Molecular mechanisms of drought tolerance in Lespedeza davurica: Identification and functional characterization of a novel ALDH family gene (LdALDH2-19) in drought stress adaptation.

Drought stress is a significant environmental challenge impacting plant growth and productivity. This study investigates the drought tolerance mechanisms of Lespedeza davurica, a drought-tolerant legume, by analyzing root physiological responses and conducting RNA-Seq analysis under controlled drought conditions. Plants were subjected to drought stress for ten days and then rewatered to assess recovery. We measured key physiological parameters such as proline accumulation, antioxidative enzymes activity, and electrolyte leakage. RNA-Seq identified 6482 differentially expressed genes (DEGs) under drought stress, with upregulated genes primarily involved in antioxidant processes (e.g., glutathione and ascorbate metabolism) and downregulated genes were linked to carbon metabolism. Following rewatering, gene expression was restored, with significant upregulation in nitrogen metabolism and amino sugar metabolism pathways, reflecting enhanced energy metabolism and accelerated recovery. Weighted Gene Co-expression Network Analysis (WGCNA) identified 50 core drought-tolerance genes, with LdALDH2-19 selected for functional analysis. Overexpression of LdALDH2-19 in hairy roots (OE-LdALDH2-19) significantly alleviated oxidative damage under osmotic stress, as indicated by reduced MDA levels accompanied by increased antioxidant enzyme activity compared to the control (EV). These findings suggest that LdALDH2-19 plays a critical role in drought tolerance by mitigating oxidative stress and contributing ROS homeostasis, offering insights for improving drought resistance in leguminous crop breeding.