High-temperature stress severely limits the growth, development, and productivity of tomatoes. Understanding the molecular mechanisms underlying its thermotolerance is crucial for breeding heat-resistant varieties. This study employed a stepwise experimental strategy to systematically elucidate the role of the chlorophyll a/b-binding protein SlCAB3 in tomato thermotolerance. First, a high-temperature responsive transcription factor, SlDREBA4, previously identified in our lab, was used in a yeast two-hybrid screen to identify potential interacting proteins, including SlCAB3. The interaction between SlDREBA4 and SlCAB3 was further validated using tobacco in vivo luciferase complementation imaging (LCI) and in vitro pull-down assays. Subsequently, the expression patterns of SlCAB3 under heat stress were analyzed, and its biological function was further evaluated through overexpression, gene silencing, and knockout experiments. Additionally, reactive oxygen species (ROS) accumulation, antioxidant enzyme activities, chlorophyll content, and the expression of stress-responsive genes were measured to comprehensively assess their physiological and molecular regulatory roles. The results indicate that SlCAB3 encodes a typical chlorophyll a/b-binding protein and is rapidly induced by heat stress. Overexpression of SlCAB3 significantly enhances plant thermotolerance, evidenced by reduced heat damage, increased chlorophyll content, decreased ROS accumulation, elevated antioxidant enzyme activities, and upregulation of antioxidant-related genes. Conversely, silencing SlCAB3 produces opposite effects. Moreover, co-expression of SlCAB3 with SlDREBA4 further improves thermotolerance, accompanied by enhanced expression of heat shock protein-related and antioxidant-related genes. In conclusion, SlCAB3 is a positive regulator of tomato thermotolerance, and the interaction module formed with SlDREBA4 may collectively enhance heat resistance by strengthening antioxidant defense and heat stress response mechanisms.

The homeodomain–leucine zipper (HD-zip) gene family plays a crucial role in plant development and stress responses. However, systematic identification studies of this gene family in eggplant are still lacking. In this study, we systematically identified 44 HD-zip genes in the eggplant genome database using bioinformatics methods and analyzed their expression levels under light and multiple hormones by RT-qPCR. The results show that members of the SmHD-zip gene family were classified into four groups (HD-zip I, II, III, and IV) based on the phylogenetic relationship. Cis-acting elements related to plant development, hormones, and stress were identified in the promoter regions of the SmHD-zip gene family. Furthermore, the expression of the SmHDZ2 gene was upregulated during the fruit development stage, while nine SmHD-zip genes exhibited downregulated expression patterns. Notably, some SmHD-zip genes were identified as key regulators of eggplant responses to light and multiple hormone signals. Overall, these findings not only provide valuable insights into the evolutionary and functional characteristics of eggplant HD-Zips but also suggest that HD-zip genes likely play a significant role in regulating fruit development and ripening by integrating light and multiple hormone signaling pathways. Therefore, this study laid the foundation for further research on eggplant quality.