ORIGINAL PAPER Transgenic production of arachidonic acid in oilseeds James R. Petrie • Pushkar Shrestha • Srinivas Belide • Maged P. Mansour • Qing Liu • James Horne • Peter D. Nichols • Surinder P. Singh Received: 18 November 2010 / Accepted: 21 April 2011 Ó Springer Science+Business Media B.V. 2011 Abstract We describe a transgenic microalgal D9-elongase pathway transformed in both Brassica napus and Arabidopsis thaliana seed resulting in the production of arachidonic acid (ARA). This pathway is noteworthy for both the production of ARA in seed tissue and the low levels of intermediate C20 fatty acids that accumulate. We also demonstrate that the arachidonic acid is naturally enriched at the sn2 position in triacylglycerol. This is the first report of ARA production by the D9-elongase pathway in an oilseed. Keywords Arachidonic acid Á LC-PUFA Á Delta-9 elongase Á Delta-8 desaturase Á Brassica napus Introduction Long-chain (CC 20 ) polyunsaturated fatty acids (LC- PUFA) such as the omega-6 (x-6) arachidonic acid (ARA, 20:4 D5,8,11,14 ) and the x-3 eicosapentaenoic acid (EPA, 20:5 D5,8,11,14,17 ) and docosahexaenoic acid (DHA, 22:6 D4,7,10,13,16,19 ) are essential to human health and development. In particular, studies have indicated positive effects on infant cognitive devel- opment after ARA supplementation and an Interna- tional Expert Group have advised the inclusion of PUFA such as ARA and DHA in infant formulas (Koletzko et al. 2005). Additionally, ARA deficiency is characterized by hair loss, fatty liver degeneration, anaemia and reduced fertility in adults although such deficiencies are not common in adults given the relatively high consumption of ARA, especially in Western diets. At a cellular level, ARA is a compo- nent of cell membranes and is also a precursor to eicosanoids, a family of molecules which have broad roles in regulating inflammatory responses, blood clotting and cell signalling (Kinsella et al. 1990). ARA is an essential fatty acid for many mammals and is synthesised by a number of micro-organisms including many microalgae, thraustochytrids, fungi and some bacteria (e.g. Volkman et al. 1989; Nichols et al. 1997; Lewis et al. 1999). The most common synthesis pathway appears to commence with a D6-desaturation of linoleic acid (LA, 18:2 D9,12 ) to produce c-linolenic acid (GLA, 18:3 D6,9,12 ) which is subsequently acted on by a D6-elongase to produce J. R. Petrie Á P. Shrestha Á S. Belide Á Q. Liu Á S. P. Singh (&) Food Futures National Research Flagship, CSIRO Plant Industry, PO Box 1600, Canberra, ACT 2601, Australia e-mail: surinder.singh@csiro.au S. Belide Department of Biotechnology, Sreenidhi Institute of Science and Technology, Yamnampet, Ghatkesar, 501301 Hyderabad, AP, India M. P. Mansour Á P. D. Nichols Food Futures National Research Flagship, CSIRO Marine and Atmospheric Research, GPO Box 1538, Hobart, TAS 7000, Australia J. Horne Central Science Laboratory, University of Tasmania, Hobart, TAS 7001, Australia 123 Transgenic Res DOI 10.1007/s11248-011-9517-7