolutionary mechanism of specific interest is loss
of function as a process of adaptation. In this study espe-
cially the different signals for losses in plants and fungi
are worth a more detailed investigation. In plants the high
rates of fusion and fission and low rates of losses can
be related to plant specific genome properties. Transpos-
able elements play a major role in plants by the frequent
creation of retrocopies and thus contribute to a high num-
ber of observable gene duplications in plants [4547].
Additionally, many whole genome duplications have been
observed in plants, leading to large genomes as a basis for
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 7 of 13
rearrangements while maintaining the original gene and
function [4749].
A possible explanation for the high frequency of single
domain loss in fungi could be the generally high frac-
tion of single domain arrangements in their proteomes.
Such a high fraction of single domain loss is however not
observed in plants, although eudicots also have a high
fraction of short domain arrangements, comparable to
that of fungi (Additional file 9). The difference between
eudicots and fungi regarding single domain losses can be
explained via the average copy number of single domain
arrangements in both clades. The results of the duplica-
tion count analysis imply that fungi possess by average
just one copy (1.15) of every single domain arrangement,
which can explain the high amount of single domain losses
observed in this clade, while eudicots possess by average
5-6 copies (5.79). From a functional perspective there is
evidence that gene loss plays a particularly important role
in fungi. In fungi, massive gene loss as a major evolution-
ary mechanism has been linked to biotrophy to discard
dispensable genomic components [50] and to adaptations
to new hosts [51]. In addition to some biotrophic species
in our fungi dataset, such as Puccinia graminis [52]or
Ustilago maydis [53], there are other species for which
host adaptations or biotrophy cannot be the explanation
for large-scale gene loss, since they are not biotrophic, like
Saccharomyces cerevisiae. However, for Saccharomyces
species there is evidence for an ancient whole genome
duplication event followed by massive gene loss (an esti-
mated 85%) of the duplicated genes [54]. Next to whole
genome duplication, other studies also linked polyploidy
in fungi and plants to high loss rates [55]. In contrast to
plants, where whole genome duplication events appear
to lead to a high copy number of domains, fungi seem
to possess mechanisms to rapidly reduce their genome
size and throw out redundant or unnecessary information.
The examples suggest that the unusually high rate of sin-
gle domain losses observed in the fungi clade are the result
of a fungi-specific evolutionary mechanism of genome
evolution involving gene loss as a major driving force. In
conclusion, next to genomic properties such as the abun-
dance of duplicates as a basis for subsequent changes
other factors likely play important roles for the evolution-
ary distribution of certain rearrangement events. These
factors can be as described differences in lifestyles, but
also differences in reproduction patterns are potential
candidates, as the presence/absence of sexual reproduc-
tion in many plant and fungal species can provide an
explanation for the observed differences in these clades.
Robustness of results and methodological limitations
Overall, this study shows that only six different basic event
types are sufficient to explain the majority of new domain
arrangements contributing to the complex process of pro-
tein innovation in major phylogenetic clades. The results
are highly consistent across all major clades, i.e. similar
proportions of arrangements can be explained by the same
events across all clades, suggesting that misannotations
do not bias the outcome significantly and the findings
can be considered to be universally valid across eukary-
otes. Furthermore, the similar distribution of events in
insects and eudicots, representing 50% and 70% uniquely
resolved events in the corresponding clade, suggests that
unresolved events in all clades are likely a matter of res-
olution of the tree and not changing the distribution of
events observed in this study. Additionally, the results of
the conducted jackknife test (see Additional file 4)make
sampling biases unlikely.
However, this study focuses on phenotypic changes
through mutational events, which are observable solely
on a domain level. Many of the investigated event types
can be caused by different molecular mechanisms on the
DNA level, which rates can vary compared to each other
and be influenced by lifestyles or reproduction patterns.
For a more complete picture of the evolutionary his-
tory, domain-based methods such as the here presented
one, should be therefore complemented with primary
sequence-based methods to answer specific biological
Future implications and perspectives
Domain-based approaches have some special properties
compared to primary sequence-based ones, making them
particularly suited for different types of analyses. A gen-
eral difference of domain-based approaches is the use of a
larger alphabet with fewer letters per sequence. Addition-
ally, changes on the domain level are less frequent than
mutations of amino acids or nucleotides, why domains are
especially suited for long time scales. The high conser-
vation of domains and a high sensitivity in detection via
their underlying Hidden Markov Models enable the accu-
rate detection of homologous sequence fragments even
in highly diverged sequences. Therefore, domain-based
approaches avoid problems of primary sequence-based
methods as in homology detection. Also, for phylogenetic
analyses there are certain advantages such as reduced
biases through saturation or long branch attraction.
Still, multiple parameters and properties for domain
rearrangements are unknown, limiting the possibilities for
practical implementations of domain-based approaches.
