Coordination Funds

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Plant meristems are major determinants of plant architecture, plant diversification and acclimation to environmental stresses. Moreover, meristems are fundamentally important for the productivity of crop plants as they directly determine yield. The vegetative meristems determine the basic plant body plan and produce all above- and below-ground parts of plants. Regulated by flowering time checkpoints, vegetative meristems transit to reproductive meristems forming sexual organs and germ cells. Work in the model plant Arabidopsis revealed that meristems are organized by stem cell niches consisting of rarely dividing organizing cells, which are surrounded by stem cells. Stem cell niches in this species are regulated by negative-feedback loops of stem cell promoting factors and mobile ligands that are perceived by receptor kinases.In contrast to Arabidopsis, the shoot and root architectures of grasses (cereals) including the economically important crops maize, wheat, rice and barley are very complex. Grasses generate larger vegetative meristems, produce additional organs like seminal and crown root as well as highly complex inflorescence meristems with meristem types absent in eudicots. Mutations in genes controlling grass meristem functions have played key roles during crop domestication. Despite their economic importance, our understanding of meristem development and the organization of cereal stem cell systems is very limited. Studies reported so far indicated that paradigms based on studies using Arabidopsis are not universally applicable.The goal of research unit FOR5235 is to further our understanding of the complex signaling and gene regulating networks and their interaction that determine meristem establishment, maintenance and termination in the two major cereal families. With a focus on maize as an example for a tropical cereal crop (Panicoideae), barley as an example for a temperate cereal crop (Pooideae) and its close relative model grass Brachypodium, the PIs of FOR5235 will combine their complementing expertise, research interest and resources to test a number of working hypothesis. They especially aim to explore whether the complex meristems of cereals are based on conserved but strongly modified, or also on novel signaling pathways and associated gene regulatory networks. Major novel insights are expected due to the holistic and comparative approach to generate gene expression and marker atlases from all major cereal meristems and their stem cell systems. Novel stem cell genes will be identified that are highly relevant for further crop improvement. The jointly developed toolkit and identified novel genes will be used and extended in the anticipated second funding period to deepen our understanding about cereal stem cell systems, but especially to understand also genetic variation and environmental aspects modulating the systems.