Figures (1)  Tables (1)

    • Figure 1. 

      Schematic representation of TAG biosynthesis and lipid droplet formation. (a) TAG biosynthesis and lens formation: TAG assembly occurs in the ER via the Kennedy pathway (G3P → LPA → PA → DAG → TAG), supplemented by acyl-CoA flux from acyl editing at PC and acyl-transfer from PC via PDAT or PDCT. Newly synthesized TAG aggregate into lens-like structures via phase separation on the leaflets of the ER bilayer. (b) SEIPIN-driven lipid droplet budding: SEIPIN interacts with specific proteins and lipids to drive lipid droplet budding via phase separation and membrane remodeling. (c) LD growth and fusion mechanisms: cytosolic LDs grow via Ostwald ripening and fuse through protein-mediated mechanisms. G3P, sn-3 glycerol 3-phosphate; LPA, lysophosphatidic acid; PA, phosphatidic acid; PC, phosphatidylcholine; LPC, lysophosphatidylcholine; DAG, 1,2-diacyl-sn-glycerol; FFA, free fatty acids; TAG, triacylglycerol; DGAT, diacylglycerol acyltransferase; GPAT, sn-glycerol-3-phosphate acyltransferase; LACS, long-chain acyl-CoA synthetase; LPAAT, lysophosphatidic acid acyltransferase; LPCAT, lysophosphatidylcholine acyltransferase; PDAT, phospholipid:diacylglycerol acyltransferase; PDCT, phosphatidylcholine:diacylglycerol cholinephosphotransferase; PLA2, phospholipase A2; PAH, phosphatidate phosphatase; FIT2, fat storage-inducing transmembrane protein 2 from mammals; LDAF1, lipid droplet assembly factor 1 from mammals; NEM1, Nuclear Envelope Morphology 1 from mammals; PEX30, Peroxin 30 from Saccharomyces cerevisiae; ABHD1, α/β hydrolase domain-containing protein 1 from Chlamydomonas; VPS13A/C, Vacuolar Protein Sorting-associated Protein 13 A/C from mammals; SNARE, Soluble N-ethylmaleimide-sensitive factor attachment protein receptors from mammals; CIDE, Cell Death-Inducing DFFA-like Effector from mammals. Overexpression of asterisk-marked proteins enhances seed oil content.

    • StageProteinFunctionPlant oil content enhancementRef.
      TAG assembly and lens FormationGPATG3P to LPA using acyl-CoA-derived acyl/
      LPAATLPA to PA using acyl-CoA-derived acylYes[20]
      PAHPA to DAG/
      DGAT1DAG to TAG using acyl-CoA-derived acylYes[22]
      PDAT1DAG to TAG using PC-derived acylNo[5]
      LACSFFA to FA-CoAYes[21]
      PLA2PC to LPC and FFA/
      LPCATLPC to PC using acyl-CoA-derived acyl/
      PDCTTransfer of the headgroup from PC to DAG/
      LD buddingFIT2Converts luminal phospholipids to DAG, driving LD
      budding toward the cytoplasm      		Yes[25]
      SEIPINDrive lipid phase separation, triggering LD nucleationYes[24]
      LDAFMember of SEIPIN Complex/
      LDAPMember of SEIPIN ComplexNo[34]
      NEM1Member of SEIPIN Complex/
      PEX30Member of SEIPIN Complex/
      LDIPMember of SEIPIN Complex/
      LD growth and fusionVPS13A/CFacilitate neutral lipid transport from the ER to LDs/
      SNAREsFacilitate LD membrane fusion machinery, enabling
      inter-organelle bridges      		/
      CIDEsMediate TAG transfer between LDsYes[18,26]

      Table 1. 

      Protein candidates to enhance plant oil content,