Unfortunately, no general rates and transition probabili-
ties for domain rearrangement events were known before
this study that could be applied to diverse and bigger data
sets. Also time depths for all phylogenies and branches are
not resolvable by now. Despite these limitations, the par-
simony approach used in this study can map the changes
across different speciation events in the tree and shows
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 8 of 13
no significant bias introduced by the method. In fact, as
demonstrated in this study, domain rearrangement rates
hardly depend on depths of single nodes in the phyloge-
netic tree, suggesting the here used parsimony approach
seems to be accurate and resulting in feasible and sub-
stantiated basic rearrangement rates. In a next step these
estimated rates can lay the foundation for more advanced
domain-based methods, while this further step cannot
be provided by this study on its own already. It should
be noticed that the here estimated rates and frequency
of events are the raw descriptive numbers to provide
an unbiased data basis, but for advanced methods these
should be carefully normalised dependent on the scope
of application. The available number of proteins in a
proteome as well as the frequency of duplication events
and therefore active mobile elements in a genome are
for example influencing factors for domain rearrange-
ments and should be taken into account. Additionally,
emergence and loss events in this study are seen from a
functional perspective and the presence or absence of an
arrangement in the protein repertoire is of main interest,
while we do not consider expansions or contractions of
the same arrangement through copy number.
Summarising, this study is meant to elucidate the
dynamics of domain rearrangements in different taxo-
nomic groups and by doing so providing a data basis for
more advanced methods. Analyses from a domain point of
view could complement other methods and make it eas-
ier to estimate biases of other studies or overcome certain
limitations. In conclusion, the results of this study demon-
strate the high potential of domain-based approaches,
while at the same time providing a basis for further devel-
opment in this field.
Data set preparation
Five data sets are analysed in this study, each represent-
ing a different phylogenetic clade: vertebrates (61 species),
insects (72), fungi (36) monocots (19) and eudicots (14)
(see Additional file 11). Only proteomes are included that
haveaDOGMA[56]qualityscore75%, to ensure that
all proteomes used are of high and similar quality. This
prevents the calculation of unduly high number of rear-
rangement events due to poor genome and gene predic-
tion quality. To assure better comparability between the
clades and the species within a clade, the corresponding
ensembl database [57] as a widely used source for com-
parative genomics, was screened primarily for proteomes
when available (fungi, plants(eudicots and monocots) and
As outgroups, a set of five well-annotated species (Ara-
bidopsis thaliana,Caenorhabditis elegans,Drosophila
melanogaster,Homo sapiens and Saccharomyces cere-
visiae) is chosen. For each clade members of the clade
itself are not used as outgroups, for example Drosophila
melanogaster is not used as an outgroup for the insects.
Strigamia maritima is additionally added as outgroup for
the insect clade to make sure insect specific rearrange-
ments are studied and not general arthropod rearrange-
ments. In a first step all but the longest isoform of each
gene is removed from the data set to prevent a bias in
event rate detection by their influence on the analysis.
Proteomes are annotated with Pfam domain models [58]
(version 30) using the script (version 1.5)
provided by Pfam. We used default parameters so that
the script applies the thresholds specified in the Pfam
database for annotating and filtering of the domains. Con-
secutive domain repeats in arrangements are collapsed to
one instance of the domain (A-B-B-B-C A-B-C), as it
has been shown that even between closely related species
copy number of repeated domains can vary a lot [59]and
also to avoid miscalculations due to split domains caused
by annotation/gene model errors.
The phylogenetic tree for the vertebrate clade is taken
from ensembl [57]. The fungi tree is built using NCBI
Taxonomy database [60]andSuperfamily [2]asbasis
and resolving unknown branches from literature [61,62].
The insect tree is built according to the NCBI Taxonomy
database, while multifurcating branches of the genera
Papilio, Apis, Bombus and Dufourea are transformed to
bifurcating solutions according to literature [6366]. Plant
phylogenies are initially inferred using NCBI Taxonomy
and refined using literature [6769]. Next to the quality
criterion mentioned above the resolvability of the phy-
logenetic relationship to other species was the second
crucial criterion for the sampling process. The effect of
subsampling replicates on the analysis is discussed based
on a jackknife test.
Reconstruction of ancestral domain arrangements
The reconstruction of ancestral domain arrangements
and calculation of rates of domain rearrangement
events is carried out using the in-house developed pro-
gram ’DomRates’ (
Reconstruction of ancestral states of domains and
domain arrangements is based on a parsimony principle.
While single domain presence/absence states are usu-
ally better modelled by a Dollo parsimony, multi-domain
arrangements with their modular nature are better mod-
elled by a Fitch parsimony. The assumption underly-
ing the use of Dollo parsimony is that novel domains
are gained only once [16], while arrangements can be
formed and broken several times. For this reason, ’Dom-
Rates’ reconstructs the ancestral states of the whole tree
twice: First with Fitch parsimony for all domain arrange-
ments (including single domain arrangements) and a sec-
ond time with Dollo parsimony for all single domains
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 9 of 13
included in any arrangement (see Fig. 3). The inferred
single domain states with Dollo parsimony are used to
verify all terminal emergence events and single domain
loss/emergence events found by the Fitch parsimony
The copy number of certain domain arrangements
is not considered in DomRates, which means only the
presence/absence of a given arrangement is reconstructed
and taken into account, but not the number of appear-
ances in the proteome. This means that emergence
and loss are seen from a functional perspective in this
study based on if an arrangement is available in the
functional repertoire of a proteome. Expansions and
contractions of the same arrangement regarding the
numbers of its copies are not described as emergence
or loss.
