Overexpression of the soybean GmWNK1 altered the sensitivity to salt and osmotic stress in Arabidopsis

The WNK (With No Lysine K) serine-threonine kinases have been shown to be osmosensitive regulators and are critical for cell volume homeostasis in humans. We previously identified a soybean root-specific WNK homolog, GmWNK1, which is important for normal late root development by fine-tuning regulation of ABA levels. However, the functions of WNKs in plant osmotic stress response remains uncertain. In this study, we generated transgenic Arabidopsis plants with constitutive expression of GmWNK1. We found that these transgenic plants had increased endogenous ABA levels and altered expression of ABA-responsive genes, and exhibited a significantly enhanced tolerance to NaCl and osmotic stresses during seed germination and seedling development. These findings suggest that, in addition to regulating root development, GmWNK1 also regulates ABA-responsive gene expression and/or interacts with other stress related signals, thereby modulating osmotic stress responses. Thus, these results suggest that WNKs are members of an evolutionarily conserved kinase family that modulates cellular response to osmotic stresses in both animal and plants.