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Insights into Growth Regulation
by Connecting Simulations of Plant-Growth to the Plant Gall Life Cycle
Richard W. van Nieuwenhovena, Florian Gisingera, Pia-Marie Gravesa, August Hammela, Matthias M¨
ortha, Ille C. Gebeshubera
Acknowledgements: Friedrich W. Aumayra, Michael Kiehnb, Frank Schumacherb, Regina Kramerc
aE134-03, Institute of Applied Physics, TU Wien, Vienna, Austria bCore Facility Botanischer Garten, Universit¨
at Wien, Vienna, Austria, cForschung & Artenschutz,Tiergarten Sch ¨
onbrunn, Vienna, Austria
Introduction
Fig. 1 Very old trees still
produce perfect young leaves.
Plantae (plants) merely use
readily available resources
and can cover all their needs
from their local environment
(Fig. 1) [1].
Sustainable production by
controlling the growth and us-
ing the restoration capabilities
of plants has the potential to
solve many problems humanity
currently faces.
Multiple non-plant organisms
have developed ways to manipulate the growth of plants to
their advantage [2]. Among them are gall wasps (Fig. 2),
which can reprogram plants that then grow tailored breeding
chambers using biochemical substances [4].
5 mm
Fig. 2 The asexual (agamic)
generation gall of Cynips
quercusfolii [3].
Understanding the mechanisms
the gall wasps use for this
manipulation is a major step in
developing ways to gain control
over the development of plant-
based organisms.
Previous studies are making
progress in understanding the
mechanism from the cellular
and biochemical viewpoints.
Connecting this microbiological
knowledge to macro biology is
highly complex because of various interconnected parameters.
Macrobiology - Background
When the effectors take over the plant growth, galls are
formed in all kinds of shapes to create an environment for the
eggs to hatch and the larvae to develop. Their morphology
usually differ-from other structures formed by the plant itself [4].
Fig. 3 Gall wasp live-cycle
adapted from [3].
Gall wasps stick fertilized eggs
onto young oak leaves. Af-
ter hatching, the larvae de-
posit saliva, which contains
gall formation inducing effec-
tors. The gall provides the
larvae with nutrients until the
tree sheds its leaves in au-
tumn. Then the larvae pupate,
and in February, female gall
wasps hatch, which lay unfertil-
ized eggs, from which another
type of galls develop. In late
spring, gall wasps hatch and mate, starting the life-cycle again
(Fig. 3) [2].
Microbiology - Background
The gall formation inducing effectors are believed to
be a combination of i.a., enzymes, proteins and phyto-
hormones that locally manipulate cell growth and division.
Fig. 4 Ribosome produce
proteins regulated by the
availabe mRNA. (own image)
Genes expression that such ef-
fectors regulate in galls seem to
be upregulated, as indicated by
transcriptome analysis (Fig. 4).
There is evidence that >30
genes are upregulated during
gall growth and several possible
effectors have been identified. It
is still unclear whether they have
a direct impact on gall growth as
the molecular and cellular mech-
anisms of gall development remain largely unknown [4].
Why use Growth Algorithms
The development of plants over their lifespan is a highly
complex, continuous process. The ability to keep producing
new structures such as leaves and branches, regardless of
their age, is especially notable. Developing growth simulation
algorithms furthers our understanding of the driving forces
behind this process. This study combines recent advances in
growth algorithms with detailed observations of gall growth in
Nature to understand the conditions necessary to grow a gall-
like structure from a leaf.
1 cm
Time-lapse Observation w/ Plant Spy
Galls are observed using a Raspberry Pi Zero W mini
computer system (Fig. 5) in a tube casing. With the help
of a real-time clock, two cameras mounted on a 3D printed
construction take images of a gall twice a day from both the top
and the underside of the leaf. The pictures are uploaded to the
cloud. Additionally, environmental sensors record temperature,
pressure, light intensity and humidity. The time-lapse recordings
shall give insight to the growth of the gall and set border
conditions for the algorithms.
