Edited by Francesc PosasCoordination and cross talks of MAPK pathways are critical for signaling efficiency, but their mechanisms are not well understood. Slt2, the MAP kinase of cell wall integrity pathway (CWI), is activated by heat stress even in the absence of upstream components of this pathway, suggesting a supplementary input for Slt2 activation. Here, we identify a new interaction of Ste11 and Mkk1, mediated by Nst1 that connects the high-osmolarity glycerol and pheromone pathways directly to CWI pathway in response to heat and pheromone. We suggest that Ser 407 and Thr 411 are novel residues of Mkk1 activated by these MAPK pathways.

TRP1 is a frequently used auxotrophic marker for genetic modifications and selections in trp(-) budding yeast strains, including the commonly used wild-type strain W303a. However, we found that introduction of the TRP1 gene into a trp(-) strain significantly affected vegetative growth at low and high temperatures. Therefore, caution should be needed when working in a trp(-) background strain and using the TRP1 marker to study stress response phenotypes, particularly when analyzing temperature sensitivities.