Functional complementation of yeast mutants to study plant signalling pathways.

The rapidly increasing amount of entirely sequenced genomes generates a need for fast and efficient methods to elucidate gene functions. Functional complementation of yeast mutants, displaying selectable phenotypes, has been used very successfully in the past years to isolate many plant genes involved in signalling, stress response or metabolic pathways. Using the well-characterized Hog1 pathway, a mitogen activated protein (MAP) kinase pathway required for adaptation to osmotic stress in budding yeast, as example, we describe here the isolation of plant protein kinases involved in abiotic stress adaptation in the model plant Arabidopsis thaliana. The osmo-sensitive phenotype of yeast mutants carrying a mutation in the Hog1 pathway allows an easy selection on high osmolarity media, containing i.e. 0.4 M NaCl. By using yeast mutants harbouring deletions in different components of the pathway, for example the MAP kinase kinase Pbs2 and the MAP kinase Hog1, it is furthermore possible to isolate consecutively acting components of a signalling pathway.