Mitogen-activated protein kinase involved in a signal transduction pathway that is activated by changes in the osmolarity of the extracellular environment. Controls osmotic regulation of transcription of target genes. Also involved in response to UV radiations, heat stress and oxidative stress. Mediates the sensitivity to fludioxonil, an agricultural fungicide. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Activated by dephosphorylation after osmotic stress or in presence of the fludioxonil fungicide. Concentration into the nucleus in response to hyperosmotic conditions is transient and moderate. The TXY motif contains the threonine and tyrosine residues whose phosphorylation activates the MAP kinases. Contrary to what happens in most fungi, is constitutively phosphorylated during non-stress conditions and dephosphorylated after osmotic stress or in presence of the fludioxonil fungicide. Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. MAP kinase subfamily. HOG1 sub-subfamily.