SlZAT5 and SlJIG Regulate Drought Tolerance in Tomato by Modulating ABA Homoeostasis

Vegetable cultivation is heavily reliant on an ample water supply, with water deficiency limiting seedling growth and final yield. The phytohormone abscisic acid (ABA) is recognised for its role in drought tolerance by promoting stomatal closure to reduce water loss. This study identifies that drought treatment upregulated the C2H2-type zinc finger protein SlZAT5 and the bHLH transcription factor SlJIG, leading to enhanced ABA accumulation and drought tolerance. Immunoprecipitation-Mass Spectrometry (IP-MS) analysis revealed the interaction between SlZAT5 and SlJIG. Both transcription factors can bind to the promoter of the ABA catabolism gene SlCYP707A3. However, SlJIG alone was insufficient for transcriptional repression of SlCYP707A3, which instead required SlZAT5's transrepression activity. Additionally, SlJIG strengthened the inhibitory effect of SlZAT5 on SlCYP707A3. Overexpression of either SlZAT5 or SlJIG improved tomato drought tolerance, whereas knockout of either gene reduced drought tolerance, with the double mutant exhibiting a further decline. These findings elucidate the role of the SlZAT5-SlJIG module in regulating tomato drought responses via ABA homoeostasis.