Oil Dynamic Accumulation And Expression Differences Of Key Genes In Developing Seed In Brassica Napus L.

The main purpose of rapeseed is providing seed oil for human,so the seed oil content seriously affects it's production efficiency.At present,it is urgent to improve the yield of rapeseed by increasing the oil content of seeds to meet the market demand at home and abroad for our situation of rapeseed production,which causes that high oil content breeding of rapeseed become one of the main objectives of breeders.But now,the study on the oil biosynthesis and it's molecular mechanism is not fully understood,and we know little on the oil accumulation dynamic and the expression differences of related genes in different oil content lines of Brassica napus L..In order to analysis the differences of oil accumulation dynamics,four high oil content lines and three low oil content lines of Brasscia napus L.,which have different genetic backgrounds,were used as the experimental materials,to mensurate the seed oil content in 7 periods by residual method.At the same time,the expression levels and patterns of significant genes,which influenced oil biosynthesis,analyzed by quantitative real-time PCR technology in high oil lines and low oil lines' developing seeds,to investigate the expression differences of 5 enzyme encoding genes(ACCase?DGAT1?DGAT2?Fat A?Fat B)and 1 transcription factor WRI1.The ultimate goal is to provide theoretical basis for the oil content's genetic improvement and high oil content breeding of rapeseed,promoting the germplasm innovation of rapeseed and it's breeding of new varieties.The main results of this study are as follows:1.The analysis of oil accumulation dynamic and the differences between high oil content lines and low oil content lines showed that:(1)The law of oil accumulation in the developing seeds of 4 high oil content lines,with different genetic backgrounds,was consistent basically.In the early stage of seed development,the oil accumulation was slow,and the oil content only accounted for 13.8%~21.4% of mature seeds at 25 days after flowering.The rapid period of oil accumulation was 26~35 days after flowering,and the oil content accounted for 82.9%~94.5% of mature seeds at 35 days after flowering.After that,the accumulation speed of seed oil was slowed down,at maturity the oil content reached the maximum value.As a trait,the oil content in high oil content lines had the same performance,and it's formation is closely related to the duration of rapid accumulation period.(2)The most significant period of difference in oil accumulation between high oil content lines and low oil content lines was 25~35 days after flowering,when the oil content in seeds was rapid accumulating.The oil accumulation's rate in high oil content lines was significantly higher than that in low oil content lines,which,to a great extent,determined the differences of the oil content in different rapeseed lines.After that,the amount of oil accumulation became small in 36~45 days after flowering,and the high oil content lines showed positive accumulation,while the low oil content lines showed negative accumulation,which was also one of the important reasons for the differences of final oil content between high oil content lines and low oil content lines.2.The expression analysis of key genes influenced the oil biosynthesis in high oil content lines and low oil content lines showed that:(1)In high oil content lines,the expression patterns of ACCase,Fat A and WRI1 were similar,indicated that the expression of the main genes in high oil content lines with different genetic backgrounds had a good consistency,and the expression dynamic of Fat A and WRI1 was basically the same as the oil accumulation dynamic.(2)Between high oil content lines and low oil content lines,there were significant differences in the expression patterns or expression levels of most of genes,and not all genes in high oil content lines had high expression levels.Overall,the expression levels of ACCase and Fat A were obviously higher in high oil content lines than that in low oil content lines during seed development,which closely associated with the formation of high oil content,to a certain extent,played a decisive role in the formation of high oil content in rape seeds.The DGAT2 had no decisive effect on the formation of the oil content,but it mainly played a role in the latter stage of seed development,because it could affected the oil transformation in that time and indirectly influenced the oil content became high or low.The expression levels of WRI1 and Fat B in low oil content lines were significant higher than that in high oil content lines,thus they had no positive effect on the oil accumulation,not the direct factors of it.3.Correlation analysis between key genes in oil biosynthesis and the oil content showed that,in low oil content lines,the relationship between the genes' expression and the oil content in seeds had same performance,it's oil accumulation mechanism was single;while the relationship between some genes' expression and the oil content in seeds in high oil content lines were inconsistent,indicated that there were a variety of oil formation mechanisms in high oil content lines,which oil formation in seeds was more complex than that in low oil content lines.The genes of Fat B and WRI1 showed negative correlation with the oil content,so that their high expression in seeds had no positive effect on oil accumulation,but played an important role in regulation and control on other genes.