Abstract：Diacylglycerol acyltransferase (DGAT) widely existing in organisms plays an important role in the synthesis of triacylglycerol. In peanuts (Arachis hypogaea), two copies of AhDGAT3 gene (AhDGAT3A and AhDGAT3B) exist in peanut genome, and have been cloned in our previous research. In order to study the functions of the acyltransferase during lipid accumulation, and explore the breeding strategy of increasing peanut oil content and optimizing the fatty acids composition, two types of plant overexpression vectors driven separately by Cauliflower mosaic virus (CaMV) 35S constitutive promoter and the seed-specific promoter from soybean agglutinin Lectin gene were constructed. Through peanut genetic transformation and successive screening for the transgenic plants of T0~T4 generation by sequencing the PCR products of target gene, the homozygous transgenic lines carrying the 4 constructs stably in genetics were developed. On the major agronomic characters, such as flowering times, the quantity of branches and disease resistance, there were no significant differences between the transgenic lines and the control. The detail oil contents and fatty acid compositions of the transgenic seeds were determined by near infrared spectrum (NIR) and gas chromatography (GC). It was found that compared with FH1, the contents of the protein and the oil in transgenic seeds were similar; however, the contents of C18 fatty acids change significantly in comparison with the other fatty acids, stearic acid increased by 11.84%~22.95%, oleic acid increased by 5.13%~21.26%, while linoleic acid decreased by 3.87%~31.18%, and correspondingly, the ratio of oleic acid and linoleic acid (O/L) increased by 5.01%~76.19% compared to the control. The results suggested that AhDGAT3 maybe prefer to oleoyl as the substrate and cause more oleic acid accumulating in transgenic peanut seeds. In this work, it was also found that the improvement of O/L is higher in transgenic peanuts with AhDGAT3B than that in AhDGAT3A overexpression lines, inferring that AhDGAT3B had stronger biological functions. In addition, the changes of O/L in transgenic peanut seeds with different promoter were varied greatly, because the CaMV 35S promoter has higher expression level than Lectin promoter. This research may provide the theoretical foundation for the improvement of peanut oil quality.
