THE PISUM-SATIVUM MAP KINASE HOMOLOG (PSMAPK) RESCUES THE SACCHAROMYCES-CEREVISIAE HOG1 DELETION MUTANT UNDER CONDITIONS OF HIGH OSMOTIC-STRESS

Previous analysis of the MAP kinase homologue from Pisum sativum (PsMA PK) revealed a potential MAP kinase motif homologous to that found in eukaryotic cdc2 kinases. Sequence comparison showed a 47% identity on amino acid sequence basis to the Saccharomyces cerevisiae Hog1p MAP ki nase involved in the osmoregulatory pathway. Under conditions of salt- stress aberrant morphology of a hog1 deletion mutant was completely re stored and growth was partially restored by expression of the PsMAPK. This shows that PsMAPK is functionally active as a MAP kinase in S. ce revisiae. Comparison of PsMAPK with other kinases involved in osmosens itivity, showed a high degree of homology and implicates a possible ro le for PsMAPK in a P. sativum osmosensing signal transduction pathway.