Overexpression of , and in Alfalfa (a L.) Provides Different Extents of Enhanced Alkali and Salt Tolerance Due to Functional Specialization of .

Rare cold-inducible 2/plasma membrane protein 3 () genes are ubiquitous in plants and belong to a multigene family whose members respond to a variety of abiotic stresses by regulating ion homeostasis and stabilizing membranes, thus preventing damage. In this study, the expression of , , and under high-salinity, alkali and ABA treatments was analyzed. The results showed that the expression of , , and in alfalfa ( L.) was induced by salt, alkali and ABA treatments, but there were differences between gene expression under different treatments. We investigated the functional differences in the MsRCI2A, MsRCI2B, and MsRCI2C proteins in alfalfa ( L.) by generating transgenic alfalfa plants that ectopically expressed these s under the control of the CaMV35S promoter. The -overexpressing plants exhibited different degrees of improved phenotypes under high-salinity stress (200 mmol.L NaCl) and weak alkali stress (100 mmol.L NaHCO, pH 8.5). Salinity stress had a more significant impact on alfalfa than alkali stress. Overexpression of s in alfalfa caused the same physiological response to salt stress. However, in response to alkali stress, the three proteins encoded by s exhibited functional differences, which were determined not only by their different expression regulation but also by the differences in their regulatory relationship with s or .