SlFBX38, an F-Box Protein, Enhances Thermotolerance in Tomato

Heat stress, intensified by global warming, poses a great threat to plant growth and crop production. However, the molecular mechanisms underlying heat stress response (HSR) remain largely unclear. In this study, we identified and characterized SlFBX38, an F-box gene in tomato. SlFBX38 was predominantly expressed in leaves and fruits, and its expression levels were induced by heat stress and various phytohormones, including ABA, JA and SA. Subcellular location analysis revealed that SlFBX38 resides in both the nucleus and cytoplasm in N. benthamiana leaf cells, but it displays no transcriptional activity. Overexpression of SlFBX38 (OE) lines conferred enhanced heat stress tolerance, as evidenced by improved photosynthetic efficiency, elevated accumulation of ascorbic acid (AsA), stronger protective enzyme activities, and upregulation of HSR-related genes in SlFBX38-OE lines under heat stress condition. To identify potential interacting proteins, yeast two-hybrid (Y2H) library screening and further Y2H verification indicate that SlFBX38 may interact with SlbHLH058. Collectively, these findings establish SlFBX38 as a positive regulator of thermotolerance in tomato and provide a basis for further mechanistic studies of its role in HSR.