Revealing the moleclar mechanisms of temperature acclimation and adaptation in marine diatoms with transcriptional responses to sub- and supra-optimal growth temperatures

Background: Ocean temperatures are projected to increase over the coming century, with dramatic consequences for the marine biosphere. Diatoms are important contributors to marine primary production and the ocean carbon cycle, yet the molecular mechanisms that regulate their acclimation and adaptation to temperature are poorly understood. Method: Here we use a transcriptomic approach to identify the molecular mechanisms associated with temperature acclimation and adaptation in closely related colder- and warmer-adapted diatom species. Results: We find contrasting patterns of differential expression at sub- and supra-optimal temperatures across the two species, which may be due to adaptive changes in baseline expression. Frontloaded and divested pathways indicate protein processing machinery, membrane structure, and the balance between temperature-independent photosynthesis and temperature-dependent metabolism are key elements of adaptation to temperature changes. Conclusions: Our findings suggest that transcriptional frontloading and divestment may provide a framework to interpret diatom acclimation and adaptation to temperature and success under future warming. RNA profiles of two closely related Chaetoceros species cultured under their respective optimal temperature (Tmax), sub-optimal temperature (Tsub), and supra-optimal temperature (Tsup) were generated in triplicates with RNA-Seq using Illumina HiSeq 2000. The SRA accessions for the samples of CCMP158 are SRR8009948, SRR8009947, SRR8009955, SRR8009951, SRR8009952, SRR8009959, SRR8009958, SRR8009957, SRR8009954. The SRA accessions for the samples of CCMP160 are SRR8009953, SRR8009950, SRR8009949, SRR8009945, SRR8009960, SRR8009946, SRR8009956, SRR8009944, SRR8009943. The Bioproject accesssion is PRJNA495610.