Analysis Of Dunaliella Tertiolecta Transcriptome And Hexose Transporter Under Triethylamine Stress

Microalgae that can accumulate lipid accounting for more than 20% of their biomass weight are called oleaginous microalgae.They are becoming increasingly attractive as raw materials for biodiesel production since they have several advantages,including high capacity of carbon fixation,high growth rate,not competing with arable land etc.It is considered as one of the alternative algae for biofuels and a good source of food and nutrient additives.However,under the current experimental conditions,the production of fats and oils cannot meet the production requirements of large-scale industrialization.Dunaliella tertiolecta was the subject of this research,enhancement of the lipid content of which was focused on.The mechanisms of lipid over-accumulation of D.tertiolecta under triethylamine stress condition were systematically investigated.And the lipid accumulation and hexose transporter protein analysis of D.tertiolecta were studied under triethylamine stress.The bioinformatics function of the protein was analyzed,and the expression level was analyzed.The results obtained are as follows.In the transcriptome experiment,approximately 4,500 differentially expressed genes were obtained in the three groups of control and experimental groups.Among them,about3,400 genes are down-regulated and about 3,500 genes are up-regulated.It indicated that the expression of genes and the physiology of cells were significantly changed after triethylamine stress.Differentially expressed genes were mainly associated with glycerol fatty acid synthesis,fatty acid elongation and pentose phosphate pathways.In particular,pathway analysis revealed significant up-regulation of related genes in fatty acid biosynthesis and unsaturated fatty acid synthesis.It is a direct evidence of the response of triethylamine stress to lipid accumulation and fatty acid composition changes.Among the pathways for producing glycerol in the synthesis of glycerol fat,there are acetaldehyde dehydrogenase,glycerol kinase,and phospholipid: diacylglycerol acyltransferase that are up-regulated in gene expression,and the expression of the dihydroxyacetone kinase gene is down-regulated.These up-regulated genes are all expressed in a direction that favors the accumulation of triacylglycerols.It is worth mentioning that glycerol kinase is the initial key step in the production of TAG.Phospholipid: diacylglycerol acyltransferase is the last step of the synthetic pathway.Up-regulation of expression level implies that these two enzymes play an important role in lipid accumulation.The conserved domain analysis revealed that the DtHXTs have a unique domain of the hexose transporter,the MSF transporter family,and the MSF1 transporter family.Subcellular localization analysis revealed that DtHXT1 is a secreted protein,which may anchor on the cell membrane,DtHXT2 localizes on mitochondria,and DtHXT3 and Dt HXT4 localize on plastids.Homologous comparisons showed that DtHXT2 is closely related to the green algae Chlamydomonas reinhardtii,and DtHXT3 has a certain affinity with them.DtHXT1 and DtHXT4 are less related to the above genes.Under the stress of triethylamine,the expression of DtHXT1 was up-regulated by54.55%,while that of DtHXT2 was up-regulated by 26.72%.This facilitated the transport of glucose to the intracellular and mitochondrial transport.On the other hand,Dt HXT3 and DtHXT4 were located on the plastids,and their expression levels were all reduced by about29%,which was favorable for the accumulation of glucose in the chloroplasts and the generation of storage substances such as oils.