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Diacylglycerol acyl-transferase (DGAT) and cysteine oleosin (CO) expression confers a novel carbon sink (of encapsulated lipid droplets) in leaves of Lolium perenne and has been shown to increase photosynthesis and biomass. However, the physiological mechanism by which DGAT + CO increases photosynthesis remains unresolved. To evaluate the relationship between sink strength and photosynthesis, we examined fatty acids (FA), water-soluble carbohydrates (WSC), gas exchange parameters and leaf nitrogen for multiple DGAT + CO lines varying in transgene accumulation. To identify the physiological traits which deliver increased photosynthesis, we assessed two important determinants of photosynthetic efficiency, CO 2 conductance from atmosphere to chloroplast, and nitrogen partitioning between different photosynthetic and non-photosynthetic pools. We found that DGAT + CO accumulation increased FA at the expense of WSC in leaves of L. perenne and for those lines with a significant reduction in WSC, we also observed an increase in photosynthesis and photosynthetic nitrogen use efficiency. DGAT + CO L. perenne displayed no change in rubisco content or V cmax but did exhibit a significant increase in specific leaf area (SLA), stomatal and mesophyll conductance, and leaf nitrogen allocated to photosynthetic electron transport. Collectively, we showed that increased carbon demand via DGAT+CO lipid sink accumulation can induce leaf-level changes in L. perenne which deliver increased rates of photosynthesis and growth. Carbon sinks engineered within photosynthetic cells provide a promising new strategy for increasing photosynthesis and crop productivity.

Oil bodies (OBs) are ubiquitous dynamic organelles found in plant seeds. They have attracted increasing attention recently because of their important roles in plant physiology. First, the neutral lipids stored within these organelles serve as an initial, essential source of energy and carbon for seed germination and post-germinative growth of the seedlings. Secondly, they are involved in many other cellular processes such as stress responses, lipid metabolism, organ development, and hormone signaling. The biological functions of seed OBs are dependent on structural proteins, principally oleosins, caleosins, and steroleosins, which are embedded in the OB phospholipid monolayer. Oleosin and caleosin proteins are specific to plants and mainly act as OB structural proteins and are important for the biogenesis, stability, and dynamics of the organelle; whereas steroleosin proteins are also present in mammals and play an important role in steroid hormone metabolism and signaling. Significant progress using new genetic, biochemical, and imaging technologies has uncovered the roles of these proteins. Here, we review recent work on the structural or metabolic roles of these proteins in OB biogenesis, stabilization and degradation, lipid homeostasis and mobilization, hormone signal transduction, stress defenses, and various aspects of plant growth and development.

Xanthoceras sorbifolium (yellowhorn) is a woody oil plant with super stress resistance and excellent oil characteristics. The yellowhorn oil can be used as biofuel and edible oil with high nutritional and medicinal value. However, genetic studies on yellowhorn are just in the beginning, and fundamental biological questions regarding its very long-chain fatty acid (VLCFA) biosynthesis pathway remain largely unknown. In this study, we reconstructed the VLCFA biosynthesis pathway and annotated 137 genes encoding relevant enzymes. We identified four oleosin genes that package triacylglycerols (TAGs) and are specifically expressed in fruits, likely playing key roles in yellowhorn oil production. Especially, by examining time-ordered gene co-expression network (TO-GCN) constructed from fruit and leaf developments, we identified key enzymatic genes and potential regulatory transcription factors involved in VLCFA synthesis. In fruits, we further inferred a hierarchical regulatory network with MYB-related ( XS03G0296800 ) and B3 ( XS02G0057600 ) transcription factors as top-tier regulators, providing clues into factors controlling carbon flux into fatty acids. Our results offer new insights into key genes and transcriptional regulators governing fatty acid production in yellowhorn, laying the foundation for efforts to optimize oil content and fatty acid composition. Moreover, the gene expression patterns and putative regulatory relationships identified here will inform metabolic engineering and molecular breeding approaches tailored to meet biofuel and bioproduct demands.

Lipid droplets (LDs) are intracellular organelles critical for energy storage and lipid metabolism. They are typically composed of an oil core coated by a monolayer of phospholipids and proteins such as oleosins. The mechanistic details of LD biogenesis remain poorly defined. However, emerging evidence suggest that their formation is a spatiotemporally regulated process, occurring at specific sites of the endoplasmic reticulum defined by a specific set of lipids and proteins. Here, we show that sterols are required for formation of oleosin-coated LDs in Arabidopsis. Analysis of sterol pathway mutants revealed that deficiency in several ∆ 5 -sterols accounts for the phenotype. Importantly, mutants deficient in these sterols also display reduced LD number, increased LD size and reduced oil content in seeds. Collectively, our data reveal a role of sterols in coordinating the synthesis of oil and oleosins and their assembly into LDs, highlighting the importance of membrane lipids in regulating LD biogenesis. Lipid droplet biogenesis originates at the endoplasmic reticulum and is defined by a specific set of lipids and proteins. Here, the authors show that sterols play an important role in coordinating oil and oleosin biosynthesis for the formation of lipid droplets in plant leaves and seeds.

