Genome-wide analysis of the SlEIN3/EIL gene family and the roles of SlEIL3 in enhancing salt tolerance in tomatoes

Ethylene Insensitive 3/Ethylene Insensitive 3-Like (EIN3/EILs) proteins serve as the central hub of ethylene signaling in plants, regulating diverse processes such as growth, development, and stress responses. However, the role of EILs in tomatoes under salt stress remains poorly understood. In this study, we identified nine SlEIL genes, which were classified into three subfamilies with high conservation within each subfamily. Analysis of cis-acting elements revealed that SlEIL genes contain numerous stress-responsive and hormone-responsive elements. Tissue-specific expression analysis showed that certain genes are highly expressed across all tissues. Using quantitative real-time PCR (qRT-PCR), we assessed the expression levels of these genes under various hormone treatments and abiotic stress conditions. Notably, SlEIL3 exhibits sustained and significantly elevated expression under salt stress, highlighting its potential role in salt stress response. Consequently, we further investigated the role of SlEIL3 in enhancing salt tolerance. Our findings demonstrate that transient overexpression of SlEIL3 enhances growth characteristics in tomato seedlings under salt stress, improves salt tolerance by reinforcing physiological and biochemical status, and activates stress-related genes. Conversely, transient silencing of SlEIL3 reduces salt tolerance. Thus, SlEIL3 positively regulates salt tolerance in tomatoes. This study provides new insights into the potential biological functions of SlEILs in tomatoes and lays a crucial foundation for future investigations into the functional mechanisms of SlEIL3.