Overexpression of Rice Cullin Gene Confers Salt Tolerance in the Salt-Sensitive Arabidopsis Mutant Lacking cul3a

By genome-wide association study (GWAS), candidate loci associated with salt tolerance were identified in Thai rice population. The putative causative genes yielded from GWAS that have Arabidopsis homologs were selected for functional characterization. We found that Arabidopsis mutant of Cullin3a (cul3a) was more sensitive to salt stress than wild-type (WT). CUL3a is a member of ubiquitin E3 ligases, which regulate protein stability. However, the function of CUL3a in salt stress responses is not known. In this study, we overexpressed a rice cullin3 gene in the Arabidopsis WT and the Arabidopsis mutant of cul3a. All overexpressing lines exhibited higher germination rates than the cul3a mutant under salt stress. When 7-day old seedlings were treated with 120 mM NaCl for 5 days, all overexpressing lines exhibited higher growth measured by fresh weights and dry weights than the mutant. In addition, when compared with the cul3a mutant, they showed higher carotenoid contents under salt stress. Taken together, the rice cullin3 gene can revert the salt-sensitive phenotype of the Arabiopsis cul3a mutant under salt stress suggesting the function of rice cullin3 in the mechanism of salt stress response in rice.