Understanding the role of lipases in controlling seed storage oil composition

Vegetable oils (triacylglycerols) are an important source of human nutrition and also serve as a versatile feedstock for the chemical industry; in many cases providing a sustainable substitute for petrochemicals. The properties of these oils determine their use and are dependent on the types of fatty acids that are attached at each of the three positions on the glycerol backbone. It has long been a goal of scientist to create crops producing 'designer' oils that are tailored for specific applications. Substantial progress has been made in understanding how different fatty acids are made but a lack of knowledge concerning how they can be incorporated efficiently into oil is currently proving a barrier to the commercial realization of many designer oilseed crops. Investigation of how fatty acids are assembled into oil has revealed that the process is complex in plants and, in addition to the substrate specificity of the enzymes that attach each fatty acid, various editing mechanism exist that also help determine which fatty acids are incorporated and which are not. Lipases are one family of enzymes that have been proposed to play a role in this editing/remodeling but none have been characterized. We have therefore used a genetic screen to identify at least two lipase mutants that are altered in the fatty acid composition of their seed oil. The objective of this research is to understand how these lipases control fatty acid composition of oil, to discover whether others can be found, and also to determine if they contribute to the barriers that limit the accumulation of two high-value 'unusual' fatty acids in a designer oilseed crop.

Triacylglycerols (TAGs) derived from plants are an important commodity, with relevance for human nutrition and also for the chemical industry where they provide feedstock for a range of products such as paints, lubricants, cosmetics, detergents, plastics and resins, and also biofuels. The utility of TAGs lies in the species of fatty acid esterified to each of the three positions on the glycerol backbone. It has long been a goal of scientist to create crops producing 'designer' oils that are tailored for specific applications. Substantial progress has been made in understanding how different fatty acids are made but a lack of knowledge concerning how they can be incorporated efficiently into oil is currently proving a barrier to the commercial realization of many designer oilseed crops. The TAG biosynthetic pathway is complex in plants and, in addition to the substrate specificity of the enzymes that attach each fatty acid, various editing mechanism exist that also help determine which fatty acids are incorporated and which are not. Lipases (or more generally acyl hydrolases) are one family of enzymes that have been proposed to play a role in this editing/remodeling but none have been characterized at the molecular level. We have therefore used a reverse genetic screen to identify at least two lipase/acyl hydrolase mutants in Arabidopsis thaliana that are altered in the fatty acid composition of their seed oil. The objective of this research is to understand how these enzymes control the fatty acid composition of oil, discover whether others can be found, and also to determine if they contribute to the barriers that limit the accumulation of hydroxylated FAs and very long chain omega-3 polyunsaturated FAs in the seed oil of Camelina sativa plants engineered to produce these high-value 'unusual' FAs.

The research carried out in this project will deliver basic knowledge that may well be necessary to better tailor the fatty acid composition of oil from oilseed crops, either by conventional breeding or by genetic modification. As such, the work ultimately has the potential to benefit industry and generate wealth for the UK. Both the food and non-food applications of plant oils contribute to BBSRC priorities of Food security, Bioenergy and industrial biotechnology and Basic bioscience underpinning health. The PI, Co-I and the host institution (RRes) have contacts with several crop breeding and Agri-biotech companies and are well-placed to exploit any intellectual property that is generated from the project by seeking out industrial collaborators. The project provides an excellent training environment for a postdoctoral researcher looking to gain technical expertise in molecular biology, protein expression and analytical chemistry, a research track record in metabolic pathway engineering and contacts with academic groups and industry in the field.