The MAP kinase FvHog1 regulates FB1 synthesis and Ca2+ homeostasis in Fusarium verticillioides

Abstract

The high osmolarity glycerol 1 mitogen-activated protein kinase (Hog1-MAPK) cascade genes are important for diverse biological processes. The activated Hog1 upon multiple environmental stress stimuli enters into the nucleus where it directly phosphorylates transcription factors to regulate various physiological processes in phytopathogenic fungi. However, their roles have not been well-characterized in Fusarium verticillioides. In this study, FvHog1 is identified and functionally analyzed. The findings reveal that the phosphorylation level and nuclear localization of FvHog1 are increased in Fumonisin B1 (FB1)-inducing condition to regulate the expression of FB1 biosynthesis FUM genes. More importantly, the deletion mutants of Hog1-MAPK pathway show increased sensitivity to Ca²⁺ stress and elevated intracellular Ca²⁺ content. The phosphorylation level and nuclear localization of FvHog1 are increased with Ca²⁺ treatment. Furthermore, our results show that FvHog1 can directly phosphorylate Ca²⁺-responsive zinc finger transcription factor 1 (FvCrz1) to regulate Ca²⁺ homeostasis. In conclusion, our findings indicate that FvHog1 is required for FB1 biosynthesis, pathogenicity and Ca²⁺ homeostasis in F. verticillioides. It provides a theoretical basis for effective prevention and control maize ear and stalk rot disease.

Keywords: Ca(2+) homeostasis; FB1; Fusarium verticillioides; Hog1-MAPK pathway; Pathogenicity.