Genome-Wide Identification and Analysis of the JAZ Gene Family in Rapeseed Reveal JAZ2 and JAZ3 Roles in Drought and Salt Stress Tolerance

The phytohormone jasmonic acid (JA) plays an important role in diverse physiological processes. The jasmonate ZIM-domain (JAZ) proteins act as repressors of JA signaling and have been extensively studied in Arabidopsis thaliana. However, little is known about their function in the oil crop rapeseed (Brassica napus L.). Here, a total of ten BnaJAZs were cloned, whose encoded proteins harbor complete TIFY and Jas domains. Phylogenetic analysis showed that the BnaJAZs from representative plant species are clustered into five groups. Subcellular localization assay showed that BnaJAZs can function in nuclei and/or the cytoplasm. RT-qPCR results demonstrated that BnaJAZs displayed differential expression patterns and most showed induction by JA and significant changes to ABA (abscisic acid), salt, and dehydration treatments. Further, we found that overexpression (OE) of BnaJAZ2 improved drought tolerance, while RNAi silencing of it decreased drought tolerance. Moreover, overexpression of BnaJAZ3 enhanced the salinity sensitivity. A further RNA-seq analysis uncovered the differentially expressed genes and relevant pathways implicated in the biosynthesis of osmoprotectants and stress hormones as well as ROS scavenging were mostly up- and down-regulated in BnaJAZ2-OE and BnaJAZ3-OE lines, respectively, compared with GFP-OE. In summary, this study provides a basis for further exploration of BnaJAZ functions in abiotic stress response and tolerance for the goal of developing stress-tolerant cultivars.