Comparative transcriptomic analysis reveals phenol tolerance mechanism of evolved Chlorella strain

•Comparative transcriptomic analysis was performed for evolved Chlorella strains.•Several genes related to photosynthesis were up-regulated.•Several genes about antioxidant enzymes (SOD, APX, CAT and GR) were up-regulated.•Genes related to astaxanthin, lutein and lycopene biosynthesis were up-regulated.•Tolerance mechanism to high concentration phenol was investigated.

The growth of microalgae is inhibited by high concentration phenol due to reactive oxygen species. An evolved strain tolerated to 500 mg/L phenol, Chlorella sp. L5, was obtained in previous study. In this study, comparative transcriptomic analysis was performed for Chlorella sp. L5 and its original strain (Chlorella sp. L3). The tolerance mechanism of Chlorella sp. L5 for high concentration phenol was explored on genome scale. It was identified that the up-regulations of the related genes according to antioxidant enzymes (SOD, APX, CAT and GR) and carotenoids (astaxanthin, lutein and lycopene) biosynthesis had critical roles to tolerate high concentration phenol. In addition, most of genes of PS I, PS II, photosynthetic electron transport chain and starch biosynthesis were also up-regulated. It was consistent to the experimental results of total carbohydrate contents of Chlorella sp. L3 and Chlorella sp. L5 under 0 mg/L and 500 mg/L phenol.