Fig. 3 Reconstruction of ancestral domain content and rearrangement events. Given a known phylogeny and domain annotations of all included
species (a) , it becomes possible to infer six event types leading to new domain contents over time (b). First, the ancestral domain content of all
inner nodes is inferred by two different parsimony approaches: for all single domains using a Dollo parsimony approach (light blue background),
and for all arrangements, using a Fitch parsimony approach (light orange background). In a first traversal from the leaves to the root of the tree, all
inner node states are annotated as present, absent or unknown according to the regarding parsimony rules (c) (see Additional file 1). In a second
traversal from the root to the leaves, the unknown states at the root are first resolved according to the parsimony rules (see Additional file 1)and
subsequently all following unknown states set to the parental state (d). In the reconstructed tree it becomes possible to infer the different event
types at any node by comparison with the parental node (e). In this way emergences/losses of domains are inferred from the Dollo tree, while
arrangements are inferred from the Fitch tree (f)
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 10 of 13
Terms and definitions - event and solution types
Since previous research in the field of protein domains
focused mainly either on emergence and loss of single
domains or on the evolutionary history of whole arrange-
ments, sometimes postulating concepts such as recom-
bination or domain-shuffling, it is necessary to specify
the rearrangement events considered in this study (see
Fig. 3b). In fact, just four biological events can explain the
formation of virtually all domain arrangements: fusion of
existing (ancestral) arrangements (also of single domain
proteins which amounts to gene fusion), fission of exist-
ing (ancestral) domain arrangements, loss of one or more
domains (i.e. there are no traces left as the underly-
ing DNA sequence is for example no longer transcribed)
and emergence of one domain. The latter two biolog-
ical events of loss and emergence can be divided into
two different conceptual ones each. We distinguish in
our study terminal loss/emergence and single domain
loss/emergence, which can be both explained by the
underlying mechanisms for loss and emergence. Termi-
nal events describe the loss or emergence of domains
describe the complete loss or the first emergence of
a single domain as a discrete arrangement. Terminal
loss allows for more than one domain to be lost in
contrast to just one domain considered for terminal
emergence, since terminal loss can easily be caused by
an introduced stop codon, which affects dependent on
the position all following domains in the protein and
not just the next or last domain. With this concep-
tual differentiation we make it possible to combine the
two different approaches of previous studies (loss and
emergence of single domains vs. reshuffling of domain
It is important to note that all mutational events
described here are defined purely on a domain level. On
a DNA level different molecular mechanisms and muta-
tions can lead to the same mutational event described
here (e.g. fusion of two arrangements by fusion of neigh-
boring genes through stop codon loss or through trans-
position of a second gene through mobile elements). For
this reason we just define events we can infer explicitly
on a domain level, while other potential molecular mech-
anisms leading to additional (less common) mutational
events are not considered. An example for this would be
the insertion of a domain/arrangement in the middle of an
existing domain arrangement, which can happen through
crossing over or transposition through smaller mobile ele-
ments, but cannot be distinguished on a domain level
between insertion in the middle of an arrangement or two
subsequent fusion events of independent arrangements.
The possibility of multi step events or multiple possible
solutions makes the definition of different solution types
One can differentiate between four different solu-
tion types (see Additional file 2): exact solution, non-
ambiguous solution, and ambiguous solution can all be
explained by one instance of the single step event types
above, while a complex solution can only be explained
by a chain of the above mentioned events. Exact solu-
tions represent new arrangements that can be explained
by a single event and just this one solution exists. In con-
trast, non-ambiguous solutions describe the case that a
new arrangement can just be explained by one out of
several single events, all of the same type. Ambiguous
solutions involve more than one event type as a possi-
ble explanation for a new arrangement. If there does not
exist a solution in a single step, it is defined as a complex
Domain rearrangement rates calculation
For the rate determination only exact and non-ambiguous
solutions are considered, ambiguous and complex solu-
tions are ignored. To avoid bias introduced by outgroup-
specific arrangements, we exclude the nodes of the out-
group, the root of the complete tree and the root of each
clade (first node after root) from the rate calculation. A
jackknife test with 100 repetitions is carried out by ran-
domly removing 3 species from every clade and rerunning
DomRates on the altered phylogeny to ensure robustness
of the found rates and to identify possible sampling biases
within clades. Means and standard deviation for every
event type frequency in the jackknife test are shown in
Additional file 4.
Enriched gene ontology terms
A Gene Ontology (GO) term enrichment is carried out
with topGO package [70] in R. The GO universe is
composed of all domain arrangements that are present
in all species in a clade as well as the reconstructed
domain arrangements set in the ancestral nodes. Domains
in new domain arrangements that can be explained
by an exact or non-ambiguous solution are annotated
with the ’pfam2go’ mapping of Pfam domains to GO
terms [71]. The enrichment analysis is done using
the ontologies of ’Molecular function’ and ’Biological
process’ and topGOs ’weight01’ algorithm. Significantly
enriched (P-value0.05) GO terms are visualized as tag
Supplementary information
Supplementary information accompanies this paper at
Additional file 1: Rules of inference for both parsimony approaches. The
middle panel shows which two parental states (present, absent or
unknown) for a domain or arrangement lead to which inference in the
child node according to Dollo parsimony (left) or Fitch parsimony (right).
The last line shows to what state an unknown state at the root is resolved.
