Abstract
The shoot apical meristem (SAM) is the fundamental structure that is located at the growing tip and gives rise to all aerial parts of plant tissues and organs. In Arabidopsis thaliana, the CLAVATA3 (CLV3) pathway regulates the stem cell pool in the SAM, in which a small peptide ligand derived from CLV3 is perceived by two major receptor complexes, CLV1 and CLV2- CORYNE (CRN) /SUPPRESSOR OF LLP1 2 (SOL2), to restrict WUSCHEL (WUS ) expression. In this study, we utilized the functional, synthetic CLV3 peptide (MCLV3) to isolate CLV3-insensitive mutant and revealed that a receptor-like kinase, RECEPTOR-LIKE PROTEIN KINASE 2 (RPK2) is another key regulator of meristem maintenance. Mutations in the RPK2 result in stem cell expansion and increased the number of floral organs, as seen in the other clv mutants. These phenotypes are additive with both clv1 and clv2. Moreover, our biochemical analyses using Nicotiana benthamiana revealed that RPK2 does not associate with CLV1 or CLV2. These genetic and biochemical findings suggest that three major receptor complexes are likely to mediate three signalling pathways to regulate the SAM homeostasis.
