OsNAC45 plays complex roles by mediating POD activity and the expression of development-related genes under various abiotic stresses in rice root

Abstract

OsNAC45 belongs to the NAC family of (for NAM/ATAF1/2/CUC2) transcription factors, which play an important role in plant development and abiotic stress responses. Transgenic rice plants overexpressing OsNAC45 have exhibited improved tolerance to salt and drought stress. This study aimed to investigate the mechanism underlying the effects of OsNAC45 on root development under abiotic stress in rice Zhonghua11 (ZH11) (Oryza sativa L.). The OsNAC45 GUS expression was strong in roots of the adult stage, weak in the seedling stage, and induced by low-temperature stress in the seedling stage. Under NaCl and low temperature stress, the OsNAC45 overexpression (OE) lines exhibited maintenance of root structure and normal growth of the seedling root, but the RNAi lines of OsNAC45 were more sensitive. The roots of the OE lines accumulated less superoxide anion under low temperature stress and more hydrogen peroxide under normal conditions than WT. After NaCl treatment, the Peroxidase (POD) assay showed POD activity of the roots in OE lines were elevated, but were decreased in RNAi lines and WT; additionally, the increment of lignin content in OE lines was significantly higher than RNAi lines and WT in roots. Furthermore, expression levels of some rice root development-related genes were altered in the transgenic plants. Under cold and salt stresses, expression of NCED4, a key enzyme in abscisic acid synthesis, was decreased in OE lines and raised in RNAi lines compared to WT. The data suggests that OsNAC45 may participate in the response of cold/salt stresses by lessening the accumulation of reactive oxygen species and increasing lignin in rice roots thus alleviating the restraint to the growth of seedling root. Overexpression of OsNAC45 weakened the high temperature tolerance; however, inhibiting its expression could improve the tolerance. Together, these results indicate that OsNAC45 plays an important role in the coordination, development, and response of rice plants under abiotic stresses.