Dohmen et al. BMC Evolutionary Biology (2020) 20:30 Page 11 of 13
Additional file 2: Solution types. There are four different solution types by
which a new arrangement can be explained. Exact and non-ambiguous
solutions involve each just one event type (see Fig. 3b) and are called
unique solutions. Ambiguous and complex solutions cannot be explained
by a single event type and are called manifold solutions. Just unique
solutions are considered for the rate calculation in this study.
Additional file 3: Total number of events per solution type for all five
Additional file 4: Jackknife test. Mean and standard deviation for all event
type frequencies of a jackknife test with 100 replicates. For the jackknife
test 3 species per clade were randomly removed and the resulting
phylogeny tested with DomRates (100 repetitions).
Additional file 5: Number of rearrangement events across the insect
phylogeny. Digit representation of the total number of rearrangement
events at a specific node is indicated next to the pie chart. For details on
‘Outgroups’ see Methods. Significant GO terms in gained domain
arrangements are shown in a tag cloud (box). GO terms that might point to
insect specific evolution are: chitin metabolic process, sensory perception
of taste.
Additional file 6: Number of rearrangement events across the vertebrate
phylogeny. Digit representation of the total number of rearrangement
events at a specific node is indicated next to the pie chart. For details on
‘Outgroups’ see Methods. Significant GO terms in gained domain
arrangements are shown in a tag cloud (box). GO terms related to
vertebrate evolution are strongly associated with regulation and signal
Additional file 7: Number of rearrangement events across the fungi
phylogeny. Digit representation of the total number of rearrangement
events at a specific node is indicated next to the pie chart. For details on
’Outgroups’ see Methods. Significant GO terms in gained domain
arrangements are shown in a tag cloud (box).
Additional file 8: Number of rearrangement events across the monocot
phylogeny. Digit representation of the total number of rearrangement
events at a specific node is indicated next to the pie chart. For details on
’Outgroups’ see Methods. Significant GO terms in gained domain
arrangements are shown in a tag cloud (box). GO terms that might point to
monocot specific evolution are: ’recognition of pollen’.
Additional file 9: Domain arrangement sizes. The size represents the
number of domains an arrangement consists of, while the fraction relates
to all discriminative domain arrangements in total for the specific clade.
The total number of different arrangements considered in the data sets
was 22199 (vertebrates), 22346 (insects), 10030 (fungi), 15565 (monocots)
and 12097 (eudicots).
Additional file 10: GO term enrichment analysis. Tag cloud for all events
at the root of mammals in the vertebrate tree.
Additional file 11: List of all species included in this study. Furthermore,
for each species the related DOGMA completeness score of their proteome
and version of the used genome assembly is shown.
EGF: Epidermal growth factor; GO: Gene Ontology; IIS: Insulin and insulin-like
signalling; KRTAP: Keratin-associated protein; KRTDAP: Keratinocyte
differentiation-associated protein
We thank Stephen Richards, Richard Gibbs and the i5K pilot initiative for
allowing us to include pre-publication data into our insect data set. For proof
reading and linguistic improvement we want to thank Brennen Heames and
Daniel Dowling.
Authors’ contributions
ED and SK wrote the original draft and performed the formal analysis. ED
developed the software. EBB designed the study and acquired funding. ED, SK,
EBB, SP and CK interpreted the data and revised the manuscript. CK was
responsible for project coordination. All authors approved the final version of
the manuscript.
ED received support by the Deutsche Forschungsgemeinschaft (DFG, German
Research Foundation) – 281125614 / GRK2220. SK was funded by the Leibniz
Graduate School on Genomic Biodiversity Research, grant number “SAW-2013-
ZFMK-4” to EBB. The funding sources played no role in the design of the study,
collection, analysis, and interpretation of data or in writing the manuscript.
Availability of data and materials
The developed software DomRates is available via the project homepage and with full
source code on our gitlab
DomRates/. Furthermore, an archived version of the source code with all data
related to this study (DomRates result files, GOterm analysis, jackknife test) is
available via
implemented in C++ and platform independent, published under the free
GNU GPL licence version 3. For further information please check the
UserManual on the website, where you can find also tutorials and example
data sets to test the software.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1Institute for Evolution and Biodiversity, University of Münster, Hüfferstrasse 1,
48149 Münster, Germany . 2Institute for Bioinformatics and Chemoinformatics,
Westphalian University of Applied Sciences, August-Schmidt-Ring 10, 45665
Recklinghausen, Germany.
Received: 12 April 2019 Accepted: 31 January 2020
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... Domains are structural or functional units of proteins which fold in an independent way [48,49]. Most domains are shared by many proteins and organisms [50], and rearrangements of their order are frequent [51,52]. De novo genes are thought to not contain any known domains [25]. ...
... The observation that proto-genes contain hydrophobic clusters is in agreement with a recent study, in which the authors demonstrated that novel domains were present and evolved in yeast de novo genes [87]. Even if domains are conserved as independent units through evolutionary time and are mainly rearranged, novel domains have been shown to emerge regularly in proteins to add specific novel functionality [52,55]. ...
