Rainer Melzer

University College Dublin | UCD · School of Biology and Environmental Science

The word ‘fruit’ is derived from the latin ‘fructus’ which itself is said to be derived from ‘frui’, which means to enjoy. Along those lines, I hope this year’s Flowering Newsletter brings a lot of joy, because fruits and seeds feature in multiple articles.

Hemp ( Cannabis sativa L.) is an extraordinarily versatile crop, with applications ranging from medicinal compounds to seed oil and fibre products. Cannabis sativa is a short-day plant, and its flowering is tightly controlled by photoperiod. However, substantial genetic variation exists for photoperiod sensitivity in C. sativa, and photoperiod-inse...

Hemp (Cannabis sativa) is a highly versatile crop with a multitude of applications, from textiles, biofuel and building material to high‐value food products for consumer markets. Furthermore, non‐hallucinogenic cannabinoids like cannabidiol (CBD), which can be extracted from female hemp flowers, are potentially valuable pharmacological compounds. I...

Hemp ( Cannabis sativa ) is a highly versatile multi-purpose crop with a multitude of applications, from textiles, biofuel and building material to high-value food products for consumer markets. Furthermore, non-hallucinogenic cannabinoids like cannabidiol (CBD), which can be extracted from female hemp flowers, are potentially valuable pharmacologi...

Identifying how various components of climate change will influence ecosystems and vegetation subsistence will be fundamental to mitigate negative effects. Climate change-induced waterlogging is understudied in comparison to temperature and CO2. Grasslands are especially vulnerable through the connection with global food security, with perennial ry...

Cannabis sativa is most prominent for its psychoactive secondary compound tetrahydrocannabinol, or THC. However, THC is only one of many phytocannabinoids found in this (in)famous medicinal plant. The stepwise legalization of Cannabis in many countries has opened opportunities for its medicinal and commercial use, sparking scientific interest in th...

Identifying how various components of climate change will influence ecosystems and vegetation subsistence will be fundamental to mitigate negative effects. Climate change-induced waterlogging is understudied in comparison to temperature and CO2. Grasslands are especially vulnerable through the connection with global food security, with perennial ry...

Cannabis sativa is well known for its production of psychoactive chemicals and medicinal products, but it also has huge potential to be a multipurpose crop. Cultivated for biofuel, building materials and textiles, Cannabis has a high carbon sequestration rate and is bound to be a key player in future sustainable agriculture. The distinct applicatio...

Cannabis sativa is an extraordinarily versatile species. Hemp and its cousin marijuana, both C. sativa, have been used for millennia as a source of fibre, oil, and for medicinal, spiritual, and recreational purposes. Because the consumption of Cannabis can have psychoactive effects, the plant has been widely banned throughout the last century. In t...

Key message We studied the DNA-binding profile of the MADS-domain transcription factor SEPALLATA3 and mutant variants by SELEX-seq. DNA-binding characteristics of SEPALLATA3 mutant proteins lead us to propose a novel DNA-binding mode. Abstract MIKC-type MADS-domain proteins, which function as essential transcription factors in plant development, b...

Cannabis sativa is an extraordinarily versatile species. Hemp and its cousin marijuana, both C. sativa, have been used for millennia as a source of fibre, oil and for medicinal, spiritual and recreational purposes. Because the consumption of Cannabis can have psychoactive effects, the plant has been widely banned throughout the last century. In the...

To better adapt transiently or lastingly to stimuli from the surrounding environment, the chromatin states in plant cells vary to allow the cells to fine-tune their transcriptional profiles. Modifications of chromatin states involve a wide range of post-transcriptional histone modifications, histone variants, DNA methylation, and activity of non-co...

Schilling et al. introduce and discuss Cannabis.

This article comments on: García A, Aguado E, Martínez C, Loska D, Beltrán S, Valenzuela JL, Garrido D, Jamilena M. 2019. The ethylene receptors CpETR1A and CpETR2B cooperate in the control of sex determination in Cucurbita pepo. Journal of Experimental Botany 70, 154–167.

Wheat ( Triticum aestivum ) is one of the most important crops worldwide. Given a growing global population coupled with increasingly challenging cultivation conditions, facilitating wheat breeding by fine‐tuning important traits is of great importance. MADS ‐box genes are prime candidates for this, as they are involved in virtually all aspects of...

