Rice glycosyltransferase gene UGT2 functions in salt stress tolerance under the regulation of bZIP23 transcription factor.

KEY MESSAGE: Rice glycosyltransferase gene UGT2 was identified to play a crucial role in salt tolerance. The transcription factor OsbZIP23 was demonstrated to regulate the UGT2 expression under stress conditions. UDP-glycosyltransferases (UGTs) play key roles in modulating plant responses to environmental challenges. In this study, we characterized a novel glycosyltransferase, UGT2, which plays an important role in salt stress responses in rice (Oryza sativa L). We found that seedlings overexpressing UGT2 exhibited better growth than wild type in shoot and root under hydroponic culture with salt stress treatments, while ugt2ko mutant lines suffered much more growth inhibition. When the soil-grown UGT2 transgenic plants were subjected to salt stress, we also found that ugt2ko mutant lines were severely withered and most of them died, while the overexpression lines grew well and had higher survival rate. Compared with wild-type plants, UGT2 overexpression greatly increased the expression levels of the reactive oxygen species scavenging genes and stress-responsive genes. Furthermore, the upstream regulatory mechanism of the UGT2 gene was identified and we found that a bZIP transcription factor, OsbZIP23, can bind to the UGT2 promoter and enhance the UGT2 transcription levels. This work reveals that OsbZIP23-UGT2 module may play a major role in regulating the salt stress tolerance in rice.