De novo genes are novel genes which emerge from non-coding DNA. Until now, little is known about de novo genes properties, correlated to their age and mechanisms of emergence. In this study, we investigate four properties: introns, upstream regulatory motifs, 5 prime UTRs and protein domains, in 23135 human proto-genes. We found that proto-genes contain introns, whose number and position correlates with the genomic position of proto-gene emergence. The origin of these introns is debated, as our result suggest that 41% proto-genes might have captured existing introns, as well as the fact that 13.7% of them do not splice the ORF. We show that proto-genes which emerged via overprinting tend to be more enriched in core promotor motifs, while intergenic and intronic ones are more enriched in enhancers, even if the motif TATA is most expressed upstream these genes. Intergenic and intronic 5 prime UTRs of proto-genes have a lower potential to stabilise mRNA structures than exonic proto-genes and established human genes. Finally, we confirm that proto-genes gain new putative domains with age. Overall, we find that regulatory motifs inducing transcription and translation of previously non-coding sequences may facilitate proto-gene emergence. Our paper demonstrates that introns, 5 prime UTRs, and domains have specific properties in proto-genes. We also show the importance of studying proto-genes in relation to their genomic position, as it strongly impacts these properties.
... Domains are structural or functional units of proteins which fold in an independent way and have a characteristic pattern of hydrophobic and polar residues [48,49]. Most domains are shared by many proteins and organisms [50], and rearrangements of their order are frequent [51,52]. Proto-genes are thought not to contain any known domains [25]. ...
... The observation that proto-genes contain hydrophobic clusters is in agreement with a recent study, in which the authors demonstrated that novel domains were present and evolved in yeast de novo genes [88]. Even if domains are conserved as independent units through evolutionary time and are mainly rearranged, novel domains have been shown to emerge regularly in proteins in order to add specific novel functionality [52,55]. ...
Full-text available
De novo genes are novel genes which emerge from non-coding DNA. Until now, little is known about de novo genes’ properties, correlated to their age and mechanisms of emergence. In this study, we investigate four related properties: introns, upstream regulatory motifs, 5′ Untranslated regions (UTRs) and protein domains, in 23,135 human proto-genes. We found that proto-genes contain introns, whose number and position correlates with the genomic position of proto-gene emergence. The origin of these introns is debated, as our results suggest that 41% of proto-genes might have captured existing introns, and 13.7% of them do not splice the ORF. We show that proto-genes which emerged via overprinting tend to be more enriched in core promotor motifs, while intergenic and intronic genes are more enriched in enhancers, even if the TATA motif is most commonly found upstream in these genes. Intergenic and intronic 5′ UTRs of proto-genes have a lower potential to stabilise mRNA structures than exonic proto-genes and established human genes. Finally, we confirm that proteins expressed by proto-genes gain new putative domains with age. Overall, we find that regulatory motifs inducing transcription and translation of previously non-coding sequences may facilitate proto-gene emergence. Our study demonstrates that introns, 5′ UTRs, and domains have specific properties in proto-genes. We also emphasize that the genomic positions of de novo genes strongly impacts these properties.
... DomArchov provides an important contribution for studies that use the DA abstraction as the primary data structure. The DA abstraction is widely used to probe questions of protein evolution, including the co-occurrence and variation in domain repertoire across taxonomic lineages (Cromar et al., 2016;Dohmen et al., 2020;Karev et al., 2004;Tordai et al., 2005;Ye and Godzik, 2004), plasticity in domain order (Bashton and Chothia, 2002;Kummerfeld and Teichmann, 2009;Weiner III et al., 2006), domain occurrence graphs (Cromar et al., 2014;Karev et al., 2002;Przytycka et al., 2006;Vogel et al., 2005), and domain promiscuity, i.e. the propensity of a domain to co-occur with many other domains (Basu et al., 2008(Basu et al., , 2009Cohen-Gihon et al., 2011;Cromar et al., 2014;Marcotte et al., 1999). DomArchov provides, for the first time, a simulation engine to complement such studies. ...
Full-text available
Motivation: Simulation is an essential technique for generating biomolecular data with a 'known' history for use in validating phylogenetic inference and other evolutionary methods. On longer time scales, simulation supports investigations of equilibrium behavior and provides a formal framework for testing competing evolutionary hypotheses. Twenty years of molecular evolution research have produced a rich repertoire of simulation methods. However, current models do not capture the stringent constraints acting on the domain insertions, duplications, and deletions by which multidomain architectures evolve. Although these processes have the potential to generate any combination of domains, only a tiny fraction of possible domain combinations are observed in nature. Modeling these stringent constraints on domain order and co-occurrence is a fundamental challenge in domain architecture simulation that does not arise with sequence and gene family simulation. Results: Here, we introduce a stochastic model of domain architecture evolution to simulate evolutionary trajectories that reflect the constraints on domain order and co-occurrence observed in nature. This framework is implemented in a novel domain architecture simulator, DomArchov, using the Metropolis-Hastings algorithm with data-driven transition probabilities. The use of a data-driven event module enables quick and easy redeployment of the simulator for use in different taxonomic and protein function contexts. Using empirical evaluation with metazoan datasets, we demonstrate that domain architectures simulated by DomArchov recapitulate properties of genuine domain architectures that reflect the constraints on domain order and adjacency seen in nature. This work expands the realm of evolutionary processes that are amenable to simulation. Availability and implementation: DomArchov is written in Python 3 and is available at The data underlying this article are available via the same link. Supplementary information: Supplementary data are available at Bioinformatics online.