Mineral nutrient supply can affect the hydraulic property of roots. The aim of the present work on sheepgrass (Leymus chinensis L.) plants was to test whether any changes in root hydraulic conductivity (Lp; exudation analyses) in response to a growth‐limiting supply of phosphate (P) are accompanied by changes in (1) cell Lp via measuring the cell p...

Background Wheat ( Triticum aestivum ) is one of the most important crops worldwide. Given a growing global population coupled with increasingly challenging climate and cultivation conditions, facilitating wheat breeding by fine-tuning important traits such as stress resistance, yield and plant architecture is of great importance. Since they are in...

SEPALLATA3 of Arabidopsis thaliana is a MADS‐domain transcription factor and a key regulator of flower development. MADS‐domain proteins bind to sequences termed ‘CArG‐boxes’ (consensus 5′‐CC(A/T)6GG‐3′). Since only a fraction of the CArG‐boxes in the Arabidopsis genome are bound by SEPALLATA3, more elaborate principles have to be discovered to bet...

The sections in this article are Introduction ABC : Early Genetic Models of Floral Organ Identity From the ABC to the ABCDE Model Elective Affinities of Homeotic Proteins: The Floral Quartet Model Beyond the Floral Quartets Sensu Stricto : Multimeric Complexes of Other MIKC ‐Type Proteins Outlook: The Devil is Always in the Details – What We...

MADS-box genes are key regulators of virtually every aspect of plant reproductive development. They play especially prominent roles in flowering time control, inflorescence architecture, floral organ identity determination, and seed development. The developmental and evolutionary importance of MADS-box genes is widely acknowledged. However, their r...

The development of angiosperm flowers is regulated by homeotic MIKC-type MADS-domain transcription factors that activate or repress target genes via the formation of DNA-bound, organ specific tetrameric complexes. The protein-protein interaction (PPI) capabilities differ considerably between different MIKC-type proteins. The floral homeotic protein...

The development of angiosperm flowers is regulated by homeotic MIKC-type MADS-domain transcription factors that activate or repress target genes via the formation of DNA-bound, organ specific tetrameric complexes. The protein-protein interaction (PPI) capabilities differ considerably between different MIKC-type proteins. The floral homeotic protein...

This article comments on: Capovilla G, Symeonidi E, Wu R, Schmid M. 2017. Contribution of major FLM isoforms to temperature-dependent mediated flowering in Arabidopsis thaliana. Journal of Experimental Botany 68, 5117–5127.

SEPALLATA3 of Arabidopsis thaliana is a MADS-domain transcription factor and a central player in flower development. MADS-domain proteins bind as dimers to AT-rich sequences termed ‘CArG-boxes’ which share the consensus 5’-CC(A/T) 6 GG-3’. Since only a fraction of the abundant CArG-boxes in the Arabidopsis genome are bound by SEPALLATA3, more elabo...

The floral quartet model of floral organ specification poses that different tetramers of MIKC-type MADS-domain transcription factors control gene expression and hence the identity of floral organs during development. Here, we provide a brief history of the floral quartet model and review several lines of recent evidence that support the model. We a...

Background How the diversity of life on our planet originated is not completely understood and many questions are still open. Especially, the role of developmental robustness in evolution is an often neglected topic. Scope Considering diverse groups of plants and animals, and employing different concepts and approaches, the authors of articles in...

Background: The origin of new species and of new forms is one of the fundamental characteristics of evolution. However, the mechanisms that govern the diversity and disparity of lineages remain poorly understood. Particularly unclear are the reasons why some taxa are vastly more species-rich than others and the manner in which species diversity an...

Phytoplasmas are pathogenic bacteria that reprogram plant development such that leaf-like structures instead of floral organs develop. Infected plants are sterile and mainly serve to propagate phytoplasmas and thus have been termed 'zombie plants'. The developmental reprogramming relies on specific interactions of the phytoplasma protein SAP54 with...

In plants, MADS domain transcription factors act as central regulators of diverse developmental pathways. In Arabidopsis thaliana, one of the most central members of this family is SEPALLATA3 (SEP3), which is involved in many aspects of plant reproduction, including floral meristem and floral organ development. SEP3 has been shown to form homo and...

