Mitogen-Activated Protein Kinase regulated by the CLAVATA receptors contributes to the shoot apical meristem homeostasis

Abstract

In Arabidopsis, the CLAVATA (CLV) pathway operates in the regulation of the size of the stem cell population in the shoot apical meristem (SAM). CLV3 functions as a small peptide ligand to negatively regulate the expression of WUSCHEL (WUS) transcription factor through three major receptor kinase complexes of CLV1, CLV2-SUPPRESSOR OF LLP1-2 (SOL2)/CORYNE (CRN) and recently identified RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2)/TOADSTOOL 2 (TOAD2). In this study, we investigated the contribution of phospho-signalling, regulated by these kinase complexes, to the CLV pathway. We detected CLV3-triggered CLV1 phosphorylation, which are also conditioned by the rest of the CLV receptors, presumably by their direct association. Our comprehensive analysis of the activities of the respective CLV receptors on MAPK suggested that the precise balanced regulation of MAPK activity by the CLV receptors is likely to be a key for the SAM homeostasis.