Genome-wide analysis of the MGT gene family in apple and functional identification of MdMGT6 under saline-alkali stress.

MdMGT6 has a positive regulatory effect on A. thaliana, tobacco and apple calli under saline-alkali stress. As a major apple (Malus domestica) producing area, soil salinization is one of the important factors affecting apple yield in Northwest China. MGT (Magnesium transporter protein) family genes play a key role in plant growth and development and abiotic stress response. In this study, a total of 12 genes were identified by genome-wide identification of apple. Construct a phylogenetic tree among different species and divide all members into six subgroups. There are multiple stress-related regulatory elements in the MdMGTS promoter region, suggesting that it may be involved in abiotic stress. The qRT-PCR results showed that MdMGT6 was significantly highly expressed under saline-alkali stress. Despite this discovery, the mechanism of how MdMGT6 responds to saline-alkali stress has not been explored. To investigate this question, the MdMGT6 (MD10G1056700) gene were successfully cloned from Malus domestica and genetically transformed it in Arabidopsis thaliana, tobacco and apple calli. The resistance to saline-alkali stress was identified by a series of physiological and biochemical experiments. The results showed that compared with the wild type, the chlorophyll, Proline (Pro) content and antioxidant enzyme activity of the transgenic plants were significantly increased under saline-alkali stress, while the Malondialdehyde (MAD) and Relative conductivity (REC) content were decreased. In addition, saline-alkali stress related genes were significantly higher in the overexpression lines than in the WT lines. These results indicate that MdMGT6 can respond to saline-alkali stress and play a positive regulation role.