Production of 22:2^Δ5,Δ13 and 20:1^Δ5 in Brassica carinata and soybean breeding lines via introduction of Limnanthes genes

Seed oils of meadowfoam (Limnanthes douglasii, L. alba) contain very long-chain fatty acids of strategic importance for a number of industrial applications. These include the monoene 20 1^Δ5 and the diene 22:2^Δ5,Δ13. Engineering of meadowfoam-type oils in other oilseed crops is desirable for the production of these fatty acids as industrial feedstocks. Accordingly, we have targeted Brassica carinata and soybean (Glycine max) to trangenically engineer the biosynthesis of these unusual fatty acids. An L. douglasii seed-specific cDNA (designated Lim Des5) encoding a homolog of acyl-coenzyme A desaturases found in animals, fungi and cyanobacteria was expressed in B. carinata, which resulted in the accumulation of up to 10% 22:2^Δ5,Δ13 in the seed oil. In soybean, co-expression of Lim Des5 with a cDNA (Lim FAE1) encoding an FAEl (elongase complex condensing enzyme) homolog from L. douglasii resulted in the accumulation of 20:1 ^Δ5 to approximately 10% of the total fatty acids of seeds. The content of C₂₀ and C₂₂ fatty acids was also increased from <0.5% in non-transformed soybean seeds to >25% in seeds co-expressing the Lim. douglasii Des5 and FAE1 cDNAs. In contrast, expression of the Lim Des5 in Arabidopsis did not produce the expected 20:2^Δ5,Δ11 in the seed oil. Cumulatively, these results demonstrate the utility of soybean and B. carinata for the production of vegetable oils containing novel C ₂₀ and C₂₂ fatty acids, and confirm that the preferred substrates of the Lim Des5 are 20:0 and 22:1^Δ3, respectively.