WHIRLY1 Regulates HSP21.5A Expression to Promote Thermotolerance in Tomato

摘要

Heat stress poses a major threat to plant productivity and crop yields. The induction of heat shock proteins (HSPs) by heat shock factors is a principal defense response of plants exposed to heat stress. In this study, we identified and analyzed the heat stress-induced Whirly1 (SIWHY1) gene in tomato (Solanum lycopersicum). We generated various SIWHY1-overexpressing (OE) and SIWHY1-RNA interference (RNAi) lines to investigate the role of WHIRLY1 in thermotolerance. Compared with the wild type (WT), the OE lines showed less wilting, as reflected by their increased membrane stability and soluble sugar content and reduced reactive oxygen species (ROS) accumulation under heat stress. By contrast, RNAi lines with inhibited SIWHY1 expression showed the opposite phenotype and corresponding physiological indices under heat stress. The heat-induced gene SIHSP21.5A, encoding an endoplasmic reticulum-localized HSP, was upregulated in the OE lines and downregulated in the RNAi lines compared with the WT. RNAi-mediated inhibition of SIHSP21.5A expression also resulted in reduced membrane stability and soluble sugar content and increased ROS accumulation under heat stress compared with the WT. SIWHY1 binds to the elicitor response element-like element in the promoter of SIHSP21.5A to activate its transcription. These findings suggest that SIWHY1 promotes thermotolerance in tomato by regulating SIH5P21.5A expression.