Gene expression responses to thermal shifts in the endangered lichen Lobaria pulmonaria

Anthropogenic climate change has led to unprecedented shifts in
temperature across many ecosystems. In a context of rapid environmental
changes, acclimation is an important process as it may influence the
capacity of organisms to survive under novel thermal conditions.
Mechanisms of acclimation could involve upregulation of stress response
genes involved in protein folding, DNA damage repair and the regulation of
signal transduction genes, along with a simultaneous downregulation of
genes involved in growth or cell cycle, in order to maintain cellular
functions and equilibria. We transplanted Lobaria pulmonaria lichens
originating from different forests to determine the relative effects of
long-term acclimation and genetic factors on the variability in expression
of mycobiont and photobiont genes. We found a strong response of mycobiont
and photobiont to high temperatures, regardless of sample origin. The
green-algal photobiont had an overall lower response than the mycobiont.
The gene expression of both symbionts was also influenced by acclimation
to transplantation sites and by genetic factors. Lobaria pulmonaria seems
to have evolved powerful molecular pathways to deal with environmental
fluctuations and stress and can acclimate to new habitats by
transcriptomic convergence. Although L. pulmonaria has the molecular
machinery to counteract short-term thermal stress, survival of lichens
like L. pulmonaria depends mostly on their long-term positive carbon
balance, which can be compromised by warmer temperatures and reduced
precipitation, and both these outcomes have been predicted for Central
Europe in connection with global climate change.