... De nombreuses études ont été réalisées ces dernières années pour quantifier et caractériser la nature modulaire de l'évolution des protéines, montrant de cette manière la fréquence des réarrangements architecturaux et des évènements de gain, de perte ou de duplication de domaines protéiques Dohmen et al., 2020;Moore and Bornberg-Bauer, 2012;Stolzer et al., 2015). En effet, de nombreuses protéines, en particulier chez les Eucaryotes, sont composées de plusieurs domaines, combinés à la façon de briques pour créer de nouvelles fonctions (Lees et al., 2016). ...
A l’ère des approches à haut-débit où les flux de données sont abondants, bon nombre de processus restent encore largement inexplorés. Les approches intégratives représentent de nouvelles méthodes de choix pour l’étude de tels systèmes biologiques en permettant leur caractérisation selon plusieurs angles. Dans ce contexte, les travaux de cette thèse ont porté sur l’étude de la multiciliation, processus complexe encore méconnu, par l’intégration de données évolutives et fonctionnelles à plusieurs niveaux de granularité. Après avoir établi un bilan évolutif de la multiciliation, ces travaux ont mené à la conception de BLUR, une nouvelle ressource de génomique comparative conçue pour détecter des divergences de séquence atypiques au sein de familles protéiques à l’échelle d’un protéome complet. Son application à la multiciliation au cours d’une approche intégrative couplant génomique comparative et génomique fonctionnelle a permis d’exploiter la signature évolutive particulière de la multiciliation pour identifier de nouveaux gènes candidats multiciliés.
... Proteins consist of structural domains, which are evolutionarily and functionally conserved units, and fold their tertiary structures independently from the rest of the protein chains [2]. Duplication, deletion or recombination of the genes of domains are the dominant mechanisms to increase the protein repertoire in the process of evolution [3][4][5]. Domain-based protein design, such as domain swapping [6,7], has been used to make chimeric proteins. In principle, domain-based protein design requires much less work than scratch-based protein design, and is more suitable for designing multi-domain protein systems and biomaterials [8]. ...
Full-text available
Protein design has become a powerful method to expand the number of natural proteins and design customized proteins according to demands. Domain-based protein design spares the need to create novel elements from scratch, which makes it a more efficient strategy than scratch-based protein design in designing multi-domain proteins, protein complexes and biomaterials. As the surface shape plays a central role in domain-domain and protein-protein interactions, a global map of the surface shapes of all domains should be very beneficial for domain-based protein design. Therefore, in this study, we characterized the surface shapes of protein domains, collected from CATH and SCOP databases, with their 3D-Zernike descriptors (3DZDs). Then similarities of domain shape features were identified, and all domains were classified accordingly. The preferences of the combinations of domains between different clusters were analyzed in natural proteins from the Protein Data Bank. A user-friendly website, termed CPD3DS, was also developed for storage, retrieval, analyses and visuali-zation of our results. This work not only provides an overall view of protein domain shapes by showing their variety and similarities, but also opens up a new avenue to understand the properties of protein structural domains , and design principles of protein architectures.
... In protein evolution, domains are considered evolutionary modules, and the majority of proteins of all living beings are multi-modular proteins that consist of several domains (Apic et al., 2001). While the creation of multi-modular proteins through shuffling of different domain types has been extensively analyzed (Apic et al., 2001;Björklund et al., 2005;Dohmen et al., 2020), the evolution of proteins made of tandem domain repeats is less understood (Björklund et al., 2006). To get new insights into the functional and structural evolution of these domain repeat proteins, we have focused on the multi-modular metallothioneins (MTs), using those of the fast evolving O. dioica species as case study. ...
Full-text available
Chordate Oikopleura dioica probably is the fastest evolving metazoan reported so far, and thereby, a suitable system in which to explore the limits of evolutionary processes. For this reason, and in order to gain new insights on the evolution of protein modularity, we have investigated the organization, function and evolution of multi-modular metallothionein (MT) proteins in O. dioica. MTs are a heterogeneous group of modular proteins defined by their cysteine (C)-rich domains, which confer the capacity of coordinating different transition metal ions. O. dioica has two MTs, a bi-modular OdiMT1 consisting of two domains (t-12C and 12C), and a multi-modular OdiMT2 with six t-12C/12C repeats. By means of mass spectrometry and spectroscopy of metal-protein complexes, we have shown that the 12C domain is able to autonomously bind four divalent metal ions, although the t-12C/12C pair –as it is found in OdiMT1– is the optimized unit for divalent metal binding. We have also shown a direct relationship between the number of the t-12C/12C repeats and the metal-binding capacity of the MTs, which means a stepwise mode of functional and structural evolution for OdiMT2. Finally, after analyzing four different O. dioica populations worldwide distributed, we have detected several OdiMT2 variants with changes in their number of t-12C/12C domain repeats. This finding reveals that the number of repeats fluctuates between current O. dioica populations, which provides a new perspective on the evolution of domain repeat proteins.
AsymmeTree is a flexible and easy-to-use Python package for the simulation of gene family histories. It simulates species trees and considers the joint action of gene duplication, loss, conversion, and horizontal transfer to evolve gene families along the species tree. To generate realistic scenarios, evolution rate heterogeneity from various sources is modeled. Finally, nucleotide or amino acid sequences (optionally with indels, among-site rate heterogeneity, and invariant sites) can be simulated along the gene phylogenies. For all steps, users can choose from a spectrum of alternative methods and parameters. These choices include most options that are commonly used in comparable tools but also some that are usually not found, such as the innovation model for species evolution. While output files for each individual step can be generated, AsymmeTree is primarily intended to be integrated in complex Python pipelines designed to assess the performance of data analysis methods. It allows the user to interact with, analyze, and possibly manipulate the simulated scenarios. AsymmeTree is freely available on GitHub.
