Abstract
Over the last decade, increasing attention has been paid to the
molecular adaptations used by organisms to cope with thermal stress.
However, to date, few studies have focused on thermophilic species
living in hot, arid climates. In this study, we explored molecular
adaptations to heat stress in the thermophilic ant genus Cataglyphis,
one of the world’s most thermotolerant animal taxa. We compared heat
tolerance and gene expression patterns across six phylogenetically
distant species that live in different habitats and experience different
thermal regimes. We found that all six species had similar heat
tolerance levels and critical thermal maxima. Furthermore, the
transcriptome analyses revealed that, although the number of
differentially expressed genes varied widely for the 6 species (from 54
to 1,118), many were also shared. Functional annotation of the
differentially expressed and co-expressed genes then showed that the
biological pathways involved in heat-shock responses were similar among
species and were associated with four major processes: the regulation of
transcriptional machinery and DNA metabolism; the preservation of
proteome stability; the elimination of toxic residues; and the
maintenance of cellular integrity. Overall, our results suggest that
molecular responses to heat stress have been evolutionarily conserved in
the ant genus Cataglyphis and that their versatility may help workers
withstand temperatures close to their physiological limits.