Histidine kinase involved in a two-component signaling pathway that regulates cell wall mannan biosynthesis. Part of the bifurcated SLN1-YPD1-SKN7/SSK1 two-component regulatory system, which controls activity of the HOG1 pathway and gene expression in response to oxidative stress and probably also to changes in the osmolarity of the extracellular environment. Plays a role in the regulation of alternative oxidase (AOX) gene family expression. Required for hyphal formation and virulence