A Putative MAPK Kinase Kinase Gene <i>Ssos4</i> is Involved in Mycelial Growth, Virulence, Osmotic Adaptation, and Sensitivity to Fludioxonil and is Essential for SsHog1 Phosphorylation in <i>Sclerotinia sclerotiorum</i>

The high osmolarity glycerol (HOG) pathway, comprising a two-component system and the Hog1 mitogen-activated protein kinase (MAPK) cascade, plays pivotal role in eukaryotic organisms. Previous studies suggested that biological functions of some key genes HOG pathway varied filamentous fungi. In this study, we characterized putative MAPK gene, Ssos4, Sclerotinia sclerotiorum, which encoded phosphotransferase cascade. Compared with wild-type progenitor HA61, deletion mutant ∆Ssos4-63 exhibited impaired mycelial growth, sclerotia formation, increased hyphal branches, decreased virulence. deficiencies were recovered when full-length Ssos4 gene was complemented. Deletion sensitivity to osmotic stresses cell wall agents resistance fludioxonil dimethachlon. Intracellular accumulation not induced treated NaCl phosphorylation SsHog1 also cancelled by Ssos4. Consistent expression levels SsglpA Ssfps1, controlling synthesis close channel under hyperosmotic stress, respectively, detected strain HA61 but ∆Ssos4-63. Moreover, relative level Sshog1 significantly decreased, whereas Ssos5 These results indicated played important roles growth differentiation, virulence, adaptation, fungicide sensitivity, S. sclerotiorum.