MAP Kinase FgHog1 and Importin β FgNmd5 Regulate Calcium Homeostasis in Fusarium graminearum .
Lixin ZhangYiqing LiLanlan DongKewei SunHao LiuZhonghua MaLeiyan YanYanni YinPublished in: Journal of fungi (Basel, Switzerland) (2023)
Maintaining cellular calcium (Ca 2+ ) homeostasis is essential for many aspects of cellular life. The high-osmolarity glycerol (HOG) mitogen-activated protein kinase (MAPK) pathway responsible for signal integration and transduction plays crucial roles in environmental adaptation, especially in the response to osmotic stress. Hog1 is activated by transient Ca 2+ increase in yeast, but the functions of the HOG pathway in Ca 2+ homeostasis are largely unknown. We found that the HOG pathway was involved in the regulation of Ca 2+ homeostasis in Fusarium graminearum , a devastating fungal pathogen of cereal crops. The deletion mutants of HOG pathway displayed increased sensitivity to Ca 2+ and FK506, and elevated intracellular Ca 2+ content. Ca 2+ treatment induced the phosphorylation of FgHog1, and the phosphorylated FgHog1 was transported into the nucleus by importin β FgNmd5. Moreover, the increased phosphorylation and nuclear accumulation of FgHog1 upon Ca 2+ treatment is independent of the calcineurin pathway that is conserved and downstream of the Ca 2+ signal. Taken together, this study reported the novel function of FgHog1 in the regulation of Ca 2+ homeostasis in F. graminearum , which advance the understanding of the HOG pathway and the association between the HOG and calcineurin pathways in fungi.