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The emergence of new genes is an important driver of evolutionary novelty. Yet, we lack a conceptual and computational approach that accurately traces gene-family founder events and effectively associates them with trait innovation and major radiation events. Here, we present GenEra, a DIAMOND-fuelled gene-family founder inference framework that addresses previously raised limitations and biases of founder gene detection in genomic phylostratigraphy by accounting for homology detection failure (HDF). We demonstrate how GenEra can accelerate gene-family founder computations from several months to a few days for any query genome of interest. We analyzed 30 genomes to explore the emergence of new gene families during the major evolutionary transitions in plants, animals and fungi. The detection of highly conserved protein domains in these gene families indicates that neofunctionalization of preexisting protein domains is a richer source of gene-family founder events compared with de novo gene birth. We report vastly different patterns of gene-family founder events in animal and fungi before and after accounting for HDF. Only plants exhibit a consistent pattern of founder gene emergence after accounting for HDF, suggesting they are more likely to evolve novelty through the emergence of new genes compared to opisthokonts. Finally, we show that the transition to multicellularity in streptophytes, the terrestrialization of land plants and the origin of angiosperms are associated with gene-family founder bursts, as well as the evolution of bilateral symmetry in animals.
How do proteins evolve? How do changes in sequence mediate changes in protein structure, and in turn in function? This question has multiple angles, ranging from biochemistry and biophysics to evolutionary biology. This review provides a brief integrated view of some key mechanistic aspects of protein evolution. First, we explain how protein evolution is primarily driven by randomly acquired genetic mutations and selection for function, and how these mutations can even give rise to completely new folds. Then, we also comment on how phenotypic protein variability, including promiscuity, transcriptional and translational errors, may also accelerate this process, possibly via “plasticity‐first” mechanisms. Finally, we highlight open questions in the field of protein evolution, with respect to the emergence of more sophisticated protein systems such as protein complexes, pathways, and the emergence of pre‐LUCA enzymes.
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Diverse studies have shown that the content of genes present in sequenced genomes does not seem to correlate with the complexity of the organisms. However, various studies have shown that organism complexity and the size of the proteome has, indeed, a significant correlation. This characteristic allows us to postulate that some molecular mechanisms have permitted a greater functional diversity to some proteins to increase their participation in developing organisms with higher complexity. Among those mechanisms, the domain promiscuity, defined as the ability of the domains to organize in combination with other distinct domains, is of great importance for the evolution of organisms. Previous works have analyzed the degree of domain promiscuity of the proteomes showing how it seems to have paralleled the evolution of eukaryotic organisms. The latter has motivated the present study, where we analyzed the domain promiscuity in a collection of 84 eukaryotic proteomes representative of all the taxonomy groups of the tree of life. Using a grammar definition approach, we determined the architecture of 1,223,227 proteins, conformed by 2,296,371 domains, which established 839,184 bigram types. The phylogenetic reconstructions based on differences in the content of information from measures of proteome promiscuity confirm that the evolution of the promiscuity of domains in eukaryotic organisms resembles the evolutionary history of the species. However, a close analysis of the PHD and RING domains, the most promiscuous domains found in fungi and functional components of chromatin remodeling enzymes and important expression regulators, suggests an evolution according to their function.
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The last few years have witnessed significant changes in Pfam ( The number of families has grown substantially to a total of 17,929 in release 32.0. New additions have been coupled with efforts to improve existing families, including refinement of domain boundaries, their classification into Pfam clans, as well as their functional annotation. We recently began to collaborate with the RepeatsDB resource to improve the definition of tandem repeat families within Pfam. We carried out a significant comparison to the structural classification database, namely the Evolutionary Classification of Protein Domains (ECOD) that led to the creation of 825 new families based on their set of uncharacterized families (EUFs). Furthermore, we also connected Pfam entries to the Sequence Ontology (SO) through mapping of the Pfam type definitions to SO terms. Since Pfam has many community contributors, we recently enabled the linking between authorship of all Pfam entries with the corresponding authors' ORCID identifiers. This effectively permits authors to claim credit for their Pfam curation and link them to their ORCID record.
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Around 150 million years ago, eusocial termites evolved from within the cockroaches, 50 million years before eusocial Hymenoptera, such as bees and ants, appeared. Here, we report the 2-Gb genome of the German cockroach, Blattella germanica, and the 1.3-Gb genome of the drywood termite Cryptotermes secundus. We show evolutionary signatures of termite eusociality by comparing the genomes and transcriptomes of three termites and the cockroach against the background of 16 other eusocial and non-eusocial insects. Dramatic adaptive changes in genes underlying the production and perception of pheromones confirm the importance of chemical communication in the termites. These are accompanied by major changes in gene regulation and the molecular evolution of caste determination. Many of these results parallel molecular mechanisms of eusocial evolution in Hymenoptera. However, the specific solutions are remarkably different, thus revealing a striking case of convergence in one of the major evolutionary transitions in biological complexity.
