CLE peptide hormones and their role in stem cell regulations in Arabidopsis
Chun-Ming Liu

Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China cmliu@ibcas.ac.cn.

Abstract
Peptides have long been recognized as hormones in animals, which act as intercellular communication signals in endocrinal and neural systems. They are usually produced as pre-proproteins, which are cleaved and sometimes modified to generate small functional peptides. Since the first peptide hormone, systemin, was discovered two decades ago in plants, many small peptides have been identified in different species, which play crucial roles in development and defense responses. As the funding member of CLE peptides, CLV3 acts as a secreted 12 to 13 AA peptide. CLV3 interacts with CLV1/CLV2/SOL2 receptor kinases in the neighboring cells to promote the differentiation of stem cells in shoot apical meristems (SAM), while WUS transcription factor restricts the differentiation of the stem cells. They two form a feedback regulation loop to maintain fixed number of stem cells in SAM. In the last few years, we have been studying CLV3 and CLE19 peptides in Arabidopsis, to understand their roles in stem cell regulation in shoot and root meristems, and to elucidate how peptide specificities are embedded in amino acid sequences, and to develop new technologies for studying peptide ligands. I will give an overview on what have achieved in the past years.