The review, led by researchers at Sun Yat-sen University in collaboration with the University of Almería and the Swedish University of Agricultural Sciences, systematically surveys more than a decade of progress in plant lipid metabolic engineering. Its central argument is that cereals, despite their naturally low seed oil content of roughly 2 to 4 percent of grain dry weight, possess the complete lipid biosynthetic machinery, the agronomic infrastructure and the transformation toolkits needed to become scalable chassis for lipid biomanufacturing. What has been missing until recently is the ability to redirect their carbon flow, and that is precisely what modern genome editing and multigene stacking now make possible.

At the heart of the engineering challenge lies a well-characterized metabolic network. De novo fatty acid synthesis begins in the plastid, where acetyl-CoA is carboxylated by acetyl-CoA carboxylase, the rate-limiting enzyme of the pathway, to generate malonyl-CoA. The fatty acid synthase complex then elongates the carbon chain in two-carbon increments, typically producing C16 and C18 fatty acids that are released by thioesterases and exported to the cytosol. There, long-chain acyl-CoA synthetases activate them into the acyl-CoA pool that feeds triacylglycerol assembly in the endoplasmic reticulum, proceeding through the Kennedy pathway or the acyl-CoA-independent PDAT route. Phosphatidylcholine acts as a central hub in this network, hosting desaturation reactions catalyzed by FAD2 and FAD3 and shuttling modified fatty acids back and forth through acyl editing mediated by LPCAT.

Engineering this network in cereals has followed what the authors describe as a push-pull-package-protect strategy. The push component boosts fatty acid synthesis in the plastid, often by overexpressing the transcription factor WRINKLED1, a master regulator that activates genes for glycolysis and fatty acid production. The pull component drives fatty acids into triacylglycerol through diacylglycerol acyltransferases such as DGAT1. The package component sequesters the resulting oil into stable oil bodies, frequently by enhancing oleosin proteins that coat and stabilize lipid droplets. The protect component preserves oil body integrity and limits turnover. In rice, combining all four modules by co-expressing Arabidopsis WRI1, DGAT1, PDAT and oleosin increased seed triacylglycerol content by 26 percent and raised total oil by 70 percent in seeds and 22.5 percent in leaves.

The most dramatic demonstration of carbon reallocation in a cereal came from a recent rice study highlighted in the review. By expressing Arabidopsis DGAT1 specifically in the endosperm under the Glb1 promoter, while simultaneously using CRISPR-Cas9 to knock out AGPL2, a rate-limiting gene in starch biosynthesis, and MTSSB1, a regulator of aleurone layer thickness, researchers pushed grain oil content from 2.33 percent to 11.72 percent of dry weight, a more than fivefold increase achieved in an elite cultivar without major agronomic penalties. In maize, embryo-preferred expression of the native ZmWRI1 raised seed oil by 30.6 percent without harming vegetative growth, whereas overexpression of ZmLEC1, which acts upstream of WRI1, boosted oil by 48.7 percent but caused germination and developmental defects, underscoring the importance of tissue-specific and carefully balanced regulation.

Beyond simply making more oil, engineers are now introducing entirely foreign lipid products. The flagship target is the very-long-chain omega-3 polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid, the compounds that make oily fish so nutritionally prized. Humans convert the plant-derived precursor alpha-linolenic acid into EPA and DHA very inefficiently, and marine fish stocks are under pressure, so plant-based sources are urgently needed. In oilseed crops such as Camelina sativa and canola, heterologous pathways assembled from marine algal and fungal genes have already achieved seed oils containing up to 19 percent combined EPA and DHA, and Nuseed’s omega-3 canola has reached commercial aquafeed markets. Cereals are catching up: in maize, introduction of an alternative delta-8 desaturation pathway using genes from Isochrysis galbana, Euglena gracilis and Mortierella alpina produced EPA at nearly 2 percent of total leaf fatty acids, a proof of concept that grain-targeted versions could follow.

