AgResearch, Ltd., Grasslands Research Centre, Private Bag 11008, Palmerston North 4442, New Zealand.
Plant Physiol. 2013 Jun;162(2):626-39. doi: 10.1104/pp.113.216820. Epub 2013 Apr 24.
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.
我们对低碳能源的依赖导致人们对可持续替代品的研究迅速增加，并呼吁将重点放在能源密集化和提高生物质产量上。在这项研究中，我们生成了一种独特的稳定植物结构蛋白（半胱氨酸[Cys]-油蛋白），它可以包裹三酰基甘油（TAG）。当与二酰基甘油 O-酰基转移酶（DGAT1）在拟南芥（Arabidopsis thaliana）中共表达时，我们观察到单位叶面积的二氧化碳（CO2）同化率提高了 24%，叶片生物量增加了 50%，成熟叶片、衰老叶片和根的脂肪酸含量分别增加了约 2、3 和 5 倍。我们提出，共表达导致持久的脂滴形成，阻止了 TAG 生物合成/脂解的徒劳循环，而是为从头合成脂质创造了持续的需求，从而提高了叶绿体中的 CO2 循环。脂肪酸谱分析表明，TAG 的形成涉及拟南芥叶片和根中的酰基循环。我们还证明，Cys-油蛋白和 DGAT1 的组合导致模式单细胞真核生物酿酒酵母中脂肪酸的积累最高。我们的结果支持这样一种观点，即防止脂解对于在营养组织中积累 TAG 至关重要，并证实了早先的推测，即在叶片中提高脂肪酸生物合成会导致 CO2 同化的增加。Cys-油蛋白在生物燃料、动物饲料和人类营养方面具有应用价值，并且为研究脂肪酸生物合成和分解代谢提供了一种工具。
