Receptor-like Kinase CrRLK1-L Subfamily:Novel Motifs in Extracellular Domain and Biological Functions in Plants

CrRLK1-L receptor-like kinases(RLKs) possess novel motifs with unknown functions in the extracellular domain and the typical Ser/Thr kinase domain in the intracellular region.CrRLK1-L subfamily spread broadly in angiosperm,however,no homologs of CrRLK1-L proteins exist in animals and microorganisms.CrRLK1-L RLKs express extensively in most of tissues,and mainly involve in signal exchanging between male and female gametophytes,the sensing of cell-wall-integrality and cell elongation control of the vegetative organs,and also in the response of cell to diverse biotic stress,etc.CrRLK1-L RLKs commonly localize on plasm-membrane,and their kinase activity is essential for their biological functions.Therefore,CrRLK1-L RLKs can function as cell surface sensor for extracellular signal and initiate a signal transduction that largely independent of the known phytohormone signaling pathways.Detailed study of CrRLK1-L RLKs gene functions will be helpful for our understanding the molecular mechanisms in the special biological processes in plant,especially in sexual reproduction in that optimal utilization will benefit the agriculture production in future.