Dephosphorylation of CatC at Ser-18 improves salt and oxidative tolerance via promoting its tetramerization in rice

Catalase (CAT) is a vital antioxidant enzyme, while phosphorylation pivotally regulates its function. Many phosphosites have been identified in CAT, but their functions remained largely elusive. We functionally studied five phosphoserines (Ser-9,-10,-11,-18, and-205) of CatC in rice (Oryza sativa L.). Phospho-Ser-9 and -11 and dephospho-Ser-18 promoted the enzymatic activity of CatC and enhanced oxidative and salt tolerance in yeast. Phosphorylation status of Ser-18 did not affect CatC peroxisomal targeting and stability, but dephospho-Ser-18 promoted CatC tetramerization to enhance its activity. Moreover, overexpression of dephospho-mimic form CatCS18A in rice significantly improved the tolerance to salt and oxidative stresses by inhibiting the H2O2 accumulation. Together, these results elucidate the mechanism underlying dephosphorylation at Ser-18 pro-motes CatC activity and salt tolerance in rice. Ser-18 is a promising candidate phosphosite of CatC for breeding highly salt-tolerant rice.

Automated summary

Catalase (CAT) is an antioxidant enzyme whose function is regulated by phosphorylation. In this study, we investigated the functions of five phosphorylated serines (Ser-9, -10, -11, -18, and -205) in CatC in rice. We found that phosphorylated Ser-9 and -11, as well as dephosphorylated Ser-18, promoted the enzymatic activity of CatC and increased oxidative and salt tolerance in yeast. Dephosphorylated Ser-18 also enhanced CatC tetramerization to enhance its activity.