Improving The Seed Oil Content And Quality By DGAT1 And FAD2-1 Gene Regulation In Cotton

With the development of China's economy and the improvement of people's living standards,the demand for vegetable oil has increased year by year,and the relationship between supply and demand is tense.At present,most vegetable oils are imported from abroad.As the main fiber crop,cotton has a large planting area in China,and the total yield of cottonseed as a by-product is huge.Cottonseed is rich in protein,vitamin E and unsaturated fatty acid.Cottonseed is rich in protein,vitamin E and unsaturated fatty acids.It is of great significance to improve the oil content of cottonseed and the fatty acid composition of cottonseed oil for increasing the yield and quality of vegetable oil in China if the yield and quality of cotton fiber are not affected and the cultivated land area is not increased..Diacylglycerol acyltransferase?DGAT?is the last step reaction enzyme in the process of triglyceride?TAG?synthesis in vivo,and is also the rate-limiting enzyme;Studies have shown that overexpression of DGAT can increase the accumulation of oil in plants.In this study,the GhDGAT1 transgenic cotton progeny?T₃^T₅?obtained in our laboratory were planted for many years to verify the stability of expression,in order to obtain homozygous and stable transgenic high oil cotton germplasm.According to the synthesis mechanism of different fatty acids,GhFAD2-1,a key gene for controlling the conversion of oleic acid to linoleic acid,was selected to construct RNAi vector and transformed into cotton,in order to create high oleic acid low linoleic acid cotton germplasm,and verify its genetic stability by multi-point planting its offspring?T₂^T₄?for many years.The main results are as follows:?1?From 7?GP promoter transgenic lines??GP-GhDGAT1?and 4 35S promoter transgenic lines?35S-GhDGAT1?,2 single copy transformation events AGP1 and AGP2were screened,all of which were?GP-GhDGAT line.The expression levels,enzyme activities and triglyceride?TAG?content of AGP1 and AGP2 were determined to be higher than those of the negative control.Through multi-year multi-point determination of seed oil content of these two lines,the oil content was higher than that of the negative control,and it could be stably inherited to the offspring.Compared with the control,the two transgenic lines of T₅ generation AGP1 and AGP2 planted in Ezhou,Hubei Province increased by 3.55%and 3.61%respectively?P<0.01?.At the same time,the agronomic traits,fiber quality and photosynthetic characteristics of the two lines were not significantly different from the control plants.?2?The RNAi vector of GhFAD2-1 gene was constructed and genetically transformed on cotton.A total of 16 GhFAD2-1 transgene positive lines were obtained.Three transgenic lines with high oleic acid and low linoleic acid,FDA-5,FDA-11 and FDA-14,were screened in T₂ generation.?3?Through the planting and fatty acid determination of FAD-5,FAD-11,FAD-14lines for many years at multiple sites?T₂^T₄?,the phenotypes of FAD-5 and FAD-11 can be stably inherited to the offspring.According to the results of Southern hybridization,FAD-5 was a double copy line and FAD-11 was a three copy line.In 2018,the oleic acid of the two transgenic lines of T₄ planted in Wuhan,Hubei Province increased from 18.18%and 18.86%to 58.92%and 46.88%,respectively,and the linoleic acid content from 51.54%and 51.19%were reduced to 15.27%and 26.44%.Compared with the control plants,there was no significant difference in agronomic traits,fiber quality and photosynthetic characteristics of the transgenic lines.