StTCTP Positively Regulates StSN2 to Enhance Drought Stress Tolerance in Potato by Scavenging Reactive Oxygen Species.

Drought is a negative agronomic effect that can lead to an increase in reactive oxygen species (ROS) levels. Excessive drought can severely alter cell membrane fluidity and permeability, significantly reducing cell viability. The Gibberellic acid-stimulated Arabidopsis (Snakin/GASA) gene family has an important role as antioxidants in inhibiting the accumulation of ROS and improving crop drought resistance. However, the regulatory mechanism of potato StSnakin-2 (StSN2) in response to drought, along with how StSN2 expression is regulated, is not well understood. In this study, we found that StSN2 was induced by drought. Overexpression of StSN2 significantly increased drought tolerance, whereas silencing StSN2 increased sensitivity to drought. Overexpression of StSN2 resulted in higher antioxidant enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activity, and lowered hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) accumulation during drought stress. Also, overexpression of StSN2 increased the relative water content (RWC) of leaves and reduced the water loss in leaves. We screened the upstream regulatory protein translation-controlled tumor protein (StTCTP) of StSN2 through DNA pull-down combined with mass spectrometry. Yeast one-hybrid (YIH), electrophoretic mobility shift assay (EMSA), and luciferase reporting assay (LUC) indicated that StTCTP binds the StSN2 promoter. Like StSN2, StTCTP was highly expressed in response to drought. Overexpression of StTCTP increased the photosynthetic rate and CAT enzyme activity, and lowered H₂O₂ and MDA accumulation during drought. Meanwhile, overexpression of StTCTP increased leaf RWC and reduced water loss. Our research strongly suggested that StSN2 effectively cleared ROS and significantly boosted the drought resistance of potatoes. Furthermore, as a transcriptional activator of StSN2, StTCTP, much like StSN2, also enhanced the potato's drought tolerance. The results provided a foundation for the further study of StSN2 regulatory mechanisms under drought stress.