Increasing seed oil content is one of the most important breeding goals for soybean due to a high global demand for edible vegetable oil. However, genetic improvement of seed oil content has been difficult in soybean because of the complexity of oil metabolism. Determining the major variants and molecular mechanisms conferring oil accumulation is critical for substantial oil enhancement in soybean and other oilseed crops. In this study, we evaluated the seed oil contents of 219 diverse soybean accessions across six different environments and dissected the underlying mechanism using a high-resolution genome-wide association study (GWAS). An environmentally stable quantitative trait locus (QTL), GqOil20, significantly associated with oil content was identified, accounting for 23.70% of the total phenotypic variance of seed oil across multiple environments. Haplotype and expression analyses indicate that an oleosin protein-encoding gene (GmOLEO1), colocated with a leading single nucleotide polymorphism (SNP) from the GWAS, was significantly correlated with seed oil content. GmOLEO1 is predominantly expressed during seed maturation, and GmOLEO1 is localized to accumulated oil bodies (OBs) in maturing seeds. Overexpression of GmOLEO1 significantly enriched smaller OBs and increased seed oil content by 10.6% compared with those of control seeds. A time-course transcriptomics analysis between transgenic and control soybeans indicated that GmOLEO1 positively enhanced oil accumulation by affecting triacylglycerol metabolism. Our results also showed that strong artificial selection had occurred in the promoter region of GmOLEO1, which resulted in its high expression in cultivated soybean relative to wild soybean, leading to increased seed oil accumulation. The GmOLEO1 locus may serve as a direct target for both genetic engineering and selection for soybean oil improvement.

Lipid droplets (LDs) are organelles that are necessary for eukaryotic and prokaryotic metabolism and energy storage. They have a unique structure consisting of a spherical phospholipid monolayer encasing neutral lipids such as triacylglycerol (TAG). LDs have garnered increased interest for their implications in disease and for drug delivery applications. Consequently, there is an increased need for tools to study their structure, composition, and dynamics in biological contexts. In this work, we utilize CHARMM‐GUI Membrane Builder to simulate and analyze LDs with and without a plant LD protein, oleosin. The results show that Membrane Builder can generate biologically relevant all‐atom LD systems with relatively short equilibration times using a new TAG library having optimized headgroup parameters. TAG molecules originally inserted into a lipid bilayer aggregate in the membrane center, forming a TAG‐only core flanked by two monolayers. The TAG‐only core thickness stably grows with increasing TAG mole fraction. A 70 % TAG system has a core that is thick enough to house oleosin without its interactions with the distal leaflet or disruption of its secondary structure. We hope that Membrane Builder can aid in the future study of LD systems, including their structure and dynamics with and without proteins. CHARMM‐GUI Membrane Builder can be used to build biologically relevant simulations of lipid droplet models with and without proteins using an extensive library of triacylglycerol lipids. Membrane Builder generates lipid droplet models with easily tunable sizes and compositions, while keeping equilibration times relatively short. These features make it a prime tool for the computational study of lipid droplets.

Soybean is an important oilseed crop and major dietary protein resource, yet the molecular processes and regulatory mechanisms involved in biosynthesis of seed storage substances are not fully understood. The B3 domain transcription factor (TF) LEC2 essentially regulates embryo development and seed maturation in other plants, but is not functionally characterized in soybean. Here, we characterize the function of a soybean LEC2 homolog, GmLEC2a, in regulating carbohydrate catabolism, triacylglycerol (TAG) biosynthesis, and seed development. The experimental analysis showed that GmLEC2a complemented Arabidopsis mutant defects in seedling development and TAG accumulation. Over-expression of in Arabidopsis seeds increased the TAG contents by 34% and the composition of long chain fatty acids by 4% relative to the control seeds. Transcriptome analysis showed that ectopic expression of in soybean hairy roots up-regulated several sets of downstream TF genes , Gm that regulate the seed development and production of seed storage substances. regulated the lipid transporter genes and oil body protein gene . The genes involved in carbohydrate biosynthesis and storage, such as sucrose synthesi , and catabolism of TAG, such as lipases in hairy roots were down-regulated. GmLEC2a targeted metabolic genes for seed protein in soybean.

