Understanding the role of lipases in controlling seed storage oil composition
Lead Research Organisation:
Rothamsted Research
Department Name: Plant Biology & Crop Science
Abstract
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.
Technical Summary
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.
Planned Impact
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.
Organisations
Publications
Van Erp H
(2014)
Seed Storage Reserve Analysis.
in Bio-protocol
Menard GN
(2017)
Genome Wide Analysis of Fatty Acid Desaturation and Its Response to Temperature.
in Plant physiology
Menard GN
(2018)
Natural variation in acyl editing is a determinant of seed storage oil composition.
in Scientific reports
Luginbuehl LH
(2017)
Fatty acids in arbuscular mycorrhizal fungi are synthesized by the host plant.
in Science (New York, N.Y.)
Kelly AA
(2013)
The sugar-dependent1 lipase limits triacylglycerol accumulation in vegetative tissues of Arabidopsis.
in Plant physiology
Karp A
(2015)
Growing innovations for the bioeconomy.
in Nature plants
Haslam RP
(2013)
The modification of plant oil composition via metabolic engineering--better nutrition by design.
in Plant biotechnology journal
Eastmond PJ
(2015)
Arabidopsis uses two gluconeogenic gateways for organic acids to fuel seedling establishment.
in Nature communications
Eastmond P
(2014)
Biomass oil crops: more than a pipe dream?
in Biofuels
Chen GQ
(2016)
Expression of Castor LPAT2 Enhances Ricinoleic Acid Content at the sn-2 Position of Triacylglycerols in Lesquerella Seed.
in International journal of molecular sciences
Description | 1) We have identified and characterised a lipase in Arabidopsis who's function specifically effects the level of monounsaturated fatty acids (oleic acid) in seed oil. 2) We have characterise the effect of temperature on the oleic acid content of Arabidopsis seed oil, identified genetic variation in this trait and fine-mapped a major QTL that controls it. 3) We have shown that the capacity of the acyl editing (or Land's) cycle, which provides oleic acid for fatty acid desaturation, varies greatly among ecotypes of Arabidopsis because the many don't express a key enzyme (LPCAT2) in their seeds. |
Exploitation Route | 1) The market of vegetable oils that are very rich in oleic acid is growing owing to their food and non-food applications. Breeders could screen for mutants in the lipase we identified and use this to increase the oleic acid content of oilseed crops such winter oilseed rape, without harming membrane function in their vegetative tissues at low temperature. 2) The effect of ambient temperature on seed oil composition is problematic for oil processors because it leads to unwanted variation in product quality. Therefore breeders could use allelic variation at the locus we have mapped to help minimise this effect in major crops such as soybean, oilseed rape and sunflower. 3) Acyl editing has a strong influence of the efficiency of incorporation of modified fatty acids (e.g. those with arrangements of double bonds and various functional groups) into storage oil in seeds. Many of these modified fatty acids have specific food and non-food applications. Hence, knowing that the capacity of this cycle can vary greatly within a species is potentially useful to breeders and biotechnologists trying to improve oil quality in crops. |
Sectors | Agriculture Food and Drink Manufacturing including Industrial Biotechology |
Description | The fatty acid composition of seed oils determines their uses. Several breeding companies have developed oilseed varieties with high monounsaturated and low polyunsaturated fatty acid content for cooking applications. The genes we identified and characterised can potentially be used to enhance the level and stability of this trait, and we communicated our findings to several companies. |
First Year Of Impact | 2016 |
Sector | Agriculture, Food and Drink |
Description | ISIS travel award |
Amount | £4,484 (GBP) |
Funding ID | BB/N021932/1 |
Organisation | Biotechnology and Biological Sciences Research Council (BBSRC) |
Sector | Public |
Country | United Kingdom |
Start | 04/2016 |
End | 06/2016 |
Description | Seeding Catalyst Awards |
Amount | £10,000 (GBP) |
Funding ID | BB/SCA/Rothamsted/17 |
Organisation | Biotechnology and Biological Sciences Research Council (BBSRC) |
Sector | Public |
Country | United Kingdom |
Start | 11/2017 |
End | 02/2018 |