Comprehensive comparable study of metabolomic and transcriptomic profiling of Isochrysis galbana exposed to high temperature, an important diet microalgal species

Temperature is a crucial environmental factor that affects microalgal growth. However, it remains unclear how microalgae respond to high temperature. In the present study, we investigated the changes in organic acids, total lipids and transcriptomic profiling of Isochrysis galbana, an important diet microalgal species, in response to high temperature. The contents of six organic acids and total lipids, as well as gene expression of I. galbana cultivated at optimal temperature (20 degrees C) versus high temperature (35 degrees C) were compared. The results showed that the contents of oxaloacetic acid, citric acid, alpha-ketoglutaric acid, succinic acid, fumaric acid and malic acid were all decreased in I. galbana cultivated at 35 degrees C. Besides, high temperature decreased the accumulation of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG), while it increased the content of triacylglycerol (TAG). The transcriptomic results of some essential genes involved in tricarboxylic acid cycle (TCA) cycle, lipid metabolism and photosynthetic pathways were consistent with the data from metabolomic analysis. Collectively, comprehensive comparable study of metabolomic and transcriptomic was first conducted to uncover the underlying molecular mechanisms of I. galbana in response to high temperature stress. It was found that a series of biological processes were significantly affected by high temperature, especially TCA cycle, lipid metabolism and photosynthesis. All these lead us to provisionally conclude that the decline of I. galbana in summer was strongly linked to high temperature. Moreover, the findings of our current study had guiding significance for outdoor cultivation of this algal species, which might promote its application in aquaculture.