Genome-wide identification and comparative analysis of the PYL gene family in eight Rosaceae species and expression analysis of seeds germination in pear.

Abscisic acid (ABA) is a phytohormone that plays important roles in the regulation of plant growth, seed germination, and stress responses. The pyrabactin resistance 1-like (PYR/PYL) protein, an ABA receptor, was involved in the initial step in ABA signal transduction. However, the evolutionary history and characteristics of PYL genes expression remain unclear in Chinese white pear (Pyrus bretschneideri) or other Rosaceae species. In this study, 67 PYL genes were identified in eight Rosaceae species, and have been classified into three subgroups based on specific motifs and phylogenetic analysis. Intriguingly, we observed that whole-genome duplication (WGD) and dispersed duplication (DSD) have a major contribution to PYL family expansion. Purifying selection was the major force in PYL genes evolution. Expression analysis finds that PYL genes may function in multiple pear tissues. qRT-PCR validation of 11 PbrPYL genes indicates their roles in seed germination and abiotic stress responses. Our study provides a basis for further elucidation of the function of PYL genes and analysis of their expansion, evolution and expression patterns, which helps to understand the molecular mechanism of pear response to seed germination and seedling abiotic stress.