ABSTRACT: Spinach (Spinacia oleracea L.) is an economically important and globally consumed popular leafy vegetable that is heat-sensitive. Heat stress caused by global climate change is one of the primary deleterious elements limiting spinach production worldwide. Little work has been done to explore the heat-responsive mechanisms of spinach under high temperature-induced stress. In the present study, we used iTRAQ-based proteomic and transcriptomic approaches to investigate physiological, metabolic, and proteomic responses of spinach in response to day / night temperature of 35°C / 25°C compared to 20°C / 15°C for 4 days. A total of 3,543 differentially expressed genes (DEGs) were detected using transcriptome sequencing, of which 2,086 DEGs were downregulated and 1,457 were upregulated. The DEGs were mainly involved in superoxide dismutase activity, catalase, and peroxidase activity. A total of 3,246 differentially abundant proteins were detected using iTAQ-based quantitative proteomic approach, from which 567 differentially expressed proteins (DEPs) (277 upregulated and 290 downregulated) were identified. DEPs were mainly assigned to pathways related to metabolism, signal transduction, protein degradation, defense, and antioxidant. Four genes - superoxide dismutase (SOD, LOC110788339), catalase (CAT, LOC110790286), peroxidase (POD, LOC110775253), and heat shock protein (HSP, LOC110799288) - were validated using quantitative real-time PCR (qRT-PCR) to verify the proteomic and transcriptomic analyses, showing different transcriptional and translational expression levels. The findings of this study provide a fundamental understanding of the metabolic pathways and biological processes that control adaptation to heat stress in spinach, and provide novel insight into the development of heat-tolerant spinach.
