Evaluation of Shifts of Gene Transcription Levels of Unicellular Green Alga Chlamydomonas reinhardtii Due to UV-C Irradiation

Green algae produce valuable lipids as carbon-recycling resources. Collecting whole cells with the intracellular lipids could be efficient without cell burst; however, direct use of the cells causes microbial contamination in environments. Then, UV-C irradiation was selected to satisfy the requirements of avoiding the cell burst and sterilizing cells with Chlamydomonas reinhardtii. UV-C irradiation with 1.209 mW center dot cm(-2) showed enough sterilization activity for 1.6 x 10(7) cells center dot mL(-1) of C. reinhardtii in a depth of 5 mm for 10 min. The irradiation showed no effects to composition and contents of the intracellular lipids. From the viewpoint of transcriptomic analysis, the irradiation displayed possibilities of (i) inhibition of the synthesis of lipids due to decrement of the transcription of related genes, such as diacylglycerol acyl transferase and cyclopropane fatty acid synthase, and (ii) activation of lipid degradation and the production of NADH(2)(+) and FADH(2) due to increment of the transcription of related genes, such as isocitrate dehydrogenase, dihydrolipoamide dehydrogenase and malate dehydrogenase. Irradiation until cell death could be insufficient to shift the metabolic flows even though the transcriptions were already shifted to lipid degradation and energy production. This paper is the first report of the response of C. reinhardtii to UV-C irradiation on the transcription level.

Automated summary

UV-C irradiation can efficiently collect intracellular lipids from green algae cells without cell burst and microbial contamination, while also potentially affecting lipid synthesis and degradation pathways. This study provides the first report on the transcriptional response of C. reinhardtii to UV-C irradiation.