Identification and expression analysis of <i>PUB</i> genes in tea plant exposed to anthracnose pathogen and drought stresses

The plant U-box (PUB) gene family, one of the major ubiquitin ligase families in plants, plays important roles in multiple cellular processes including environmental stress responses and resistance. The function of U-box genes has been well characterized in <i>Arabidopsis</i> and other plants. However, little is known about the tea plant (<i>Camellia sinensis</i>) <i>PUB</i> genes. Here, 89 U-box proteins were identified from the chromosome-scale referenced genome of tea plant. According to the domain organization and phylogenetic analysis, the tea plant PUB family were classified into ten classes, named Class I to X, respectively. Using previously released stress-related RNA-seq data in tea plant, we identified 34 stress-inducible <i>CsPUB</i> genes. Specifically, eight <i>CsPUB</i> genes were expressed differentially under both anthracnose pathogen and drought stresses. Moreover, six of the eight <i>CsPUB</i>s were upregulated in response to these two stresses. Expression profiling performed by qRT-PCR was consistent with the RNA-seq analysis, and stress-related cis-acting elements were identified in the promoter regions of the six upregulated <i>CsPUB</i> genes. These results strongly implied the putative functions of U-box ligase genes in response to biotic and abiotic stresses in tea plant.