The maize hexokinase gene ZmHXK7 confers salt resistance in transgenic Arabidopsis plants

The hexokinase (HXK) gene family, whose members play vital roles in sugar induction signals and glycolysis in organisms, is widely found in plants. Although some hexokinase genes have been studied in maize, a systematic report of the gene family and its role in plant resistance is lacking. In this study, 10 hexokinase genes were systematically identified in maize based on the maize genome-wide database. Phylogenetic analysis divides the maize HXK protein family into four clusters. Prediction of cis-regulatory elements showed that a number of elements responding to abiotic stress exist in the promoter of hexokinase genes. The expression profile of these genes, originated from B73, showed that different members of hexokinase genes are highly expressed in roots and leaves of maize under salt or drought stress, which is similar to that of Mo17.The coding sequence of ZmHXK7 gene, isolated from maize B73, was constructed into plant expression vector pMDC45 and then transformed into athxk3 (Salk_022188C). By hyg resistance detection, PCR analysis, and western blot confirmation, the homozygous progenies of transgenic Arabidopsis lines were identified. Subcellular localization analysis showed that the ZmHXK7 gene was located in cytosol. Seedling growth and salt stress inhibition in complementary mutant plants of ZmHXK7 gene were significantly improved, and enhanced salt tolerance was displayed. Our study provides insights into the evolution and expression patterns of the hexokinase gene and show that maize ZmHXK7 proteins play an important role in resisting salt stress, which will be useful in plant breeding for abiotic stress resistance. Keywords: Maize, Hexokinase, Abiotic stress, Gene expression, salt tolerance