Award details

Transcriptional control of polyunsaturated fatty acid synthesis in fish

Reference	BB/C51237X/1
Principal Investigator / Supervisor	Professor Douglas Tocher
Co-Investigators / Co-Supervisors	Dr Michael Leaver, Professor Alan Teale, Dr Xiaozhong Zheng
Institution	University of Stirling
Department	Institute of Aquaculture
Funding type	Research
Value (£)	280,241
Status	Completed
Type	Research Grant
Start date	01/04/2005
End date	30/06/2008
Duration	39 months

Abstract

Fish species vary in their ability to convert plant-derived C18 polyunsaturated fatty acids (PUFA) to essential longer chain highly unsaturated fatty acids(HUFA), including the n-3 HUFA eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA). This variation is associated with their complement of fatty acid desaturase and elongase enzymes. Although salmonid fish are capable of producing DHA from linolenic acid (18:3n-3), and so express all the activities required in this pathway, the activity is insufficient to maintain n-3HUFA levels in fish fed vegetable oils rich in C18 PUFA, but devoid of HUFA. In marine fish such as cod, the activity of the pathway is very low due to deficiencies at one or more of the steps. Our primary hypothesis is that understanding the molecular basis of HUFA biosynthesis and its regulation in fish will allow us to optimise the activity of the pathway to enable efficient and effective use of vegetable oils in aquaculture feeds whilst maintaining the nutritional quality of farmed fish for the consumer. This project aims to elucidate the molecular basis of long-chain fatty acid biosynthesis and its regulation in fish through isolation and characterisation of the genes involved, and determination of how their expression is controlled and regulated. Genomic libraries from Atlantic salmon and cod will be screened and putative fatty acid desaturase and elongase genes identified. The cDNAs for these will be cloned by established methods, and functionally characterised by expression in the yeast Saccharomyces cerevisiae. Genomic organisation will be determined by Southern analysis and putative upstream promoter regions determined by gene walking. Using the sequence data potential transcription factor binding sites will then be mapped in silico. These upstream sequences will be investigated by deletion and site-directed mutagenesis to identify functional promoters and regulatory (cis-) elements, including those for SREBPs and PPARs. DNA binding of transcription factors will be confirmed by EMSA and their ligands investigated using reporter gene constructs and transactivation assays. The mechanisms involved in the nutritional and hormonal control of the expression of desaturase and elongase genes will be tested in in vitro studies using salmonid and marine fish cell lines. The ultimate aim is to develop practical, non-GM strategies for the nutritional activation and up-regulation of fatty acyl desaturase and elongase genes to optimise the HUFA biosynthetic ability of farmed Atlantic salmon and cod.

Summary

unavailable

Committee	Closed Committee - Agri-food (AF)
Research Topics	Animal Health, Diet and Health, Microbiology
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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