S ‐nitrosylation of PTP1 positively regulates MPK6 activity in response to salt or cold stress in Arabidopsis thaliana

Nitric oxide (NO), an essential signaling molecule, greatly affects how plants respond to salinity or cold stress. It can impact specific protein activity via S-nitrosylation. We found that protein tyrosine phosphatase 1 (PTP1) participates in the response of Arabidopsis thaliana (A. thaliana) to both high-salt and freezing conditions. NO facilitated PTP1 S-nitrosylation at cysteine (Cys)-41, resulting in increased salt tolerance and altered sensitivity to freezing. Additionally, this process reduced the dephosphorylation activity of PTP1 and activated mitogen-activated protein kinase 6 (MPK6) in plants exposed to high-salt and freezing conditions. MPK6 activation increased plant resistance to salt stress but attenuated plant freezing tolerance. Genetic analysis revealed that the effects of PTP1 on salinity and freezing stresses were dependent on MPK6 activity. Collectively, our findings show a new mechanism by which NO negatively influences the enzymatic activity of PTP1 via S-nitrosylation at Cys-41. This process, in turn, influences the levels of phosphorylated MPK6 in A. thaliana, enhancing its ability to tolerate salt loading and to respond to freezing conditions.