Transcriptional acclimation to warming temperatures of the Australian alpine herb Wahlenbergia ceracea

Understanding the molecular basis of plant heat tolerance helps to predict the consequences of climate warming on plant performance, particularly in vulnerable environments. Our current understanding comes primarily from studies in Arabidopsis thaliana (Arabidopsis) and select crops exposed to short and intense periods of heat stress. In this study we sought to characterise the transcriptomic responses of Wahlenbergia ceracea (W. ceracea), an Australian alpine herb, to growth under sustained moderate warming. We compared responses of pre-defined tolerant and sensitive lines, based on measures of photosynthetic thermostability, to growth under cool (24/15 {degrees}C day/night) or warm (30/20 {degrees}C day/night) temperatures to identify the pathways involved in heat tolerance and acclimation. Under warmer growth temperatures, W. ceracea up-regulated genes involved in RNA metabolism, while down-regulating those involved in photosynthesis and pigment metabolism. In tolerant lines, genes related to photosystem II and light-dependent photosynthetic reactions were more strongly down- regulated. This suggests that the regulation of electron transport and its components may be involved in thermal acclimation. Our results also highlight the importance of hormonal gene networks, particularly those responsive to ethylene, during longer-term moderate warming. In conclusion, our results point to post-transcriptional processes and the stabilisation of the electron transport chain as candidate mechanisms for thermal acclimation in heat-tolerant W. ceracea. The study also revealed many temperature-responsive genes with no detectable ortholog in Arabidopsis, whose characterization may enhance our understanding of physiological acclimation and have relevance for the biotechnological improvement of threatened species and crops.