The SEPALLATA (SEP) genes of Arabidopsis thaliana encode MADS-domain transcription factors that specify the identity of all floral organs. The four Arabidopsis SEP genes function in a largely yet not completely redundant manner. Here, we analysed interactions of the SEP proteins with DNA. All of the proteins were capable of forming tetrameric quart...

Background and Aims DEFICIENS (DEF)- and GLOBOSA (GLO)-like proteins constitute two sister clades of floral homeotic transcription factors that were already present in the most recent common ancestor (MRCA) of extant angiosperms. Together they specify the identity of petals and stamens in flowering plants. In core eudicots, DEF- and GLO-like protei...

Flower development is under strict genetic control and hence proceeds in a highly standardized way. It can be subdivided into several major steps, such as floral induction, floral meristem formation, and floral organ development. Accurate control of the different steps of flower development is achieved by a gene regulatory network (GRN) that is com...

The products of B class floral homeotic genes specify petal and stamen identity, and loss of B function results in homeotic conversions of petals into sepals and stamens into carpels. Here, we describe the molecular characterization of seirena-1 (sei-1), a mutant from the basal eudicot California poppy (Eschscholzia californica) that shows homeotic...

In the model plant Arabidopsis thaliana, a core eudicot, the floral homeotic C-class gene AGAMOUS (AG) has a dual role specifying reproductive organ identity and floral meristem determinacy. We conduct a functional analysis of the putative AG ortholog ThtAG1 from the ranunculid Thalictrum thalictroides, a representative of the sister lineage to all...

All major processes of life depend on differential gene expression, which is largely controlled by the activity of transcription factors (TFs). In plants many TFs are encoded by members of multigene families that expanded much more dramatically during land plant evolution than during the evolution of animals and fungi. Here we review typical featur...

Background and Aims Homeotic transitions are usually dismissed by population geneticists as credible modes of evolution due to their assumed negative impact on fitness. However, several lines of evidence suggest that such changes in organ identity have played an important role during the origin and subsequent evolution of the angiosperm flower. Bet...

Several lines of evidence suggest that the identity of floral organs in angiosperms is specified by multimeric transcription factor complexes composed of MADS-domain proteins. These bind to specific cis-regulatory elements ('CArG-boxes') of their target genes involving DNA-loop formation, thus constituting 'floral quartets'. Gymnosperms, angiosperm...

MIKC-type MADS domain proteins are key regulators of flower development in angiosperms. B(sister) genes constitute a clade with a close relationship to class B floral homeotic genes, and have been conserved for more than 300 million years. The loss-of-function phenotype of the A. thaliana B(sister) gene ABS is mild: mutants show reduced seed colora...

20 years after establishment of the ABC model many of the molecular mechanisms underlying development of the angiosperm flower are relatively well understood. Central players in the gene regulatory network controlling flower development are SQUA-like, DEF/GLO-like, AG-like and AGL6/SEP1-like MIKC-type MADS-domain transcription factors. These provid...

Homeotic MADS box genes encoding transcription factors specify the identity of floral organs by interacting in a combinatorial way. The ‘floral quartet model’, published several years ago, pulled together several lines of evidence suggesting that floral homeotic proteins bind as tetramers to two separated DNA sequence elements termed ‘CArG boxes’ b...

The organs of a eudicot flower are specified by four functional classes, termed class A, B, C and E, of MADS domain transcription factors. The combinatorial formation of tetrameric complexes, so called ‘floral quartets’, between these classes is widely believed to represent the molecular basis of floral organ identity specification. As constituents...

IntroductionABC: early genetic models of floral organ identityFrom the ABC to the ABCDE modelElective affinities of homeotic proteins: the floral quartet modelBeyond the floral quartets sensu stricto: multimeric complexes of other MIKC-type proteinsOutlook: the devil is always in the details - what we still don't know about floral quartetsSummaryAc...

Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model speci...

Interactions of floral homeotic genes have so far mainly been defined genetically and in terms of protein complex formation. However, to better understand the molecular evolutionary dynamics of the network controlling floral organ identity, its complete “hard‐wiring” has to be determined, that is, the physiochemical interactions on which floral hom...

MIKC-type proteins represent a class of MADS-domain transcription factors and are defined by a unique domain structure: in addition to the highly conserved DNA-binding MADS-domain, they have three other domains ('I', 'K' and 'C'), with the keratin-like K-domain being the most highly conserved and characteristic one. The number and functional divers...