Molecular cloning and functional characterization of a glyceraldehyde-3-phosphate dehydrogenase gene from Spartina alterniflora reveals its involvement in salt stress response

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been emerging to be a multifunctional protein involved in various cellular processes, in addition to its role in energy metabolism. In this study, the SaGAPDH gene was cloned from Spartina alterniflora based on the full-length cDNA library. The open reading frame of SaGAPDH was 1014bp, and it was encoding 337 amino acids with a calculated molecular mass of 36.40kDa. Multiple sequence alignment showed that SaGAPDH had high amino acid sequence identity with other plant GAPDHs, and phylogenetic analysis demonstrated that SaGAPDH had a closer affinity to GAPDH in Aeluropus lagopoides (AlGAPDH). Subcellular localization suggested that SaGAPDH was located in cytosol. The recombinant SaGAPDH protein was expressed in Escherichia coli cells to characterize its catalytic activity. And E. coli carrying SaGAPDH gene showed an increased salt stress resistance. SaGAPDH gene was induced by salt stress, and to further investigate its function, transgenic Arabidopsis plants ectopically antisense-overexpressing SaGAPDH was generated. The transgenic Arabidopsis plants showed a specific down-regulation of AtGAPC1 transcript and the GAPDH enzyme activity. They also showed decreased tolerance to salt stress and down-regulation of antioxidant enzymes including catalase, ascorbate peroxidase, superoxide dismutase, and peroxidase, as well as their transcripts. Above results were further confirmed by the aggravation of oxidative damage in SaGAPDH antisense-overexpressing transgenic Arabidopsis lines, which accumulated more reactive oxygen species (ROS) such as superoxide anion (O-) and hydrogen peroxide (H2O2) under salt stress. This study indicated that SaGAPDH may play an important role in response to salt stress by the regulation of redox homeostasis.