Producing Wax Esters in Transgenic Plants by Expression of Genes Derived from Jojoba

Jojoba [Simmondsia chinensis, Simmondsiaceae, (Link) Schnieder], a native of deserts of the American Southwest, is unusual and perhaps unique amongst higher plants in that its seed storage lipids are liquid waxes rather than triglycerides. These waxes are esters of long chain (mostly; C20, C22, and C24), monounsaturated, fatty acids and alcohols. The waxes are produced in developing embryos during seed formation. Jojoba oil is primarily used as an ingredient in cosmetics. The stability of the oil under high temperatures and pressures suggests it has potential as a component of industrial lubricants, however, the high price of jojoba oil has served as a barrier to its widespread use for these types of applications. The production of liquid waxes in an oilseed crop more suited to large scale agriculture could allow the production of wax esters at a price more acceptable to industrial users. As in other plants, jojoba fatty acids up to 18 carbons in length are synthesized in plastids. Oleic acid (18:1) is exported from plastids, and its CoA esters serve as substrates for microsomal membrane enzymes involved in wax formation. Three enzyme activities are involved in the formation of waxes (Fig.1, Pollard et al. 1979): 1. Fatty acid elongase (FAE) is a complex of four enzymes that converts 18:1 to eicosenoic acid (20:1), erucic acid (22:1), and nervonic acid (24:1). 2. An acyl-CoA reductase catalyzes the formation of fatty alcohols from 20:1-, 22:1-, and 24:1-CoAs. 3. Wax synthase is an acyltransferase that forms wax esters from fatty alcohol and acyl-CoA substrates. In this manuscript we describe the isolation of genes encoding the enzymes involved in wax synthesis and the use of these genes to produce wax esters in transgenic arabidopsis plants.