A major latex protein, TaSTP, coordinates sugar-antioxidant synergy to enhance drought tolerance in wheat

Drought is a major environmental factor that hinders plant growth and development, thereby threatening crop yields. The major latex protein (MLP) plays an important role in modulating plant stress responses and development. However, the roles and molecular mechanism of MLP in drought stress response remain unclear. Here, we identified a wheat MLP member TaSTP, and its overexpression in wheat exhibited enhanced drought tolerance, whereas silencing TaSTP increased drought sensitivity. Additionally, TaSTP-overexpressing lines exhibited higher yields under drought conditions. Transcriptome sequencing analysis revealed that TaSTP significantly upregulates genes involved in the osmotic regulatory and sugar metabolism pathway, thereby increasing antioxidant capacity and sugar content. Moreover, we also found that exogenous application of glucose and sucrose effectively enhanced drought tolerance in wheat. A 172 bp fragment insertion in the TaSTP-2A promoter created two allelic variants, Hap-2A-I and Hap-2A-II, which differ in transcriptional levels and drought tolerance. This insertion allows binding of the zinc finger transcription factor TaZAT5L, strongly repressing TaSTP expression in Hap-2A-I, but not in Hap-2A-II. The superior allele Hap-2A-II has been preferentially selected during wheat breeding in China. Collectively, our results demonstrate that TaSTP enhances drought tolerance by promoting reactive oxygen species (ROS) scavenging and sugar accumulation. These findings provide novel insights into the roles and molecular mechanisms of TaSTP in plants.