Journal
FRONTIERS IN PLANT SCIENCE
Volume 13, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fpls.2022.854103
Keywords
soybean (Glycine max (L; ) Merr; ); diacylglycerol acyltransferase 3 (DGAT3); yeast functional complementation assay; genetic transformation of tobacco (Nicotiana benthamiana); fatty acid and TAG biosynthesis
Categories
Funding
- National Natural Science Foundation of China [31401430]
- Key Research and Development Program of Shanxi Province [201703D221002-3]
- Colleges and Universities Scientific Research Outstanding Achievement Cultivation Project of Shanxi Province
- Training Project of Research Achievements of Universities in Shanxi Province, Science and Technology Innovation of Higher Education of Shanxi Province
- Science and Technology Innovation of Higher Education of Shanxi Province [2021L112]
- Biological Breeding Engineering of Shanxi Agricultural University [YZGC101]
- Basic Research Program of Shanxi Province [20210302124170]
- 2021 Graduate Innovation Project of Shanxi Province, China [2021Y310]
- Applied Basic Research Program of Shanxi Academy of Agricultural Science [YGC2019FZ4]
- Local Science and Technology Development Project
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Diacylglycerol acyltransferases (DGAT) are key enzymes in the biosynthesis of triacylglycerol (TAG) in soybean. In this study, two members of the DGAT gene family, GmDGAT3-1 and GmDGAT3-2, were identified. GmDGAT3-2 showed higher expression in various soybean tissues and had strong enzymatic activity in TAG biosynthesis with a preference for monounsaturated fatty acids. Transgenic tobacco plants expressing GmDGAT3-2 had increased seed oil and oleic acid levels. These findings provide insights into TAG biosynthesis and its regulation in soybean.
Diacylglycerol acyltransferases (DGAT) function as the key rate-limiting enzymes in de novo biosynthesis of triacylglycerol (TAG) by transferring an acyl group from acyl-CoA to sn-3 of diacylglycerol (DAG) to form TAG. Here, two members of the type 3 DGAT gene family, GmDGAT3-1 and GmDGAT3-2, were identified from the soybean (Glycine max) genome. Both of them were predicted to encode soluble cytosolic proteins containing the typical thioredoxin-like ferredoxin domain. Quantitative PCR analysis revealed that GmDGAT3-2 expression was much higher than GmDGAT3-1's in various soybean tissues such as leaves, flowers, and seeds. Functional complementation assay using TAG-deficient yeast (Saccharomyces cerevisiae) mutant H1246 demonstrated that GmDGAT3-2 fully restored TAG biosynthesis in the yeast and preferentially incorporated monounsaturated fatty acids (MUFAs), especially oleic acid (C18:1) into TAGs. This substrate specificity was further verified by fatty-acid feeding assays and in vitro enzyme activity characterization. Notably, transgenic tobacco (Nicotiana benthamiana) data showed that heterogeneous expression of GmDGAT3-2 resulted in a significant increase in seed oil and C18:1 levels but little change in contents of protein and starch compared to the EV-transformed tobacco plants. Taken together, GmDGAT3-2 displayed a strong enzymatic activity to catalyze TAG assembly with high substrate specificity for MUFAs, particularly C18:1, playing an important role in the cytosolic pathway of TAG synthesis in soybean. The present findings provide a scientific reference for improving oil yield and FA composition in soybean through gene modification, further expanding our knowledge of TAG biosynthesis and its regulatory mechanism in oilseeds.
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