The SNARE protein TcSYP121 from the recretohalophyte Tamarix chinensis increases salt tolerance in plants by modulating vesicle trafficking

Soil salinization is a major environmental challenge that impedes plant growth, and Tamarix chinensis is a typical recretohalophyte. To elucidate the salt tolerance mechanism of halophytes and identify highly efficient salt tolerance genes, the morphological, physiological and molecular mechanisms of T. chinensis under salt stress were assessed. Transmission electron microscopy of the salt glands revealed a large number of vesicles and synaptosomes after exposure to 400 mmol · L -1 NaCl. Physiological parameters, including antioxidant enzyme activities (POD and SOD), proline content, soluble sugar content, soluble protein content and the salt secretion rate, manifested consistent increasing trends under NaCl stress. Transcriptome profiling revealed that DEGs associated with vesicular transport and membrane transport played important roles in the response to salinity stress in T. chinensis . Expression of the SNARE protein TcSYP121 was significantly upregulated by salinity stress, and expression of the TcSYP121 gene was significantly decreased after treatment with brefeldin A (BFA), a specific inhibitor of vesicle transport. Transient overexpression of the TcSYP121 gene in T. chinensis increased salt stress tolerance. In contrast, virus-induced gene silencing (VIGS) of TcSYP121 reduced salt tolerance in T. chinensis . The heterologous expression of the T. chinensis TcSYP121 gene in Arabidopsis thaliana significantly improved the salt tolerance of transgenic A. thaliana by promoting ion transport via increasing the length of the Golgi membrane and the size of secretory vesicles, amplifying antioxidant enzyme activity and maintaining low ROS levels. In summary, our results not only reveal that vesicle trafficking is crucial for the salt-stress response and survival but also suggest the use of the vesicle transport-related gene TcSYP121 for the cultivation of salt-tolerant crop varieties in saline‒alkali environments.