Evolution and Characterization of Acetyl Coenzyme A: Diacylglycerol Acyltransferase Genes in Cotton Identify the Roles of GhDGAT3D in Oil Biosynthesis and Fatty Acid Composition

Abstract

Cottonseed oil is rich in unsaturated fatty acids (UFAs) and serves as an edible oil in human nutrition. Reports suggest that acyl-coenzyme A: diacylglycerol acyltransferases (DGAT) and wax ester synthase/DGAT (WSD1) genes encode a key group of enzymes that catalyze the final step for triacylglycerol biosynthesis and enable an important rate-limiting process. However, their roles in oil biosynthesis and the fatty acid profile of cotton seed are poorly understood. Therefore, the aim of this study was to identify and characterize DGAT and WSD1 genes in cotton plants and examine their roles in oil biosynthesis, the fatty acid profile of cotton seeds, and abiotic stress responses. In this study, 36 GhDGAT and GhWSD1 genes were identified in upland cotton (G. hirsutum) and found to be clustered into four groups: GhDGAT1, GhDGAT2, GhDGAT3, and GhWSD1. Gene structure and domain analyses showed that the GhDGAT and GhWSD1 genes in each group are highly conserved. Gene synteny analysis indicated that segmental and tandem duplication events occurred frequently during cotton evolution. Expression analysis revealed that GhDGAT and GhWSD1 genes function widely in cotton development and stress responses; moreover, several environmental stress and hormone response-related cis-elements were detected in the GhDGAT and GhWSD1 promoter regions. The predicted target transcription factors and miRNAs imply an extensive role of GhDGAT and GhWSD1 genes in stress responses. Increases in GhDGAT3 gene expression with increases in cottonseed oil accumulation were observed. Transformation study results showed that there was an increase in C18:1 content and a decrease in C18:2 and C18:3 contents in seeds of Arabidopsis transgenic plants overexpressing GhDGAT3D compared with that of control plants. Overall, these findings contributed to the understanding of the functions of GhDGAT and GhWSD1 genes in upland cotton, providing basic information for further research.

Comparative genomics points to tandem duplications of SAD gene clusters as drivers of increased α‐linolenic (ω‐3) content in S. hispanica seeds

“…The S. hispanica genome contains an increased number of tandem‐duplicated SAD genes that are upregulated in reproductive tissues, leading to abundant production of PUFAs. This may represent an adaptive response to environmental stress, as seen in other plants (J. Chen et al., 2023; Feng et al., 2017; Zhao et al., 2021). The ShSAD2 and ShSAD7 genes in S. hispanica are overexpressed in response to cold stress (Xue et al., 2023).…”

“…In S. indicum , a combination of lipid transfer gene family expansion due to tandem duplication and contraction of lipid degradation genes was identified as driving the high accumulation of FAs in seeds (L. Wang et al., 2014). The highly conserved domains in segmental and tandem duplicated wax ester synthase ( WSD1 ) and DGAT genes in Gossypium hirsutum (cotton) were related to a rate‐limiting process during high unsaturated FAs accumulation in seeds (Zhao et al., 2021). The expansion of GmFAD2 genes in Glycine max (soybean) (Lakhssassi et al., 2021) and OeB3 genes in Olea europaea (olive) (Qu et al., 2023) was associated with tandem duplications.…”

“…This may represent an adaptive response to environmental stress, as seen in other plants (J. Chen et al, 2023;Feng et al, 2017;Zhao et al, 2021). The ShSAD2 and ShSAD7 genes in S. hispanica are overexpressed in response to cold stress (Xue et al, 2023).…”

Different acyl-CoA:diacylglycerol acyltransferases vary widely in function, and a targeted amino acid substitution enhances oil accumulation

“…DGAT2 from some species is reported to contribute to the accumulation of unusual fatty acids such as a hydroxy fatty acid (ricinoleic acid) in castor bean (Ricinus communis) (Burgal et al, 2008;Cagliari et al, 2010;Kroon et al, 2006;Regmi et al, 2020;Shockey et al, 2019;Troncoso-Ponce et al, 2011), a conjugated fatty acid (αeleostearic acid) in tung tree (Vernicia fordii) (Shockey et al, 2006), and an epoxy fatty acid (vernolic acid) in Vernonia (Vernonia galamensis) (Li et al, 2010b). DGAT1 and DGAT2 are ER membrane-bound, whereas DGAT3 is a soluble cytoplasmic enzyme identified in peanuts (Arachis hypogaea) (Saha et al, 2006), Arabidopsis thaliana (Hernandez et al, 2012), and upland cotton (Gossypium hirsutum) (Zhao et al, 2021). A fourth type of DGAT has a sequence similar to DGAT2 and has both wax ester synthase (WS) and DGAT activity (WS / DGAT) (Kalscheuer and Steinbuchel, 2003;King et al, 2007;Li et al, 2008;Rosli et al, 2018;Xu et al, 2021).…”

“…A fourth type of DGAT has a sequence similar to DGAT2 and has both wax ester synthase (WS) and DGAT activity (WS / DGAT) (Kalscheuer and Steinbuchel, 2003;King et al, 2007;Li et al, 2008;Rosli et al, 2018;Xu et al, 2021). The most common DGAT is type 1 (DGAT1), which contributes to most of the TAG synthesis in higher plants (Chen et al, 2016;Sanjaya et al, 2013;Xu et al, 2018a), but DGAT2 plays a major role in castor bean (Burgal et al, 2008;Kroon et al, 2006;Troncoso-Ponce et al, 2011) and tung tree (Shockey et al, 2006), and DGAT3 is expressed highly in upland cotton (Zhao et al, 2021). Many studies have reported that increased expression of the DGAT1 gene increases oil content (Andrianov et al, 2010;Lardizabal et al, 2008;Rao and Hildebrand, 2009;Taylor et al, 2009).…”