AtPFA-DSP5 interacts with MPK3/MPK6 and negatively regulates plant salt responses.

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 double-mutant plants were similar to those of and single-mutant plants. Gel overlay and firefly luciferase complementation assays showed that DSP5 interacts with MPK3 and MPK6 and . These results indicate that DSP5 is a novel negative regulator of salt responses in that interacts directly with MPK3 and MPK6.