Spatial analysis of gene regulation reveals new insights into the molecular basis of upper thermal limits

The cellular stress response has long been the primary model for studying the molecular basis of thermal adaptation, yet the link between gene expression, RNA metabolism and physiological responses to thermal stress remains largely unexplored. We address this by comparing the transcriptional and physiological responses of three geographically distinct populations of D. melanogaster from eastern Australia in response to, and recovery from, a severe heat stress with and without a pre-stress hardening treatment. We focus on Starvin (stv), recently identified as an important thermally responsive gene. Intriguingly, stv encodes seven transcripts from alternative transcription sites and alternative splicing, yet appears to be rapidly heat-inducible. First, we show genetic differences in upper thermal limits of the populations tested. We then demonstrate that the stv locus does not ubiquitously respond to thermal stress but is expressed as three distinct thermal and temporal RNA phenotypes (is...