Rice has taken a different route toward omega-3 enrichment, focusing first on boosting the precursor alpha-linolenic acid. Endosperm-specific overexpression of omega-3 desaturase genes from soybean and rice raised seed ALA content from 0.36 to as much as 10.06 milligrams per gram, roughly a 28-fold increase and enough to meet most daily dietary requirements. More recently, an intragenic approach using only the rice’s own FAD3 gene under an endosperm-specific promoter increased ALA nearly 15-fold without introducing any foreign DNA, potentially easing biosafety and regulatory concerns. Feeding trials in rats showed that consuming this enriched rice elevated ALA, EPA and DHA levels in serum and brain tissue, offering a glimpse of staple-food biofortification in action.

The review also charts progress on two industrial targets. Wax esters, the neutral lipids that made sperm whale oil and jojoba oil so valuable for lubricants and cosmetics, can now be produced in plants by co-expressing a fatty acyl reductase and a wax synthase. Transgenic Camelina lines have accumulated wax esters exceeding 60 percent of seed oil, and enzyme selection, oleosin-mediated targeting to lipid droplets and fusion protein design have pushed yields in Arabidopsis to over 100 milligrams per gram of seed. Insect sex pheromones represent a third frontier. Roughly three-quarters of lepidopteran sex pheromones are C10 to C18 fatty alcohols, aldehydes or acetates, and plants can be engineered to make their fatty acid precursors using desaturases, elongases and reductases borrowed from insects. Engineered Camelina accumulating pheromone precursors at more than 20 percent of seed fatty acids yielded blends that matched synthetic pheromones in field trials against the diamondback moth, and tunable CRISPR-based activation systems in Nicotiana benthamiana now allow programmable, high-yield de novo pheromone biosynthesis.

Why choose cereals at all when oilseeds are further along? The review’s comparative analysis points to scale and infrastructure. Cereals occupy vast cultivation areas, benefit from mature supply chains, harvesting systems and processing networks, and produce enormous vegetative biomass that could host industrial lipid production without competing with food uses in the grain. Rice is currently the most tractable cereal for transformation and editing, wheat remains recalcitrant although new haploid-embryo systems are changing that, and maize sits in between, with particle bombardment still widely used because Agrobacterium transformation is technically difficult. The design-build-test-learn cycle of synthetic biology, combined with multi-omics profiling, promoter engineering and iterative optimization, is expected to accelerate the identification of rate-limiting steps and tissue-specific regulatory elements in all three crops.

Significant obstacles remain. Transformation efficiency varies widely by genotype, stable multigene expression is technically demanding, and redirecting carbon away from starch can trigger pleiotropic effects including dwarfism, reduced fertility and impaired seed development, as seen in some engineered sorghum lines. Regulatory frameworks for genetically modified staple foods, particularly in the European Union, add another layer of complexity, although the authors note a gradual global shift toward more enabling policies. Still, the trajectory is clear: with omega-3 oilseeds already commercialized, wax ester and pheromone platforms advancing through field trials, and cereal oil contents now being pushed fivefold higher, the prospect of fields of rice and maize quietly manufacturing fish oils, industrial lubricants and pest-control chemicals is moving from speculation toward engineering reality, positioning the world’s oldest crops at the frontier of the emerging bio-based economy.

Subject of Research: Metabolic engineering of cereal crops for sustainable production of high-value lipids including omega-3 fatty acids, wax esters and insect sex pheromones

Article Title: Metabolic engineering of cereal lipids: from omega-3 fatty acids to wax esters and pheromones

Article References: Li, M.-T., Lin, J.-T., García-Caparros, P., Zhu, L.-H., Yao, N., & Xia, Y.-H. (2026). Metabolic engineering of cereal lipids: from omega-3 fatty acids to wax esters and pheromones. Advanced Biotechnology, 4(3), Article 28. https://doi.org/10.1007/s44307-026-00124-9

Image Credits: AI Generated

DOI: 10.1007/s44307-026-00124-9

Keywords: metabolic engineering, cereals, omega-3 fatty acids, EPA, DHA, wax esters, insect pheromones, rice, maize, wheat, synthetic biology, seed oil