Summary Duckweeds are amongst the fastest growing of higher plants, making them attractive high‐biomass targets for biofuel feedstock production. Their fronds have high rates of fatty acid synthesis to meet the demand for new membranes, but triacylglycerols (TAG) only accumulate to very low levels. Here we report on the engineering of Lemna japonica for the synthesis and accumulation of TAG in its fronds. This was achieved by expression of an estradiol‐inducible cyan fluorescent protein‐Arabidopsis WRINKLED1 fusion protein (CFP‐AtWRI1), strong constitutive expression of a mouse diacylglycerol:acyl‐CoA acyltransferase2 (MmDGAT), and a sesame oleosin variant (SiOLE(*)). Individual expression of each gene increased TAG accumulation by 1‐ to 7‐fold relative to controls, while expression of pairs of these genes increased TAG by 7‐ to 45‐fold. In uninduced transgenics containing all three genes, TAG accumulation increased by 45‐fold to 3.6% of dry weight (DW) without severely impacting growth, and by 108‐fold to 8.7% of DW after incubation on medium containing 100 μm estradiol for 4 days. TAG accumulation was accompanied by an increase in total fatty acids of up to three‐fold to approximately 15% of DW. Lipid droplets from fronds of all transgenic lines were visible by confocal microscopy of BODIPY‐stained fronds. At a conservative 12 tonnes (dry matter) per acre and 10% (DW) TAG, duckweed could produce 350 gallons of oil/acre/year, approximately seven‐fold the yield of soybean, and similar to that of oil palm. These findings provide the foundation for optimizing TAG accumulation in duckweed and present a new opportunity for producing biofuels and lipidic bioproducts. Triacylglycerol accumulation in duckweed (Lemna japonica) increased by 108‐fold to 8.7% of dry weight upon the expression of an inducible CFP‐Arabidopsis WRI1, along with constitutive expression of mouse DGAT2 and a variant sesame OLEOSIN.

Lipid droplets (LDs) serve as the primary storage site for neutral lipids in plant cells, with growing evidence supporting many additional biological roles, such as in lipid homeostasis, signalling, trafficking, inflammatory responses and inter‐organelle communication. While the biogenesis and structure of LDs in seeds and other plant tissues have been well‐documented, the full range of their functions has yet to be elucidated. Plant LDs encapsulate a hydrophobic neutral lipid core, enveloped by a phospholipid monolayer embedded with specific proteins. Despite their tissue‐specific diversity, a range of methods for LD isolation from plant materials has been established, facilitating lipidomic and proteomic characterisation. This knowledge has facilitated studies into the potential applications of LDs, particularly in pharmaceutical biotechnology. This review explores the multifunctional nature and biogenesis of plant LDs, highlights recent advances in LD fractioning from plant materials, explores factors affecting their stability, and discusses the potential of mimicking natural LDs using artificial lipid nano‐droplets (ALNDs) and similar synthetic lipid‐based formulations. It also underscores the significance of LD‐based delivery systems in pharmaceutical applications, emphasising their emerging potential in enhancing drug solubility, bioavailability and targeted delivery. Finally, future research directions are highlighted, focusing on scaling up LD isolation, optimising ALND and other formulations, and investigating their pharmacokinetics and long‐term stability for more widespread clinical applications.

Metabolic engineering to divert carbon flux from sucrose to oil in high biomass crop like sugarcane is an emerging strategy to boost lipid yields per hectare for biodiesel production. Sugarcane stems comprise more than 70% of the crops' biomass and can accumulate sucrose in excess of 20% of their extracted juice. The energy content of oils in the form of triacylglycerol (TAG) is more than twofold that of carbohydrates. Here, we report a step change in TAG accumulation in sugarcane stem tissues achieving an average of 4.3% of their dry weight (DW) in replicated greenhouse experiments by multigene engineering. The metabolic engineering included constitutive co‐expression of wrinkled1; diacylglycerol acyltransferase1‐2; cysteine‐oleosin; and ribonucleic acid interference‐suppression of sugar‐dependent1. The TAG content in leaf tissue was also elevated by more than 400‐fold compared to non‐engineered sugarcane to an average of 8.0% of the DW and the amount of total fatty acids reached about 13% of the DW. With increasing TAG accumulation an increase of 18:1 unsaturated fatty acids was observed at the expense of 16:0 and 18:0 saturated fatty acids. Total biomass accumulation, soluble lignin, Brix and juice content were significantly reduced in the TAG hyperaccumulating sugarcane lines. Overcoming this yield drag by engineering lipid accumulation into late stem development will be critical to exceed lipid yields of current oilseed crops. Metabolic engineering to divert carbon flux from sucrose to oil in high biomass crop like sugarcane is an emerging strategy to boost lipid yields per hectare for biodiesel production. Here we report a step change in triacylglycerol (TAG) accumulation in sugarcane stem tissues achieving an average of 4.3% of their dry weight (DW) by multigene engineering. The metabolic engineering included constitutive co‐expression of wrinkled1; diacylglycerol acyltransferase1‐2; cysteine‐oleosin; and ribonucleic acid interference‐suppression of sugar‐dependent1. The TAG content in leaf tissue was also elevated by more than 400‐fold compared to non‐engineered sugarcane to an average of 8.0% of the DW.