We have cloned and characterized a novel Aspergillus nidulans histidine kinase gene, tcsB, encoding a membrane-type two-component signaling protein homologous to the yeast osmosensor Sln1p, which transmits signals through the Hog1p-MAPK cascade in yeast in response to osmotic stimuli. Overexpression of the tcsB cDNA suppressed the lethality of the temperature-sensitive osmosensing-defective yeast mutant sln1-ts. However, tcsB cDNAs in which the conserved phosphorylation site His552 or phosphorelay site Asp989 had been substituted failed to complement the sln1-ts mutant. Introduction of the tcsB cDNA into the yeast double mutantsln1-delta sho1-delta, which lacks two osmosensors, suppressed lethality in high-salinity media and activated the HOG1 MAPK. These results imply that TcsB functions as an osmosensor histidine kinase. We constructed an A. nidulans strain lacking the tcsB gene (tcsB-delta) and examined its phenotype. However, unexpectedly, the tcsB-delta strain did not exhibit a detectable phenotype in either hyphal development or morphology on standard or stress media. The result suggests that A. nidulans has more complex and robust osmoregulatory systems than the yeast SLN1-HOG1 MAPK cascade. Functional analysis of other histidine kinase genes homologous to yeast YPD1 and SSK1 will be also discussed.
Fungal Genet. Newsl. 50 (Supl):abstract
Full conference title:
22nd Fungal Genetics Conference
- Fungal Genetics Conference 22nd (2001)