Divergence in theSaccharomycesspecies’ heat shock response is indicative of their thermal tolerance

Abstract

AbstractTheSaccharomycesspecies have diverged in their thermal growth profile. BothS. cerevisiaeandS. paradoxusgrow at temperatures well above the maximum growth temperature ofS. kudriavzeviiandS. uvarum, but grow more poorly at lower temperatures. In response to thermal shifts, organisms activate a stress response that includes heat shock proteins involved in protein homeostasis and acquisition of thermal tolerance. To determine whetherSaccharomycesspecies have diverged in their response to temperature we measured changes in gene expression in response to a 12°C increase or decrease in temperature for fourSaccharomycesspecies and their six pairwise hybrids. To ensure coverage of subtelomeric gene families we sequenced, assembled and annotated a completeS. uvarumgenome. All the strains exhibited a stronger response to heat than cold treatment. In response to heat, the cryophilic species showed a stronger response than the thermophilic species. The hybrids showed a mixture of parental stress responses depending on the time point. After the initial response, hybrids with a thermophilic parent were more similar toS. cerevisiaeandS. paradoxus, and theS. cerevisiaexS. paradoxushybrid showed the weakest heat shock response. Within the hybrids a small subset of temperature responsive genes showed species specific responses but most were also hybrid specific. Our results show that divergence in the heat shock response is indicative of a strain’s thermal tolerance, suggesting that cellular factors that signal heat stress or resolve heat induced changes are relevant to thermal divergence in theSaccharomycesspecies.