Expression And Function Analysis Of Type 1 Diacylglycerol Acyltransferase (GmDGAT1A) In Soybean

Soybean (Glycine max) is an important oil crop worldwide. It is always an active research field in genetic improvement of soybean to analyze seed oil accumulation mechanism and breed new varieties with seeds rich in both oil and protein storages. Triacylglycerol (TAG) is the main storage form of seed oil. Diacylglycerol acyltransferase (DGAT) is a key enzyme to function at the last step of the acylation reaction of glycerol to form TAG. It is poorly understood regarding soybean DGAT's function s in seed oil accumulation and its developmental regulation mechanism. In this paper, the biological function of soybean DGAT gene (GmDGATIA) was characterized by gene expressionanalysis and genetic transformation. This would provide new knowledge for the comprehensive understanding of the accumulation mechanism of soybean oil and its regulation network. The main results are listed as the followings:(1) The gene expression analysis by quantitative real-time PCR showed that GmDGATIA was expressed in soybean roots, stems, leaves and flowers, with much high amount in young seeds. The expression peak appeared at stage 3 in soybean developing seeds.(2) Dynamic analysis of seed oil content demonstrated that the rapid accumulation of oil occurred from stage 3 to stage 4, and then followed by slowly increase in seed development.(3) Comparison between the dynamic changes of GmDGATIA expression and seed oil accumulation in seed development indicated that the rapid increase of GmDGAT1A expression was closely related to the fast enhancement of seed oil (TAG) content, suggesting that the GmDGATIA gene plays an important role in soybean seed oil synthesis and accumulation.(4) The GmDGATIA seed-specific expression vector was successfully constructed, which provided a necessary recombinant DNA element for characterization of GmDGATlA's biological functions by developing GmDGAT1A-overexpressed transgenic lines.(5) The soybean variety 'Jack' was used as transgenic acceptor. An optimized transformation system was developed using gene gun method and soybean somatic embryogenesis. The molecular detection of the positive transformants demonstrated that genetic transformation was successful. The transgenic lines of seed-specific expression of GmDGAT1A were finally developed.(6) The phenotypic assays in soybean GmDGATIA transformants revealed that seed-specific expression of GmDGATIA was increased by 1.8% compared with the non-transformed plants. The content of protein was not decreased. The germination characteristics of the seeds showed no change compared to the control plants.This paper proves that the GmDGATIA has spatio-temporal expression patterns, GmDGATIA plays an important role in the accumulation of soybean seed oil. Seed-specific overexpression of GmDGATIA could promote the accumulation of seed oil without negative effects on protein storage, leading to break of the negative linkage between seed oil and protein content phenotypes.