Photosynthesis Response and Transcriptional Analysis: Dissecting the Role of SlHB8 in Regulating Drought Resistance in Tomato Plants

Deciphering drought resistance in crops is crucial for enhancing water productivity. Previous studies have highlighted the significant role of the transcription factor SlHB8 in regulating developmental processes in tomato plants but its involvement in drought resistance remains unclear. Here, gene overexpression (SlHB8-OE) and gene knockout (slhb8) tomato plants were utilized to study the role of SlHB8 in regulating drought resistance. Our findings showed that slhb8 plants exhibited a robust resistant phenotype under drought stress conditions. The stomata of slhb8 tomato leaves displayed significant closure, effectively mitigating the adverse effects of drought stress on photosynthetic efficiency. The slhb8 plants exhibited a decrease in oxidative damage and a substantial increase in antioxidant enzyme activity. Moreover, slhb8 effectively alleviated the degree of photoinhibition and chloroplast damage caused by drought stress. SlHB8 regulates the expression of numerous genes related to photosynthesis (such as SlPSAN, SlPSAL, SlPSBP, and SlTIC62) and stress signal transduction (such as SlCIPK25, SlABA4, and SlJA2) in response to drought stress. Additionally, slhb8 plants exhibited enhanced water absorption capacity and upregulated expression of several aquaporin genes including SlPIP1;3, SlPIP2;6, SlTIP3;1, SlNIP1;2, and SlXIP1;1. Collectively, our findings suggest that SlHB8 plays a negative regulatory role in the drought resistance of tomato plants.