Genome-Wide Identification and Characterization of the JAZ Gene Family in Rubber Tree (Hevea brasiliensis)

Jasmonate signaling plays a vital role in the regulation of secondary laticifer differentiation and natural rubber biosynthesis in Hevea brasiliensis. Jasmonate ZIM-domain (JAZ) proteins are the master regulators of jasmonate signaling. Although several JAZs have been reported in the laticifer cells of H. brasiliensis, the genome-wide screening of HbJAZ members has not yet been explored. In the present study, 18 HbJAZs were identified based on the recent H. brasiliensis genome. Phylogenetic construction revealed that the HbJAZs were clustered into five subgroups and that members within the same subgroup shared highly conserved gene structures and protein motifs. Cis-element analysis of HbJAZ promoters suggested the presence of hormone, stress and development-related cis-elements. HbJAZ1.0, HbJAZ2.0, and HbJAZ5.0 interacted with CORONATINE INSENSITIVE1 (COI1) in the presence of coronatine (COR, a JA mimic). HbJAZ1.0, HbJAZ2.0, HbJAZ5.0, and HbJAZ12.0 could also interact with each other. Of the 18 HbJAZs, transcripts of 15 HbJAZs were present in the vascular cambium region except for that of HbJAZ7.0, HbJAZ8.0d, and HbJAZ13.0. Fourteen of the 15 HbJAZs were significantly up-regulated upon COR treatment. The transcripts of three genes that were absent from vascular cambium region were also absent from the latex. Among the 15 HbJAZs in the latex, the expression patterns of 13 HbJAZs were different between the tapping and ethrel treatments. Eight of the 14 COR-up-regulated HbJAZs in the vascular cambium region were also activated by tapping in latex. Of the eight tapping-activated HbJAZs, 5 HbJAZs were repressed by ethrel application. Based on the computational analyses and gene expression patterns described in this study, the HbJAZ5.0 and HbJAZ10.0b may be associated with laticifer differentiation while the HbJAZ8.0b is a negative regulator for natural rubber biosynthesis in H. brasiliensis.