SlbHLH053 and AtMSRB5 synergistically enhance salt tolerance in transgenic tomatoes

• Overexpression of AtMSRB5 reduces sodium toxicity and promotes potassium uptake, maintaining cellular functionality during salt stress. • Overexpression of SlbHLH053 enhances iron uptake and accumulation, critical for photosynthesis and cellular integrity under saline conditions. • Co-expressing SlbHLH053 and AtMSRB5 boosts salt tolerance in transgenic tomatoes by enhancing ion balance and antioxidant activity, offering a strategy for resilient crops in saline conditions. Salt stress significantly affects crop yield. In this study, we found that co-expressing SlbHLH053 and AtMSRB5 can enhance salt tolerance in tomato plants. Our results indicated that the simultaneous expression of these genes improved tolerance to higher salt concentrations in transgenic tomatoes. We showed that SlbHLH053 is localized in the nucleus and can form homodimers, suggesting its role as a transcription factor. Furthermore, SlbHLH053 was able to bind to E-box elements and transactivate the SlCI7 promoter in vitro . Additionally, SlbHLH053 was found to have a role in salt and iron deficiency stress response, and in regulating iron homeostasis and antioxidant pathways. AtMSRB5 was verified to be important in maintaining ion balance and enhancing salt tolerance in transgenic tomato plants. The combination of both SlbHLH053 and AtMSRB5 led to an even greater tolerance to salt stress than either gene alone. The transgenic plants also exhibited improved ion homeostasis, with reduced sodium and elevated potassium levels under salt stress. The overexpression of SlbHLH053 and AtMSRB5 led to higher iron content and increased activity of antioxidant enzymes, such as ascorbate peroxidase and catalase, which are crucial for combating oxidative stress. These results also indicated that SlbHLH053 and AtMSRB5 mediate different antioxidant pathways to contribute to enhanced salt tolerance in transgenic tomato plants. In conclusion, the co-expression of the two genes in this study demonstrates a multifaceted approach to enhancing salt stress tolerance that may provide significant advantages for developing resilient crops in challenging environments.