Overexpression of MpGR-RBP1, a glycine-rich RNA-binding protein gene from Malus prunifolia (Willd.) Borkh., confers salt stress tolerance and protects against oxidative stress in Arabidopsis

Glycine-rich RNA-binding proteins (GR-RBPs) are involved in the post-transcriptional regulation of genes. Although they are known to have roles in plant responses to environmental stresses, their functions in diverse species under stress conditions are still unverified. We assessed the biological roles of MpGR-RBP1, a GR-RBP from Malus prunifolia that is up-regulated by salinity, oxidation, or abscisic acid. Under control of the 35S promoter, its ectopic expression in Arabidopsis resulted in accelerated seed germination and seedling growth in two transgenic lines when plants were exposed to high salt or oxidative stress. This gene also contributed to the enhancement of salt tolerance in transgenic Arabidopsis plants. Consistently, the enhanced tolerance was confirmed by the changes of physiological parameters including electrolyte leakage, chlorophyll concentration and malondialdehyde accumulation. The accumulation of reactive oxygen species (ROS) in the transgenics was appreciably decreased under salt stress. In addition, MpGR-RBP1 had an effect on stomatal closure under saline conditions. Taken together, these results demonstrate that MpGR-RBP1 affects the growth and tolerance of salt-stressed Arabidopsis plants. Its functioning may be due, in part, to its influence on ROS accumulation and stomatal behavior, thereby leading to improved salt tolerance.