Cloning of fatty acid biosynthetic genes β-ketoacyl CoA synthase, fatty acid elongase, stearoyl-ACP desaturase, and fatty acid desaturase and analysis of expression in the early developmental stages of flax (Linum usitatissimum L.) seeds

Flaxseed products in the form of nutraceuticals and health foods are now widespread. This success is mainly attributable to their essential fatty acids. To identify the key genes involved in fatty acids biosynthesis, a cDNA library made from flax bolls collected at 12 days after anthesis (12 DAA) was constructed and screened for ss-ketoacyl CoA synthase (KAS), fatty acid elongase (FAE), stearoyl-ACP desaturase (SAD), and fatty acid desaturase (FAD). Condensing enzymes (KAS and FAE) were shown to be represented in higher numbers in the library as compared to the desaturases (SAD and FAD). Multiple sequence alignment showed that the FAD sequence (linFAD) reported herein was an endoplasmic reticulum microsomal fatty acid desaturase, whereas linKAS appeared to be related to the very long fatty acid condensing protein suggesting that other members of these two gene families may be present in flax. Furthermore, linKAS and linFAD were shown to be expressed as early as the day of anthesis and fatty acid profiling at anthesis and at 2 DAA revealed high content of palmitate (16:0), linoleate (18:2), and linolenate (118:3) as compared to stearate (18:0) and oleate (18:1). This result suggests a high activity of condensing enzymes and delta 12 and delta 15 desaturases at these early developmental stages. This report is the first dealing with flax genomics linking fatty acid profiling and lipid biosynthetic pathway. (C) 2004 Elsevier Ireland Ltd. All rights reserved.