STK1, a MAP kinase gene from Setosphaeria turcica, confers preferable tolerance to sodium salt stress

Setosphaeria turcica, a serious fungal plant pathogen that causes northern corn leaf blight, is a filamentous, heterothallic ascomycete. STK1 gene, cloned from S. turcica, encodes a mitogen-activated protein kinase (MAPK) that is homologous to Hog1 inSaccharomyces cerevisiae and other MAP kinases related to osmoregulation in filamentous fungi. Its encoded protein, Stk1, contains all the conserved domains that characterize Hog1-homologues. STK1 expression restores the S. cerevisiae hog1 null mutant phenotype in the complementation test under salt and oxidative stress. The signal transduction pathway may be similar between S. turcica and S. cerevisiae, in which STK1plays a key function in resistance to environmental stress. Transformants with STK1 are more tolerant of 1 M NaCl than the wild-type strains based on the growth rate test and determination of intracellular glycerol concentration.   Key words: Mitogen-activated protein kinase (MAPK), Setosphaeria turcica.