Cloning And Functional Characterization Of The 3-Ketoacyl-CoA Synthase (KCS) Genes From Malania Oleifera

Nervonic acid 24:1 A15(cis-15-tetracosenoic acid)is a very long-chain monounsaturated fatty acid and exists in nature as an elongation product of oleic acid.There is an increasing interest in production of high nervonic acid oils for pharmaceutical,nutraceutical and industrial applications.Nervonic acid content is as high as 40%in the seed oil of rare plant Malania oleifera.Using rapid-amplification of cDNA ends and polymerase chain reaction approach,we have isolated genes from Malania oleifera L.,which encodes a 3-ketoacyl-CoA synthase(KCS),the first component of the elongation complex involved in synthesis of nervonic acid.The Malania KCSs under the control of the seed-specific promoter,phaseolin,were transformed into Arabidopsis.The T3 generations of transgenic Arabidopsis lines expressing the Malania KCS showed that seed-specific expression resulted in relatively large comparative increases in nervonic acid proportions in Arabidopsis seed oil.Seed-specific expression in Arabidopsis thaliana resulted in up to a 4-fold increase in the proportion of erucic acid.The nervonic acid level reached up to 5.3%and erucic acid was increased up to 8.1%in transgenic Arabidopsis lines.These results indicate that the MoKCS11 gene encodes a condensing enzyme involved in the biosynthesis of very long-chain fatty acids utilizing monounsaturated acyl substrates,with a strong capability for improving the erucic acid and nervonic acid content.