Expression of Glutamate Dehydrogenase Genes of Mulberry in Morus alba L. and Transgenic Tobacco in Relation to Biotic and Abiotic Stresses

Mulberry (Morus alba L.) is an economically and ecologically important plant with strong stress resistance. Glutamate dehydrogenase (GDH) can catalyze the reversible reaction of alpha-ketoglutarate and NH4+ to glutamate, and plays an important role in resistance to adverse conditions. In this study, two MaGDH genes were cloned, and their biological characteristics studied. The results showed that the MaGDH1 and MaGDH2 protein were localized in the cell membrane, cytoplasm, chloroplasts, and MaGDH1 also localized in mitochondria. These proteins were expressed mainly in flowers. During seed germination, MaGDH1 and MaGDH2 expression levels were the highest when the radicle penetrated the seed coat. Stress tests suggested that MaGDH genes participate in responses to abiotic stress, and that the MaGDH2 protein had an inhibitory effect on the fungal pathogen Ciboria shiraiana, extracted from mulberry fruit. MaGDH overexpression in transgenic tobacco increased the solubility of proteins and chlorophyll content of transgenic tobacco, improving tolerance to salt and drought stresses.