Genome-wide identification and functional characterization of drought-responsive U-box E3 ubiquitin ligase genes in...

As a family of E3 ubiquitin ligases, plant U-box (PUB) proteins participate in various biological processes, but research on their molecular characteristics and functional divergence in Rosa chinensis remains limited. Herein, we identified a total of 69 RcPUB genes from the Rosa chinensis genome, which displayed a non-uniform distribution on the chromosomes, with 19 members specifically clustered on chromosome 2. A phylogenetic analysis indicated that RcPUB proteins can be divided into five subfamilies (Clade I to V), each harboring a unique conserved domain. Cis-Acting element analysis demonstrated that the promoters of RcPUB genes contain abundant elements associated with various plant hormones. Combined RNA-seq and WGCNA analysis screened out two important drought stress-responsive genes (RcPUB4 and RcPUB14), and the proteins encoded by these genes are both localized in the nucleus. VIGS-induced silencing of RcPUB4 conferred drought tolerance and significantly altered the expression of ABA signaling-related genes. Besides, protein-protein interaction prediction and yeast two-hybrid assays revealed that RcPUB4 targets two ABA receptors (RcPYL4 and RcPYL9),supporting the notion that RcPUB4 may regulate the stability of these ABA receptors, thus influencing the transduction efficiency of the ABA signaling and ultimately mediating drought tolerance in Rosa chinensis. Altogether, this study yields a foundational understanding of the Rosa chinensis RcPUB gene family and provides a valuable reference for in-depth exploration of their molecular mechanisms in drought stress adaptation.