Transcriptomic Temperature Stress Responses Show Differentiation Between Biomes for Diverse Plants

Plants are foundational to terrestrial ecosystems, and because they are sessile, they are particularly reliant on physiological plasticity to respond to weather extremes. However, variation in conserved transcriptomic responses to temperature extremes is not well described across plants from contrasting environments. Beyond molecular responses, photosystem II thermal tolerance traits are widely used to assay plant thermal tolerance. To explore options for improving the prediction of thermal tolerance capacity, we investigated variation in the transcriptomic stress responses of 20 native Australian plant species from varied environments, using de novo transcriptome assemblies and 188 RNA-sequencing libraries. We documented gene expression responses for biological processes, to both hot and cold temperature treatments, that were consistent with conserved transcriptomic stress responses seen in model species. The pathways with the most significant responses were generally related to signaling and stress responses. The magnitude of some responses showed differentiation between the species from contrasting arid, alpine, and temperate biomes. This variation among biomes indicated that postheat exposure, alpine and temperate species had greater shifts in expression than arid species and alpine species had weaker responses to the cold treatment. Changes in the median expression of biological processes were also compared to plasticity in photosystem II heat and cold tolerance traits. Gene expression responses showed some expected relationships with photosystem II thermal tolerance plasticity, but these two response types appeared to be mostly independent. Our findings demonstrate the potential for using variation in conserved transcriptomic traits to characterize the sensitivity of plants from diverse taxa to temperature extremes.