Analysis Of Physiological Response And Differentially Expressed Genes Of Temperature Stress Of Arthrospira

In order to improve the biomass of Arthrospira(Spirulina),although many scholars reported the growth mechanism of temperature stress according to the physiological and biochemical indicatorsa of Arthrospira,but the related research about transcriptome was rarely reported.Therefore,taking Arthrospira sp.TJSD091 that was isolated and purified by ourself as the object,which were conducted RNA-sequencing after 45 ? and 15 ?treatment for 24 h,through the functional annotation of differentially expressed genes,verifying significantly differentially expressed genes by qRT-PCR,and determining the physiological and biochemical indexes related at the same time,trying to fully reveal the influence on metabolic pathways of the different culture temperature,which lay the foundation of growth regulation and resistance mechanism under temperature stress.The main results are as follows:1.The contents of main fatty acid in the cell had obvious changes by temperature stress.The contents of total saturated fatty acid and stearic acid increased when the Arthrospira sp.TJSD091 grew in 45 ?,which helps to maintain stability of membrane;The content of unsaturated fatty acid,especially the alpha linolenic acid,increased significantly in 15 ?,enhancing the fluidity of membrane in order to maintain normal physiological metabolic activity in the cell.Transcriptomics data analysis showed that the reduction in the expression of ?9 des in 45 ? increased the amount of stearic acid;the gene expressions of3-acyl-[acyl carrier protein]-reductase,?9 des and ?12 des increased in 15 ?,therefore the synthesis of unsaturated fatty acid increased.2.The contents of photosynthetic pigments,such as Chl a,PC and APC,were also significantly reduced by temperature stress,photosynthesis was affected,and the relative growth rate decreased.The content of Car continued to rise in 45 ?,would not only help photosynthesis in high temperature,also effectively remove reactive oxygen free radicals to prevent peroxidation in the cell.3.Compared with the 35 ?,the numbers of total differentially expressed genes in45 ?/15 ? were 366/614 respectively,the numbers of up/down-regulation were respectively 192/174 in 45 ? and 365/249 in 15 ?.The differentially expressed genes were significantly enriched in photophosphorylation and oxidative phosphorylation in temperature stress.In addition,the significantly enriched pathways also included ribosomes and HIF-1 signals in 45 ? and nitrogen metabolism in 15 ? respectively.4.Some changes of gene expression in the cell were consistent in 45 ? and 15 ?,such as PS? reaction center D1 protein(psbA)and D2 protein(psbD)increased theexpression in order to maintain the correct conformation of PS?.Pigment protein cp43(psbC)gene expression decreased,the synthesis process was restrained,affecting the efficiency of capture and transmission light energy,eventually reducing light reaction efficiency.And as the NADH dehydrogenase in oxidative phosphorylation,the gene expression of protein subunits NdhD increased,affecting the NADH dehydrogenation reaction,leading to insufficient energy,which affected the growth of algae.