Investigation of the potential regulation of the UDP-glycosyltransferase genes on rice grain size and abiotic stress response

Uridine diphosphate (UDP) glycosyltransferases (UGTs) are widely involved in various metabolic processes. In the present study, we performed a genome-wide survey and identified 199 Oryza sativa UGT genes (OsUGTs), which were classified into 17 groups. We showed that tandem duplication played a major role in the expansion of the OsUGT family, which experienced purifying selection during the evolution process. 163 OsUGTs were expressed in at least one of the six tested tissues, and were clustered into three groups according to their tissue expression profiles. By using the RFGB database, we identified different haplotypes of seven OsUGTs that were highly expressed in seeds, and showed significant differences in grain size among different haplotypes. Moreover, our results also uncovered differential responses of OsUGTs expression to abiotic stresses and hormone treatments, including drought, salt, cold, heat, ABA, JA and AUXIN. By using quantitative real-time PCR, we further confirmed the differential expression of nine selected OsUGTs under ABA, JA, salt, drought and cold treatments, among which OsUGT5 and OsUGT182 were induced by all these five treatments. Our results provide insight into the role of several UGT genes for physiological responses, which will facilitate to investigate their function in regulating rice development and abiotic stress responses.