Inflorescence and spikelet meristem establishment and maintenance in barley

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Inflorescence architecture controls flower and hence seed production and is largely defined by meristem identity and determinacy decisions. Grass inflorescence meristems (IM) produce a unique structure, spikelet meristems (SM) that then produce floral meristems (FM), flowers, and seeds. How the establishment, maintenance, and termination of these different meristems within the inflorescence are genetically controlled in the temperate cereal barley is not well understood.We have identified and described three different transcription factors that control meristem determinacy and identity transitions and thereby the number of spikelets and flowers produced on the barley spike. CENTRORADIALIS (CEN) and INTERMEDIUM-M/DOUBLE SEED 1 (INT-M/DUB1) promote IM indeterminacy and spikelet meristem (SM) determinacy, while FLOWERING LOCUS T1 (FT1) promotes IM determinacy and SM indeterminacy. These results suggest that IM and SM determinacy are genetically coordinated and negatively correlated in barley. Here, we propose to use ft1, cen, and int-m/dub1 mutants to dissect the molecular network underlying inflorescence meristem determinacy and identity transitions. Specifically, we will (i) identify IM and SM/FM-specific changes in transcriptional networks downstream of FT1/CEN and INT-M using laser capture microdissection (LCM) and RNA-sequencing (LCM-RNA-seq) followed by functional analyses of candidate genes and (ii) decipher the link between IM and SM determinacy and hormone homeostasis and response using hormone reporter lines and measurements of hormone level changes. The ultimate goal is to identify molecular networks that specifically control the fate of the different barley meristems, IM and SM/FM. By integrating information from the consortium partners on the regulation of different stem cell systems in maize, barley and Brachypodium we will be able to develop a common framework on the molecular control of cereal stem cell systems and their variation between different meristems and species.