title: In vivo packaging of triacylglycerols enhances Arabidopsis leaf biomass and energy density.
abstract: Our dependency on reduced carbon for energy has led to a rapid increase in the search for sustainable alternatives and a call to focus on energy densification and increasing biomass yields. In this study, we generated a uniquely stabilized plant structural protein (cysteine [Cys]-oleosin) that encapsulates triacylglycerol (TAG). When coexpressed with diacylglycerol O-acyltransferase (DGAT1) in Arabidopsis (Arabidopsis thaliana), we observed a 24% increase in the carbon dioxide (CO2) assimilation rate per unit of leaf area and a 50% increase in leaf biomass as well as approximately 2-, 3-, and 5-fold increases in the fatty acid content of the mature leaves, senescing leaves, and roots, respectively. We propose that the coexpression led to the formation of enduring lipid droplets that prevented the futile cycle of TAG biosynthesis/lipolysis and instead created a sustained demand for de novo lipid biosynthesis, which in turn elevated CO2 recycling in the chloroplast. Fatty acid profile analysis indicated that the formation of TAG involved acyl cycling in Arabidopsis leaves and roots. We also demonstrate that the combination of Cys-oleosin and DGAT1 resulted in the highest accumulation of fatty acids in the model single-cell eukaryote, Saccharomyces cerevisiae. Our results support the notion that the prevention of lipolysis is vital to enabling TAG accumulation in vegetative tissues and confirm the earlier speculation that elevating fatty acid biosynthesis in the leaf would lead to an increase in CO2 assimilation. The Cys-oleosins have applications in biofuels, animal feed, and human nutrition as well as in providing a tool for investigating fatty acid biosynthesis and catabolism.
authors.affiliation: AgResearch, Ltd., Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
authors.forename: Somrutai
authors.initials: S
authors.lastname: Winichayakul
authors.forename: Richard William
authors.initials: RW
authors.lastname: Scott
authors.forename: Marissa
authors.initials: M
authors.lastname: Roldan
authors.forename: Jean-Hugues Bertrand
authors.initials: JH
authors.lastname: Hatier
authors.forename: Sam
authors.initials: S
authors.lastname: Livingston
authors.forename: Ruth
authors.initials: R
authors.lastname: Cookson
authors.forename: Amy Christina
authors.initials: AC
authors.lastname: Curran
authors.forename: Nicholas John
authors.initials: NJ
authors.lastname: Roberts
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D051048:Diacylglycerol O-Acyltransferase / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D008055:Lipids / Q000032:analysis; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified; D015202:Protein Engineering / Q000379:methods; D012441:Saccharomyces cerevisiae / Q000235:genetics; D057057:Serine Proteases / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D005227:Fatty Acids; D008055:Lipids; D014280:Triglycerides; C079353:oleosin protein, Arabidopsis; D002245:Carbon Dioxide; C579477:DGAT1 protein, Arabidopsis; D051048:Diacylglycerol O-Acyltransferase; D057057:Serine Proteases; D003545:Cysteine