Abstract
Worldwide demand for vegetable oil is projected to double within the next 30 years due to increasing food, fuel, and industrial requirements. There is therefore great interest in metabolic engineering strategies that boost oil accumulation in plant tissues, however, efforts to date have only achieved levels of storage lipid accumulation in plant tissues far below the benchmark to meet demand. Monoacylglycerol acyltransferase (MGAT) is predominantly associated with lipid absorption and resynthesis in the animal intestine where it catalyzes monoacylglycerol (MAG) to form diacylglycerol (DAG), and then triacylglycerol (TAG). In contrast plant lipid biosynthesis routes do not include MGAT. Rather, DAG and TAG are either synthesized from glycerol-3-phosphate by a series of three subsequent acylation reactions, or originated from phospholipids via an acyl editing pathway. Mouse MGATs 1 and 2 have been shown to increase oil content transiently in Nicotiana benthamiana leaf tissue by 2.6 fold. Here we explore the feasibility of this approach to increase TAG in Arabidopsis thaliana seed. The stable MGAT2 expression resulted in a significant increase in seed oil content by 1.32 fold. We also report evidence of the MGAT2 activity based on in vitro assays. Up to 3.9 fold increase of radiolabeled DAG were produced in seed lysate which suggest that the transgenic MGAT activity can result in DAG re-synthesis by salvaging the MAG product of lipid breakdown. The expression of MGAT2 therefore creates an independent and complementary TAG biosynthesis route to the endogenous Kennedy pathway and other glycerolipid synthesis routes.
Highlights
Demand for production and use of plant oils is rapidly increasing and current agricultural practices are unable to produce sufficient amounts cost-effectively
Arabidopsis thaliana seeds were dried in a dessicator for 24 h and approximately 4 mg of seed were transferred to 2 mL glass vials with Teflon-lined screw caps
DAG produced by MGAT2 may subsequently be converted to TAG by native mechanisms including diacylglycerol acyltransferase (DGAT) activity, which may be upregulated in response to the DAG accumulation (Petrie et al, 2012), further investigation is required to confirm this
Summary
Demand for production and use of plant oils is rapidly increasing and current agricultural practices are unable to produce sufficient amounts cost-effectively. Multiple approaches are being employed to develop plants with altered oil content to meet this demand. One approach that biotechnologists are exploring is the potential of transgenic technologies to boost the metabolic flux of carbon into oil in the developing seed (Weselake et al, 2008; Bates et al, 2013). Oil Increase in MGAT Seed lipid synthesis pathways play an important role in energy storage. Rather complex interchanges occur between different neutral lipid pools of the Kennedy pathway and polar membrane lipids. Weselake et al (2008) reported that neutral lipid production is affected by the interaction of a growing suite of enzymes with intermediates of Kennedy pathway Rather complex interchanges occur between different neutral lipid pools of the Kennedy pathway and polar membrane lipids. Weselake et al (2008) reported that neutral lipid production is affected by the interaction of a growing suite of enzymes with intermediates of Kennedy pathway
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