Genome-wide investigation of the PYL genes in Acer palmatum and their role in freezing tolerance

As the direct recipients of plant abscisic acid (ABA), pyrabactin resistance/pyrabactin resistance-like/regulatory component of ABA receptor proteins (PYR/PYL/RCAR; hereinafter called PYLs) play pivotal roles in plant coercive responses. However, the PYL genes in Acer palmatum have yet to be investigated. In this study, using a genome search method, we identified 14 A. palmatum PYL genes (ApPYLs) and clustered them into three clades based on the phylogenetic, gene structure, and conserved motif analyses. The ApPYLs were dispersed on eight chromosomes of A. palmatum; cis-acting element analysis indicated that the ApPYLs were involved in biological processes, including resistance, hormone regulation, and growth. Gene expression profiling of cold-treated A. palmatum plants revealed that ApPYL1 and ApPYL2 may be related to cold stress response. ApPYL1 and ApPYL2 interacted directly with ApMYB44, and the ApPYL1, ApPYL2, and ApMYB44 genes were found to enhance freezing tolerance in Arabidopsis. These findings illustrate that ApPYL1 and ApPYL2 respond to the cold signalling pathway by interacting with ApMYB44 and provide a reference for improving cold resistance of plants.