Time‐resolved transcriptome analysis of Scenedesmus obliquus HTB1 under 10% CO2 condition

Certain microalgal species can grow under high CO 2 concentrations providing potential for mitigating CO 2 pollution in flue gas produced by power plants. Microalga Scenedesmus obliquus strain HTB1 was isolated from the Chesapeake Bay and grow rapidly in a high level of CO 2 . However, little is known about the molecular responses of HTB1 to high CO 2 levels. Here, we investigated how HTB1 responds to 10% CO 2 using the time‐resolved transcriptome analysis. Gene expression profiles indicated that HTB1 responds quickly (in 2 h) and becomes adaptive within 12 h when exposed to 10% CO 2 . Interestingly, certain genes of light‐harvesting, chlorophyll synthesis and carbon fixation (i.e. rbcS) were up‐regulated at 10% CO 2 , and these functional responses are consistent with the increased photosynthesis efficiency and algal biomass under 10% CO 2 . Nitrate assimilation was strongly enhanced, with amino acid biosynthesis and aminoacyl tRNA biosynthesis genes being markedly up‐regulated, indicating that HTB1 actively takes up nitrogen and accelerates protein synthesis at 10% CO 2 . Carbon metabolism including fatty acid biosynthesis and TCA cycle was enhanced at 10% CO 2 , supporting the earlier observation of increased lipid content of Scenedesmus sp. under high CO 2 levels. Interestingly, key genes like RuBisCO (rbcL) and carbonic anhydrase in carboxysomes did not respond actively to 10% CO 2 , implying that exposure to 10% CO 2 has little impact on the carbon concentrating mechanisms and CO 2 fixation of the Calvin cycle. It appears that HTB1 can grow rapidly at 10% CO 2 without significant metabolic changes in carbon fixation and ATP synthesis.

Abstract licence: CC BY-NC-ND

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   RSEM: accurate transcript quantification from RNA-Seq data with or without a reference genome · 2011

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