Study On The Molecular Mechanism Of DHA Accumulation Promoted By Low Temperature In Schizochytrium Sp.TIO01

Docosahexaenoic acid(DHA)is a long-chain polyunsaturated fatty acids,which is essential to the nervous system development and eye protection.Schizochytrium is a kind of lower Marine fungi,it has fast growth speed,short fermentation period and high polyunsaturated fatty acids yield and become one of the hot strains in industrialized production of DHA.According to published reports and the early experiment,it is concluded that low temperature could significantly improve the accumulation of DHA in Schizochytrium.In order to get the key regulatory proteins involved in the biological process,this paper selected Schizochytrium at 30? logarithmic phase(30 log)and 15? logarithmic phase(15 log),to do physiological and biochemical index determination,transcriptome sequencing,analysis of Differently Expressed Genes and Q-PCR verification et.al.Attempted to study on the molecular mechanism of low temperature promoting DHA accumulation at the transcriptional level.The main research results are shown as follows:1)The percentage DHA in total fatty acid content of 30?logarithmic phase and 15? logarithmic phase were 48.36% and 67.38%,respectively.2)We generated about 100.01 Gb bases in total after Illumina Hiseq sequencing.Then assemble all samples together,we got 43,550 Unigenes,the total length,average length,N50,and GC content of Unigenes are 54,436,700 bp,1,249 bp,2,526 bp,and 47.60 %,respectively.DEG results found that there are 376 up-regulated genes and 50 down-regulated genes in 30 ? log vs 15 ?.3)Selected 10 differently expressed genes in real-time fluorescent quantitative PCR,the results show that there were 9 genes of which the differentially expressed trend were consistent with the transcriptome data,indicating that the transcriptome data were accurate and credible.4)Based on the KEGG enrichment analysis of differentially expressed genes,we found that in fatty acid metabolism pathway associated with DHA synthesis,most of the related genes of fatty acid synthase in FAS pathway and PKS pathway were all down regulated at low temperature.But in the downstream pathway,the genes related to ?9 desaturase,?12 desaturase,?6 desaturase,?9 elongase,?8 desaturase and ?4 desaturase were up regulated.So we speculated that these genes play a key role in the process of DHA accumulation at low temperature.At the same time,we found some genes related to calmodulin were also up regulated.It's known that Ca2+-Ca M is an important second messenger in signal transduction at low temperature,so we further speculated that calmodulin related genes play a regulatory role in this bioprocess.Its function can be verified through subsequent knockout experiment.