HighlightArabidopsis glycerol-3-phosphate acyltransferase 9 (GPAT9) is an sn-1 specific acyl-CoA:GPAT that contributes to intracellular glycerolipid biosynthesis in seeds, developing leaves and pollen grains, but not to extracellular glycerolipid biosynthesis.

Edited by George M. Carman Polyunsaturated fatty acids (PUFAs) such as ␣-linolenic acid (ALA, 18:3⌬ 9cis,12cis,15cis ) have high nutritional and industrial values. In oilseed crops, PUFAs are synthesized on phosphatidylcholine (PC) and accumulated in triacylglycerol (TAG). Therefore, exploring the mechanisms that route PC-derived PUFA to TAG is essential for understanding and improving PUFA production. The seed oil of flax (Linum usitatissimum) is enriched in ALA, and this plant has many lipid biosynthetic enzymes that prefer ALA-containing substrates. In this study, using membrane yeast two-hybrid and bimolecular fluorescence complementation assays, we probed recombinant flax transferase enzymes, previously shown to contribute to PUFA enrichment of TAG, for physical interactions with each other under in vivo conditions. We found that diacylglycerol acyltransferases, which catalyze the final reaction in acyl-CoA-dependent TAG biosynthesis, interact with the acyl-editing enzymes phosphatidylcholine: diacylglycerol cholinephosphotransferase, and lysophosphatidylcholine acyltransferase. Physical interactions among the acyl-editing enzymes were also identified. These findings reveal the presence of an assembly of interacting transferases that may facilitate the channeling of PUFA from PC to TAG in flax and possibly also in other oleaginous plants that produce seeds enriched in PC-modified fatty acids.Seed oils of flax (Linum usitatissimum), which are predominantly in the form of triacylglycerol (TAG), 2 contain 45 to 65%

Acyl-lipids such as intracellular phospholipids, galactolipids, sphingolipids, and surface lipids play a crucial role in plant cells by serving as major components of cellular membranes, seed storage oils, and extracellular lipids such as cutin and suberin. Plant lipids are also widely used to make food, renewable biomaterials, and fuels. As such, enormous efforts have been made to uncover the specific roles of different genes and enzymes involved in lipid biosynthetic pathways over the last few decades. sn-Glycerol-3-phosphate acyltransferases (GPAT) are a group of important enzymes catalyzing the acylation of sn-glycerol-3-phosphate at the sn-1 or sn-2 position to produce lysophosphatidic acids. This reaction constitutes the first step of storage-lipid assembly and is also important in polar- and extracellular-lipid biosynthesis. Ten GPAT have been identified in Arabidopsis, and many homologs have also been reported in other plant species. These enzymes differentially localize to plastids, mitochondria, and the endoplasmic reticulum, where they have different biological functions, resulting in distinct metabolic fate(s) for lysophosphatidic acid. Although studies in recent years have led to new discoveries about plant GPAT, many gaps still exist in our understanding of this group of enzymes. In this article, we highlight current biochemical and molecular knowledge regarding plant GPAT, and also discuss deficiencies in our understanding of their functions in the context of plant acyl-lipid biosynthesis.

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A continuous rise in demand for vegetable oils, which comprise mainly the storage lipid triacylglycerol, is fueling a surge in research efforts to increase seed oil content and improve fatty acid composition in oilseed crops. Progress in this area has been achieved using both conventional breeding and transgenic approaches to date. However, further advancements using traditional breeding methods will be complicated by the polyploid nature of many oilseed crops and associated time constraints, while public perception and the prohibitive cost of regulatory processes hinders the commercialization of transgenic oilseed crops. As such, genome editing using CRISPR/Cas is emerging as a breakthrough breeding tool that could provide a platform to keep pace with escalating demand while potentially minimizing regulatory burden. In this review, we discuss the technology itself and progress that has been made thus far with respect to its use in oilseed crops to improve seed oil content and quality. Furthermore, we examine a number of genes that may provide ideal targets for genome editing in this context, as well as new CRISPR-related tools that have the potential to be applied to oilseed plants and may allow additional gains to be made in the future.