Thomas McKeon
United States Department of Agriculture, USA
Title: A review of obstacles to production of ricinoleate in transgenic plant oils
Biography
Biography: Thomas McKeon
Abstract
The castor oil plant produces a seed containing >50% oil with up to 90% ricinoleic acid, 12-hydroxy oleic acid. The presence of the mid-chain hydroxyl group imparts physical and chemical properties making castor oil uniquely useful as a feedstock for numerous products. However, limited production of castor has allowed petroleum derived products to displace many castor oil based products from the marketplace, despite better performance characteristics of the castor based products. The toxic protein ricin has impeded widespread cultivation of castor. As a result, there is great interest in developing transgenic plants that produce such hydroxy fatty acids (HFA). For over 50 years, biochemists and plant scientists have been challenged to elucidate the means, by which castor makes such unique oil. Identification of the oleoyl hydroxylase activity led to cloning expressing the hydroxylase gene in a transgenic plant resulting in <20% HFA. A number of enzymes involved in castor oil biosynthesis have been identified and some of these have been cloned and tested in model plants. The highest level of HFA achieved is 33%. This presentation will describe research results from our lab and review results of other researchers. The summary of research results to date allows us to identify both evolutionary considerations and competition from endogenous pathways as key factors limiting HFA oil content. Research aimed at enhancing HFA in transgenic oils will answer questions of fundamental value in understanding how seeds control oil and fatty acid content. However, focus on improving castor will ultimately support expanded castor oil production.