The Csugt87a1 Enhances Drought Stress Tolerance in Tea Plants by Modulating Iaa Homeostasis

Abstract

Drought is a major abiotic stress that poses a significant threat to global agriculture, highlighting the urgent need to unravel the molecular mechanisms underlying plant drought tolerance. Family 1 glycosyltransferases, also known as UDP-glycosyltransferases (UGTs), play key roles in plant growth and development, stress responses, and other physiological processes. However, the physiological roles of most members of UGTs in response to plant abiotic stresses remain unknown. We have identified a novel glycosyltransferase CsUGT87A1 in tea plants, an important economic crop, whose expression is strongly induced by drought stress. CsUGT87A1 is preferentially expressed in roots and its protein localizes in the cell nucleus. Enzyme activity assays revealed that rCsUGT87A1 exhibited catalytic activity when IAA was used as a substrate in vitro. Downregulating the CsUGT87A1 gene, using the anti-sense oligonucleotide (ASO) gene silencing technology, significantly decreased drought resistance and lowered IAA levels in tea plant seedlings. Additionally, heterologous expression of CsUGT87A1 in Arabidopsis led to a significant increase in IAA. Drought resistance in the transgenic Arabidopsis was also enhanced significantly as indicated by the increased seed germination rate, root length, chlorophyll and photosynthetic parameters, proline, and anti-oxidant activities, while ROS and MDA contents decreased as compared to EV lines. Collectively, our findings indicate that CsUGT87A1 may act as a positive regulator of IAA biosynthesis in response to drought stress in plants. Our results enrich the roles of auxin glycosyltransferases in drought tolerance of plants and laid a foundation for cultivating transgenic crops with higher resistance to water stress.

Keywords: Glycosyltransferases, CsUGT87A1, Camellia sinensis, Drought stress