Astrid Meyer

Metabolic engineering of fatty acids for breeding of new oilseed crops: strategies, problems and first results

Abbreviations: ACP = acyl carrier protein. – ACS = acyl-CoA synthase. – ARA = arachidonic acid. – CLA = conjugated linoleic acid. – CPT = CDP-choline :1,2-diacylglycerol cholinephosphotransferase. – DAGAT = acyl-CoA :1,2-diacylglycerol acyltransferase. – DHA = docosahexaenoic acid. – EPA = eicosapentaenoic acid. – ER = endoplasmic reticulum. – FAE = fatty acid elongase. – FAR = acyl-CoA reductase. – GLA = γ-linolenic acid. – GPAT = acyl-CoA : glycerol-3-phosphate acyltransferase. – HEAR = high-erucic acid rapeseed. – KAS = β-ketoacyl-ACP synthase. – KCS = β-ketoacyl-CoA synthase. – LPAAT = acyl-CoA : lysophosphatidic acid acyltransferase. – LPCAT = acyl-CoA : lysophosphatidylcholine acyltransferase. – MCF = medium-chain fatty acids. – mRNAi = antisense messenger ribonucleic acid containing inverted-repeat sequences. – PC = phosphatidylcholine. – PDAT = phospholipid : 1,2-diacylglycerol acyltransferase. – PLA2 = phospholipase A2. – TAG = triacylglycerol. – VLCPUFA = very long-chain polyunsaturated fatty acids. – WS = wax synthase

Fatty Acid Desaturases from the Diatom Phaeodactylum Tricornutum

Very long-chain polyunsaturated fatty acids (PUFAs) such as arachidonic acid (ARA, 20:4Δ5,8,11,14) or eicosapentaenoic acid (EPA, 20:5Δ5,8,11,14,17) have been shown to display many beneficial effects on human health. Today, the main commercial sources for these fatty acids are fish oil and micro-organisms. Since biotechnology may allow the production of specific fatty acids by genetic engineering of crops, the possibility of producing PUFAs in rapeseed or linseed has lead to the search for the genes encoding the enzyme activities involved in PUFA biosynthesis.

Biochemical Studies on the Production of Docosahexaenoic Acid (DHA) in Euglena and Thraustochytrium

A strategy based on fatty acid α-oxidation was developed to discriminate Δ4-desaturation and the involvement of a polyketide synthase system in the production of docosahexaenoic acid (22:6Δ4,7,10,13,16,19) from exogenously supplied docosapentaenoic acid (22:5Δ4,7,10,13,16,19) in Euglena gracilis and Thraustochytrium sp. Thraustochytrium also seems to possess an ω3-desaturase activity working on C22 fatty acid substrates. This activity was apparently missing in Euglena.