STRESS SIGNAL, MEDIATED BY A HOG1-LIKE MAP KINASE, CONTROLS SEXUAL DEVELOPMENT IN FISSION YEAST

We identified the phh1(+) gene that encodes a MAP kinase as the effect or of Wis1 MAP kinase kinase in fission yeast, which is highly homolog ous with HOG1 of S. cerevisiae. Heterothalic phh1 dsiruptant is phenot ypically indistinguishable from, wis1 deletion mutant, both displaying the same extent of partial sterility and enhanced sensitivity to a va riety of stress, In phh1 disruptant, nitrogen starvation-induced expre ssion of ste11(+), a key controller of sexual differentiation, is mark edly diminished, Ectopic expression of ste11(+) effectively restores f ertility, but not stress resistance, to the phh1 disruptant, These dat a show that stress signal, mediated by a MAP kinase, is required for e fficient start of sexual differentiation.