PCP-bε is a novel positive regulator of pollen germination in Arabidopsis thaliana

small cysteine-rich peptides play essential roles in different stages of the plant reproductive process. Pollen germination is a prerequisite for double fertilization and is directly related to seed formation and crop yield. However, the small cysteine-rich peptides that are involved in pollen germination remain to be identified. In this study, identification and phylogenetic analysis of PCP-Bε genes in sequenced Brassicaceae show that pollen coat protein B-class protein PCP-Bε gene is widespread in Arabidopsis and its high relatives, but lost in some Brassica species. Expression analyses display that AtPCP-Bε gene is expressed in Arabidopsis pollen. Arabidopsis PCP-Bε knockout mutants are generated by CRISPR/Cas9, Phenotypic analyses show that the absence of AtPCP-Bε obviously impairs in vitro pollen germination, but has no influence on pollen tube growth, which demonstrates that AtPCP-Bε is a novel positive regulator of pollen germination. It is speculated that AtPCP-Bε should interact with the receptor from pollen to perform its function. These findings are useful for further analysis on the molecular mechanism of pollen germination.