Defra - Department for Environment, Food and Rural Affairs.

Science Search

Science and Research Projects

Return to Science Search homepage   Return to Project List

Functional genomics in marine algae to discover genes that can be used to produce docosahexaenoic acid in oilseed crops - NF0507

Description
Summary
Docosahexaenoic acid (DHA, 22:64,7,10,13,16,19) is a long chain polyunsaturated fatty acid (LPUFA) with important nutraceutical and pharmaceutical applications. The principal dietary source of DHA is fish. However fish accumulate pollutants, the extracted oil has unpleasant odour and the proportion of specific desirable fatty acids from this source is difficult to control. Fish are also a declining resource that can not supply the expanding market. Attempts to enhance the LPUFA content of meat products by manipulating animal feed have met with limited success. Some companies have cultivated marine microorganisms such as Crypthecodinium cohnii which biosynthesise specific desirable PUFAs. Although there have been successes using this approach, cultivation of algae is technically demanding and costly. Higher plants do not typically biosynthesise LPUFA’s such as DHA. The low cost production of DHA in the vegetable oil of a crop such as oilseed rape is an extremely attractive target for genetic engineering and as such qualifies as a relevant industrial product group in the MAFF policy for crop science research. Current attempts to engineer LPUFA production in transgenic plants rely on a targeted approach on specific genes using existing biochemical information. This approach has failed to identify all of the genes necessary for high level production of DHA in a crop species. Developments in genomics technologies over the last 3 years means that an entirely new large scale functional genomics approach can now be used to rapidly identify key genes involved in a particular biochemical pathway or any other biological process. The resources available in the MAFF funded Plant Genome Facility will allow us to adopt a large scale genomics approach in the current work. The project will involve the production of an expressed sequence tag (EST) database, bioinformatics, metabolite profiling and microarray analysis, to discover genes responsible for the production of DHA in a marine algae. The global nature of the approach should result in the discovery of key genes that can be used to engineer the synthesis of oil containing DHA in crop plants.
Objective
1) Use metabolite profiling of fatty acids to identify suitable growth conditions that result in induction of DHA biosynthesis in Crypthecodinium cohnii (6 months)
2) Produce a cDNA library of mRNA isolated from a C. cohnii under growth conditions that induce DHA biosynthesis (12 months)
3) Generate 2-3,000 EST (expressed sequence tag) sequences from the cDNA library having first established redundancy status of library and performed selected subtractive hybridisation if necessary (16 months)
4) Generate a database of EST sequence information and use advanced bioinformatics procedures to identify genes that are associated with fatty acid metabolism (e.g. desaturases, elongases, acyltransferases, acyl-CoA synthetases) (16 months)
5) Use these genes to produce ‘boutique’ and general microarray chips that can be used for detailed gene expression studies. (boutique chips, 18 months; general chips, 24 months)
6) Use microarrays to identify key genes that are induced under those environmental conditions that also result in the induction of DHA biosynthesis – as monitored by metabolite profiling by standard GC procedures (24 and 30 months)
7) Perform functional assays on candidate genes by heterologous overexpression in convenient host such as Saccharomyces cereviseae or Eschericia coli (36 months)
8) Overexpression of candidate genes in Arabidopsis and evaluation of transgenics for altered LPUFA content (48 months)
Project Documents
• Executive Summary : Functional genomics in marine algae to discover genes that can be used to produce docosahexaenoic acid (DHA) in oilseed crops   (63k)
Time-Scale and Cost
From: 2000

To: 2004

Cost: £380,153
Contractor / Funded Organisations
University - York
Keywords
Agri-Industrial              
Arable Farming              
Biotechnology              
Crops              
Farming              
GM Non-Food              
Fields of Study
Non-Food Crops