Maintenance and Function of Barley Shoot Meristems

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Establishment, maintenance and termination of plant shoot meristems has been extensively studied in eudicots such as Arabidopsis, and gene regulatory networks that adjust the activities of these complex stem cell niches during changing growth periods have been elucidated. The architecture of grass and their complex inflorescences is very distinct, and relies upon diversified meristems whose regulation and functions have not yet been elucidated. Studies in maize and rice previously showed that some of the key signalling pathways and transcription factor networks which were found to control Arabidopsis meristem development are only partially conserved in grasses. Despite their enormous importance for a more fundamental conceptual understanding of plant stem cell systems, cereal stem cell systems still represent an underexplored territory. We have started to investigate barley meristem and stem cell regulation using our knowledge on Arabidopsis signalling pathways as a starting point. We found that a CLAVATA-like signalling pathway operates also in barley, and controls the proliferation of different meristems in the barley inflorescence. We used a targeted mutagenesis strategy to generate mutants for multiple receptor kinases that act in stem cell regulation, and started to study their expression patterns. Our preliminary data indicate that conserved peptide activated receptor kinase signalling pathways control growth and differentiation in the diverse barley meristems, but that their regulation, expression patterns and their integration into plant development is very distinct and specialised for grasses. We propose here to explore the functions of CLE peptide and CLAVATA-family receptor signalling in barley stem cell systems using induced mutations and expression studies, and generate single cell RNA sequencing information for the different above-ground meristem types to identify their characteristic gene expression profiles. By integrating our results with those of our consortium partners that are working on closely related aspects of stem cell regulation in barley, maize and Brachypodium, we will jointly develop a deeper understanding of stem cell systems of cereal plants.