| Plant oils play an essential role in the human diets and have wide utilization for industrial raw materials,they were also considered as the potential biological energy.G.max,G.hirsutum,B.napus,S.indicum were main oil crops,oil content of them were 20%.30%,40%and 50%successively,meanwhile,there were specificity of the fatty acid composition in them.Recently,a large number of studies of Z.mays,G.max,G.hirsutum,B.napus,S.indicum etc.involved in lipid related genes identification or functional cloning using molecular methods were accomplished,but rare of which with a view to systematically research of lipid metabolism,due to oil content and fatty acid composition were complicated quantitative traits regulated by population,environment and other factors.For the sake of revealing differentiation about oil metabolism iin above crops,in present study,we initially have obtained four kinds of oil crops for transcriptome analysis using RNA-sequencing technology,each oilseed material provided five different development stages which was divided into o,10,20,30,40 DPA and three biological replications were used for RNA libraries preparation.Additionally,we searched RNA-seq data of Z.mays for control.It is necessary to mined critical genes involved in oil synthesis metabolism pathways and made systematic classification for them.Finally,some homologous genes involved in key enzymes were obtained within these two approaches.Better understanding of lipid biosynthesis and its regulation in both model and non-model plants is likely to be one key to improve the content and composition of oils used for food or other applications.The main results are as follows:1.The total oil contents shows negative correlation with correspongding total protein cotents in above four oil crops.Oil contents of them were 20%,30%,40%and 50%successively in G.max,G.hirsuzurm,B.napus,S.indicum.The palmitic acid,oleic acid,linoleic acid and linolenic acid accounted large proportion in all five crops,including Z.wmays,total proportion of them were greater than 80%;we also found that fatty acids composition displayed species specificity,such as higher level of erucic acid in B.napus and a kind of unknown fatty acid type may from C22:l to C24:0 was detected in G.hirsutum.Morever,G.hirsutum and G.max contained higher linoleic acid than other fatty acid components on their own,oleic acid were next.2.We identified lipid related genes in five crops based on A.thaliana database of lipid metabolism and sort out 1177,1530,2096,2652,718 genes in G.max,G.hirsutum,B.napus,S.indicum,respectively,which accounted for 2.62-2.97%of their whole predicted genes,it revealed that total fatty acid contents have no clear correlation with lipid related genes.Maxmum amount of lipid related genes derived from fatty acid synthesis&elongation,wax or sphingolipid biosynthesis pathways.Oppositely,the fewest proportion of that exist in the mitochondrial lipid synthesis.Meanwhile,almost same proportion of orthologous genes were served in fatty acid synthesis,elongation and triacylglycerol pathways.However,we obtained TRs involved in 24 enzymes of fatty acid synthesis,saturated,elongation,TAG synthesis,oil storage pathways in further analysis for characteristic gene structure in five crops.Clustering genes existed in four main crops were significant more than Z.mays,of these,gene members of LTP family and CYP450 family were extended remarkably.3.Expression patterns analysis for lipid related genes within different development stages in five crops.From transcriptome sequencing of all samples,we totally got 560.93Gb raw data and remaied 492.05Gb after filtering,83.20%reads with high-quality were used mapping to reference genome,the average mapping rate reached 87.58%.We mined differentially expressed genes(DEGs)within adjacent development stages of each material and then constructed genomic functional categories in five oil crops upon the unified standards respectively for pathway enrichment.The major results were concluded as several points:metabolic patterns of Z.mays(monocotyledon)was differed with four dicotyledon crops,DEGs of former were mainly classified into amino acid metabolism and less belonged to lipid metabolism,but opposite performance were found in other dicotyledon crops.Additonally,we screened a large number of genes of TAG pathway in dicotyledon crops,while non-obtained in Z.mays;DEGs of glycolysis,FAs synthesis etc.pathways were up-regulated in preliminary development stage(0-20 dpa)and TAG related DEGs were performanced in 30-40dpa,it revealed that FAs synthesis slowed down gradually and forward to the oil accumulation within seeds maturity.From inspection of global expressed levels,which of FAs&TAG showed rising former and falling later in five crops except Z.mays&G.rrmax,unlike actively up-expressed in S.indicum.Especially emphasis that expressed levels of genes related to oil body storage in five crops were accordance with their total oil contents.Oleosin related genes were upregulated dramatically from 20dpa on,suggesting that oil seed begin to accumulate a lot of fatty acid at this stage.4.In addition,we had constructed a comprehensive diagram of lipid metabolisn matched the expression profiles of five kinds of oil crops.Expressional pattern,phylogenesis analysis and gene structural comparison of the orthologous genes related to SAD,FAD were explored for mining metabolic rules in oil crops.Results indicate that linoleic acid and linolenic acid contents in five kinds of oilseeds positively correlated,with oleic acid content had a negative correlation with their summation,it matches the changes in the expression of FAD and SAD genes.5.Analysis for transcriptional regulatory network of lipid netabolism.Many TFs play an crucial role in the regulation of lipid synthesis and metabolism,for instance,the expression level of B3 domain family(LEC1,WRI,FUS3,ABI3,ABI4)increased gradually during seed development,and significantly higher expressed in high oil content oilseeds,they were essential for lipid accumulation,whereas inhibitor HSI2/VAL1 and HSL1/VAL2 showed a reversely expressed trend.In short,by comparing the lipid gene expression of the four different oil content crops(G.max,G.hirsutum,B.napus,S.indicum)during the seed formation process,our study provides valuable scientific basis for revealing the molecular mechanism of their difference in oil content and provides vital candidate genes for molecular genetic improvement of oil contents and compositions of these four oil crops. |
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