Heterologous expression of Sesuvium portulacastrum SOS-related genes confer salt tolerance in yeast

Growth and development of plants are greatly affected by salinity. The salt overly sensitive (SOS) pathway plays a vital role in plants responding to salt stress, and has been reported to contain three components: SOS3 (calcineurin B-like protein 4, CBL4), SOS2 (CBL-interacting protein kinase 24, CIPK24) and SOS1. Our previous study demonstrated that transgenic yeast and Arabidopsis could tolerate salt better when expressed with the cell membrane Na+/H+ antiporter SOS1 from the halophyte Sesuvium portulacastrum. Here, a new CIPK gene (SpCIPK8) and CBL gene (SpCBL10) have been isolated from S. portulacastrum. The expression of SpCIPK8 and SpCBL10 was induced by salinity in roots of S. portulacastrum. An interaction between SpCBL10 and SpCIPK8 was demonstrated in yeast two-hybrid assays. Subsequent analysis found that SpCBL10 could bind the C-terminus of SpCIPK8. Yeast co-expressing SpSOS1, SpCIPK8 and SpCBL10 genes grew better and accumulated more potassium (K+) and less sodium (Na+) under salt stress than yeast that expressed only one or two of these genes, indicating that Na+ was excluded from the cells. Furthermore, we found that the SpCBL10/SpCIPK8 complex regulates the cell membrane Na+/H+ antiporter SpSOS1 to enhance yeast salt tolerance by binding the two serine residues at amino acid positions 1144 and 1146 in the conserved DSPS motif at the C-terminus of SpSOS1. Future studies of the SOS pathway will be greatly aided by these results, which suggest some candidate genes for improving plant salt tolerance.

Automated summary

The growth and development of plants are influenced by salinity. The SOS pathway, consisting of SOS3, SOS2, and SOS1, plays a crucial role in plant response to salt stress. In this study, a new CIPK gene (SpCIPK8) and a CBL gene (SpCBL10) were identified from the halophyte S. portulacastrum. The expression of SpCIPK8 and SpCBL10 was induced by salt stress in the roots of S. portulacastrum. Yeast two-hybrid assays revealed an interaction between SpCBL10 and SpCIPK8. Co-expression of SpSOS1, SpCIPK8, and SpCBL10 in yeast enhanced salt tolerance by excluding Na+ from the cells and increasing K+ accumulation. The findings suggest that the SpCBL10/SpCIPK8 complex regulates the cell membrane Na+/H+ antiporter SpSOS1 and provide candidate genes for improving plant salt tolerance.