LiPo SHIM
(Battery)
RtcPower
Control
Raspberry
Pi Zero
I2C
sensors
Multy
Camera
Top
Camera
Back
Camera
Mobile
Internet
Fig. 5 Block diagram of the observation unit based on a
Rapberry Pi Zero W mini computer system.
Growth Algorithms
Describing the highly complex growth of liv-
ing organisms has proven to be an impor-
tant method for understanding the underly-
ing biological mechanisms. Plant growth
simulation algorithms are increasingly suc-
cessfully describing plant growth. Virtual-
Leaf [5] is one of the frameworks successfully
used for modeling plant and tissue growth.
Fig. 6 Simulation
snapshot of a leaf
model [6].
The latest develop-
ments in using growth
algorithms to develop
leaves can reproduce
the maturing of a leaf
(Fig. 6) [6]. The exist-
ing algorithm is based
on a single layer 2D
model of cells and
their interactions. We
will extend the model
to multiple layers and
advance to a 2.5D representation.
Introducing Disturbance
We introduce a disturbance to the algorithm
in the nearly matured leaf and use the gall
growth observations as boundary conditions.
Fig. 7 Disturbance in a 2
layer 2.5D model. (own
image)
Reducing the
added distur-
bance to a
minimum will
give insight into
the biological
control neces-
sary to direct
the growth of
leaves into the
development
of gall-like
structures. By
including sticky
interconnections between the layers, the
layers can bulge. Such a 2.5D model of a 3D
structure can be constructed using bulging as
a virtual dimension. The introduced distur-
bance can now trigger bulging and new sticky
interconnections that form gall-like structures
(Fig. 7).
Outlook
Fig. 8 Plant
Spy.
Currently we are setting up
the Plant Spy and observation
protocols to collect growth data
over the development life cycle
of galls (Fig. 8). As a next
step we will extend the leaf
algorithm to support two con-
nected layers so that the Monte-
Carlo model is able to transport
pressures between layers over
the interconnections. The re-
sulting disturbance which is
necessary to induce the con-
struction of a gall-like struc-
ture can help deepen our un-
derstanding of the microbio-
logical processes necessary to cause such
structural changes.
References
[1] Jan Baptist van Helmont. Front Matter.Elsevier, 1652. ISBN: 978-1-4933-0398-4.
[2] Margaret Redfern. Plant Galls.Collins, Apr. 28, 2011. ISBN: 978-0008175122.
[3] Sally Jennings. NATT-at-NKM.Oct. 26, 2015. URL:
https://www.flickr.com/photos/75001205@N02/with/48918989092/.
[4] Seiji Takeda et al. “Recent Progress Regarding the Molecular Aspects of Insect Gall Formation”. In: International
Journal of Molecular Sciences 22 (17) (Aug. 2021), p. 9424. DOI:10.3390/ijms22179424.URL:
https://doi.org/10.3390/ijms22179424.
[5] Roeland Merks and Michael Guravage. VirtualLeaf.Version 1.02. Aug. 17, 2021. URL:
https://github.com/rmerks/VirtualLeaf2021.
[6] Dirk De Vos et al. “Simulating leaf growth dynamics through Metropolis-Monte Carlo based energy minimization”.
In: Journal of Computational Science 9 (July 2015), pp. 107–111. DOI:10.1016/j.jocs.2015.04.026.URL:
https://doi.org/10.1016/j.jocs.2015.04.026.
Contact the Authors
Richard W. van Nieuwenhoven
nieuwenhoven@iap.tuwien.ac.at
August Hammel
hammel@iap.tuwien.ac.at
Florian Gisinger
gisinger@iap.tuwien.ac.at
Pia-Marie Graves
graves@iap.tuwien.ac.at
Matthias M¨
orth
moerth@iap.tuwien.ac.at
Prof. Ille C. Gebeshuber
gebeshuber@iap.tuwien.ac.at
Engineered Living
Materials
Saarbr¨
ucken, Germany
June, 2022
