The CsUGT87A1 gene enhances drought stress tolerance in tea plants by modulating IAA homeostasis

Drought is a major abiotic stressor that threatens global agriculture. Thus, it is imperative to unravel the molecular processes that underlie plant drought resistance. UDP-glycosyltransferases (UGTs), also known as family 1 glycosyltransferases, are essential for plant growth and development, stress responses, and other physiological processes. The precise physiological functions of numerous UGT members in response to plant abiotic stressors remain largely unclear, despite their significance. A novel glycosyltransferase (CsUGT87A1) has been discovered in tea plants, a significant economic crop, according to this study. This gene's expression is significantly upregulated under drought stress conditions. CsUGT87A1 is predominantly expressed in the roots, and its protein is located in the cell nucleus. Enzyme activity tests demonstrated that the recombinant CsUGT87A1 (rCsUGT87A1) showed catalytic activity when indole-3-acetic acid (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. Furthermore, there was a notable rise in IAA in Arabidopsis when CsUGT87A1 was expressed heterologously. Increases in seed germination rate, root length, chlorophyll and photosynthetic parameters, proline, and antioxidant activities, as well as a drop in ROS and MDA levels as compared to EV lines, all demonstrated a significant improvement in drought resistance in the transgenic Arabidopsis. 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.