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Repeats are ubiquitous elements of proteins and they play important roles for cellular function and during evolution. Repeats are, however, also notoriously difficult to capture computationally and large scale studies so far had difficulties in linking genetic causes, structural properties and evolutionary trajectories of protein repeats. Here we apply recently developed methods for repeat detection and analysis to a large dataset comprising over hundred metazoan genomes. We find that repeats in larger protein families experience generally very few insertions or deletions (indels) of repeat units but there is also a significant fraction of noteworthy volatile outliers with very high indel rates. Analysis of structural data indicates that repeats with an open structure and independently folding units are more volatile and more likely to be intrinsically disordered. Such disordered repeats are also significantly enriched in sites with a high functional potential such as linear motifs. Furthermore, the most volatile repeats have a high sequence similarity between their units. Since many volatile repeats also show signs of recombination, we conclude they are often shaped by concerted evolution. Intriguingly, many of these conserved yet volatile repeats are involved in host-pathogen interactions where they might foster fast but subtle adaptation in biological arms races. Key Words: protein evolution, domain rearrangements, protein repeats, concerted evolution.
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The Ensembl gene annotation system has been used to annotate over 70 different vertebrate species across a wide range of genome projects. Furthermore, it generates the automatic alignment-based annotation for the human and mouse GENCODE gene sets. The system is based on the alignment of biological sequences, including cDNAs, proteins and RNA-seq reads, to the target genome in order to construct candidate transcript models. Careful assessment and filtering of these candidate transcripts ultimately leads to the final gene set, which is made available on the Ensembl website. Here, we describe the annotation process in detail. Database URL:
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Motivation: Genome studies have become cheaper and easier than ever before, due to the decreased costs of high-throughput sequencing and the free availability of analysis software. However, the quality of genome or transcriptome assemblies can vary a lot. Therefore, quality assessment of assemblies and annotations are crucial aspects of genome analysis pipelines. Results: We developed DOGMA, a program for fast and easy quality assessment of transcriptome and proteome data based on conserved protein domains. DOGMA measures the completeness of a given transcriptome or proteome and provides information about domain content for further analysis. DOGMA provides a very fast way to do quality assessment within seconds. Availability and implementation: DOGMA is implemented in Python and published under GNU GPL v.3 license. The source code is available on Contact: e.dohmen{at}, c.kemena{at} Supplementary Information: Supplementary data are available at Bioinformatics online.
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Understanding the evolution of animal societies, considered to be a major transition in evolution, is a key topic in evolutionary biology. Recently, new gateways for understanding social evolution have opened up due to advances in genomics, allowing for unprecedented opportunities in studying social behavior on a molecular level. In particular, highly eusocial insect species (caste-containing societies with non-reproductives that care for siblings) have taken center stage in studies of the molecular evolution of sociality. Despite advances in genomic studies of both solitary and eusocial insects, we still lack genomic resources for early insect societies. To study the genetic basis of social traits requires comparison of genomes from a diversity of organisms ranging from solitary to complex social forms. Here we present the genome of a subsocial bee, Ceratina calcarata. This study begins to address the types of genomic changes associated with the earliest origins of simple sociality using the small carpenter bee. Genes associated with lipid transport and DNA recombination have undergone positive selection in C. calcarata relative to other bee lineages. Further, we provide the first methylome of a non-eusocial bee. C. calcarata contains the complete enzymatic toolkit for DNA methylation. As in the honey bee and many other holometabolous insects, DNA methylation is targeted to exons. The addition of this genome allows for new lines of research into the genetic and epigenetic precursors to complex social behaviors.
Domains are the functional building blocks of proteins. In this work we discuss how domains can contribute to the evolution of new functions. Domains themselves can evolve through various mechanisms, altering their intrinsic function. Domains can also facilitate functional innovations by combining with other domains to make novel proteins. We discuss the mechanisms by which domain and domain combinations support functional innovations. We highlight interesting examples where changes in domain combination promote changes at the domain level.
Ancient duplication events and a high rate of retention of extant pairs of duplicate genes have contributed to an abundance of duplicate genes in plant genomes. These duplicates have contributed to the evolution of novel functions, such as the production of floral structures, induction of disease resistance, and adaptation to stress. Additionally, recent whole-genome duplications that have occurred in the lineages of several domesticated crop species, including wheat (Triticum aestivum), cotton (Gossypium hirsutum), and soybean (Glycine max), have contributed to important agronomic traits, such as grain quality, fruit shape, and flowering time. Therefore, understanding the mechanisms and impacts of gene duplication will be important to future studies of plants in general and of agronomically important crops in particular. In this review, we survey the current knowledge about gene duplication, including gene duplication mechanisms, the potential fates of duplicate genes, models explaining duplicate gene retention, the properties that distinguish duplicate from singleton genes, and the evolutionary impact of gene duplication.
The recent increase in genomic data is revealing an unexpected perspective of gene loss as a pervasive source of genetic variation that can cause adaptive phenotypic diversity. This novel perspective of gene loss is raising new fundamental questions. How relevant has gene loss been in the divergence of phyla? How do genes change from being essential to dispensable and finally to being lost? Is gene loss mostly neutral, or can it be an effective way of adaptation? These questions are addressed, and insights are discussed from genomic studies of gene loss in populations and their relevance in evolutionary biology and biomedicine.