Protein tyrosine phosphatases play essential roles in plant growth and development and in plant responses to biotic or abiotic stresses. We recently demonstrated that an atypical dual-specificity protein tyrosine phosphatase in plants, AtPFA-DSP3 (DSP3), negatively regulates plant salt tolerance. Here, we report that a homolog of DSP3, AtPFA-DSP5 (DSP5), affects the response of plants to high-salt conditions. A loss-of-function mutant of DSP5 showed reduced sensitivity to salt treatment at the seed germination and vegetative stages of development while a gain-of-function mutant of DSP5 showed increased sensitivity to salt stress. The salt responses of dsp3dsp5 double-mutant plants were similar to those of dsp3 and dsp5 single-mutant plants. Gel overlay and firefly luciferase complementation assays showed that DSP5 interacts with MPK3 and MPK6 in vitro and in vivo. These results indicate that DSP5 is a novel negative regulator of salt responses in Arabidopsis that interacts directly with MPK3 and MPK6.
Keywords: Arabidopsis; AtPFA-DSP5; protein tyrosine phosphatase; salt stress.