Genome-Wide Analysis of the JAZ Family in Brassica rapa and the Roles of BrJAZ1a and 6b in Response to Stresses

Jasmonate-ZIM domain (JAZ) proteins act as repressors in the jasmonic acid (JA) signaling pathway and also function as plant-specific proteins participating in plant growth and development, stress response, and defense. In our study, a total of 25 <i>JAZ</i> genes were identified in <i>B. rapa</i> based on their conserved domains. First, the primary characteristics were surveyed, including the lengths of the CDS and proteins, molecular weights, and isoelectric points. Next, a phylogenetic tree of JAZ proteins among <i>B. rapa</i>, <i>A. thaliana</i>, <i>O. sativa</i>, <i>B. oleracea</i>, and <i>B. napus</i> was constructed, which revealed that these proteins cluster into four groups based on sequence homology rather than by species. Synteny analysis of <i>JAZ</i> genes among these species demonstrated that the highest number of collinear pairs was found between <i>B. rapa</i> and <i>B. napus</i>. Most <i>BrJAZ</i> genes were highly expressed in root, stem, and leaf. Moreover, the expression levels of <i>BrJAZ1a</i> and <i>BrJAZ6b</i> were induced by drought, high salt, black rot, and MeJA. Over-expressed these genes in <i>A. thaliana</i> lines enhanced their tolerance to drought and high salt stress, which was associated with higher enzymatic activities of SOD and POD. Both <i>BrJAZ1a</i>-GFP and <i>BrJAZ6b</i>-GFP were localized in the nucleus.