动物实验,硅藻油脂 z-bo 2020-08-31 463

　　Recently, Hu Hanhua, an associate researcher at the Institute of Hydrobiology, Chinese Academy of Sciences, took the model species Phaeodactylum tricornutum, a model species studied on diatoms, as the object, and revealed how different metabolic pathways promote the flow of carbon to the synthesis of triglycerides during the accumulation of diatom oil.

　　Diatoms are an important group of algae. As a major primary producer, they account for about one-fifth of global primary production, which is equivalent to the net primary production of the entire tropical rainforest. Unlike most algae, the product of diatom assimilation is mainly oil or chrysophyll. The oil is stored in the cells in the form of oil droplets, and the content can account for 40-60%. Therefore, it is considered to be one of the most suitable biodiesel raw materials. However, the molecular mechanism of its oil accumulation is still unclear.

　　Recently, the research group of Hu Hanhua, an associate researcher of the Institute of Hydrobiology, Chinese Academy of Sciences, used the model species Phaeodactylum tricornutum to study diatoms, and revealed how different metabolic pathways promote the flow of carbon to the synthesis of triglycerides during the accumulation of diatom oil.

　　They first used subtractive hybridization and found that a gene related to leucine degradation, MCC2, was significantly up-regulated during the accumulation of oil. It is generally believed that the accumulation of oil is accompanied by the restriction of nutrients, so under the condition of restriction of nutrients, the degradation of amino acids is an inevitable result. But where is the degradation of amino acids? Is it all related to the accumulation of fat? There is no direct evidence for these problems.

　　The analysis by fluorescence quantitative PCR and non-labeled quantitative proteomics (completed in cooperation with researcher Ge Feng from the Institute of Aquatics) showed that in addition to the degradation of amino acids, glycolysis, tricarboxylic acid cycle, pyruvate metabolism, fatty acid and The levels of proteins related to triglyceride synthesis and other pathways were significantly increased. It shows that in the process of oil accumulation, the carbon stream produced by amino acid degradation and cellular glycolysis enters the tricarboxylic acid cycle, and then enters the chloroplast via malic acid or directly in the form of pyruvate for fatty acid synthesis.

　　Functional verification results showed that the triglyceride synthesis of MCC2 knockdown algae strain was reduced by 28~37%. Studies have shown that under nutritionally limited conditions, up to 40% of Phaeodactylum tricornutum lipids are converted from degradation of other components of the cell. It can be seen that the degradation of branched-chain amino acids, especially leucine, may play a major role in the accumulation of Phaeodactylum tricornutum oil. Analysis of metabolite levels showed that the degradation of the three branched chain amino acids in MCC2 knockdown algae strains was inhibited to varying degrees.

　　Although the content of glutamine, arginine, glutamic acid, proline, alanine, ornithine and aspartic acid is much higher than that of the three branched chain amino acids, before the accumulation of oil, these amino acids The content quickly dropped to an extremely low level. Experiments further prove that these amino acids are directly or indirectly related to the unique urea cycle of diatoms, and they are stored in the cells through the decomposition of the urea cycle to form ammonia and carbon dioxide or synthetic polyamines before the cells are deficient in nitrogen. Experiments also proved that the degradation of valine is carried out by first forming leucine. Their experiment demonstrated for the first time that the carbon flow from cellular glycolysis and branched-chain amino acid degradation led to the accumulation of lipids in diatom cells.