Expression Analysis Of Key Genes In Lipid Synthesis From Different Seed Oil Content Of Rapeseed (Brassica Napus L.)

Rapeseed belongs to cruciferous of Brassicaceae.It is one of the four major oil crops in China,and is also an important source of edible vegetable oil and protein in the world.The genetic characters of the oil content in rapeseed seeds were complex with the main gene and the quantitative traits of polygene.It was not only affected by the parent genotype but also by the ecological environment.Therefore,the interaction between gene and environment had a great influence on the oil content stability of rapeseed.Understanding the key genes for regulating the oil content accumulation of Brassica napus L.at the molecular level which provided an efficient way for breeding new materials with high oil content.To realize the influence of the environment in different region for the seed oil content.In this study,different cultivars(lines)of rapeseed(Brassica napus L.)were used as the research object.we measured the accumulation of oil content in the process of seed growth and development in Changsha of Hunan province.Transcriptome sequencing technology was used to explore the expression profiles of different cultivars(lines)at different developmental stages of rapeseed,and analyze the differences in expression genes between different cultivars or different stages of seed development.And further to study the expression of genes which related to the metabolism of lipid in rapeseed(Brassica napus L.)at different stages.The main findings are as follows:1.The effect of regional differences on the oil content of the same variety(line)is inconsistent.The oil content of Xiangyou15 in various regions was stable at about 42%,and it was stable and low oil content.The seed oil content of zhongyou511(ZY511)in each area was about 51%,which was stable and high oil content.The regional differences have a great influence on the oil content of Zheyou50,and oil content of the seed was between 44.5% and 50.1%,which was unstable and high oil content.2.The seed oil content of the different cultivars(Brassica napus L.)in Changsha was increased with S type.The seed oil content was accumulated gradually since 15 days,then accumulation period and reached the maximum value at 30 days.While it was gradually reduced after 45 days.The results showed that the accumulative process of seed oil content of Brassica napus L.was presented a "S" type,that based on the study of the dynamic changes of the seed oil content of different rapeseed cultivars(lines)in Changsha area.After pollination among 15 days and 30 days,it was a slow growth period,the rapid growth period was after pollination among 30 days and 40 days.At this time,the oil content of the seeds increased rapidly,after pollination between 40 days and 45 days was also a slow growth period,and 45 days after pollination Slightly lower.3.Different cultivars of rapeseed(Brassica napus L.)at different seed development periods(25d,35 d and 45d)were selected to construct 9 transcriptome sequencing library.We obtained a total of 368,535,677 clean reads,and 303,745,341 reads by mapping with the genome of rapeseed(Brassica napus L.).The differentially expressed sequences that for different developmental stages of three cultivars were 4,299,and for different cultivars of three stages were 14,781.The differentially expressed sequences were classified by GO function,including more than 40% of the biological processes,about 30% of the cell components,and more than 18% of the molecular function.The differentially expressed sequences were identified as a reference of the KEGG pathway database.The different expression sequences that for the same cultivars(lines)at different development periods could be annotated to the 74 metabolic pathways,and at three of seeds development periods can be annotated to 133 metabolic pathways.The results showed that the differentially expressed genes of the three cultivars(lines)were carried out with the development of the seeds,and most of the genes were up-regulated,such as class II heat shock protein,delt-9-acyl-lipid desaturase,3-ketoacyl-CoA thiolase and palmitoyl-acyl carrier protein thioesterase.However,the differentially expressed genes of different cultivars(lines)were obviously different at three development stages of seeds.The Xiangyou15 of low oil content compared with the ZY511 of high oil content,the number of differentially expressed genes were increased gradually with the development of seeds.And the significantly down-regulated genes are more than the significantly up-regulated genes.The Zheyou50 of relatively unstable oil content compared with the ZY511 of relatively stable oil content,the differentially expressed genes were also increased gradually with the development of seeds,which the expression of up-regulated genes were more than expression of the downregulated genes.The results indicated that the genes of related to the metabolism of fatty acids were very active in the process of lipid metabolism for rapeseed(Brassica napus L.)seeds,and the expression of related regulatory genes was increasing with the progress of lipid metabolism.When the accumulation of lipids reaches the saturation state,the oil metabolism reaches a certain dynamic equilibrium,which provides a reference for the cloning of oil metabolism and related genes.4.We used RT-qPCR to detect the expression of genes which related to lipid metabolism in different cultivars of rapeseed(Brassica napus L.).The results were as follows: the expression profiles for BnACC1,BnDGAT1,BnPDAT1,BnACP5,BnFAE1,BnADS1,BnSDP1 and BnOLEO4 were significantly different in different cultivars.The expression level of BnACC1 gene and BnDGAT1 gene were positively correlated with the accumulation of lipid at seed maturity stage.BnSDP1 gene and BnOLEO4 gene were highly expressed at 35 days after pollination,and the expression level of BnSDP1 gene increased with the increase of seed oil content.