Recipient Organization
NEW MEXICO STATE UNIVERSITY
1620 STANDLEY DR ACADEMIC RESH A RM 110
LAS CRUCES,NM 88003-1239
Performing Department
Entomology, Plant Pathology & Weed Science
Non Technical Summary
A need exists for the development of clean and renewable resources of high molecular weight industrial and commercial oil products. While there are many well developed oilseed crops none are efficient sources of these high value oils. Many undomesticated crops, particularly those adapted to harsh environments such as the desert, produce high levels of high value oils and waxes. The jojoba (Simmondsia chinensis) shrub is one example. Jojoba "beans" can contain up to 70% by weight of a high molecular weight liquid wax that has been utilized as a replacement for sperm whale oil. There has been a long standing interest in developing renewable sources of high molecular weight oil products including the wax esters produced by jojoba, carnauba palm (Copernicia cerifera), and other species to meet this need. The high molecular weight oils and waxes produced by these plants have a variety of uses including as industrial lubricants, food additives, cosmetics, and as renewable stocks for synthesis of compounds such as various adhesives, emmoliants, PEG's, natural plastics, nylons, and more. In spite of considerable efforts in the past decades to develop efficient production schemes for native oil-bearing desert plants such as jojoba efficient production methods capable of meeting demand have not been devised. Conventional oilseed crops could potentially provide a natural and renewable resource for high value oils and waxes. Characterization of the wax biosynthetic pathway in jojoba led to the discovery of a wax synthase capable catalyzing high molecular weight wax formation. Homology searches of other plant genes identified 11 candidate wax synthase genes in A. thaliana that are similar to the jojoba wax synthase. We hypothesize that high value wax ester production in conventional Brassica oilseed crops like rape seed can be increased by altering regulation of genes already within these Brassica spp.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The specific objectives described below comprise a straightforward plan for moving toward this long term goal: 1) Continued biochemical characterization of A. thaliana wax synthase genes to confirm wax synthase activity and characterize specific metabolic products produced by these genes; 2) Continued characterization of regulatory regions governing expression of wax synthase homologues in A. thaliana; 3) Continued high value oil and wax synthesis gene discovery work.
Project Methods
plant genetic and biochemical analysis that are established in the PD's lab. Procedures are outlined for each objective below. The cloning of the jojoba wax synthase gene was a significant step toward the goal of producing jojoba wax in oilseed crops (Lardizabal et al, 2000). While expression of these gene in A. thaliana did cause the accumulation of jojoba wax in the transgenic seeds the levels that accumulated were below that required for economically viability. Attempts to manipulate the precursor pools required for wax synthesis by expressing the jojoba wax synthase in high euricic acid brassica lines or co-expressing it with a jojoba fatty acid reductase failed to substantially increase jojoba wax accumulation levels (Metz et al, 2000). The limitations encountered on increasing high molecular weight wax accumulation are not well understood but may involve poor compatibility between the jojoba and Brassica enzymes. This is not surprising considering that jojoba is a member of the Euphorbeacea and not closely related to Brassica spp. Given that Brassica spp make very low levels of wax it was surprising to find that A. thaliana genome had numerous apparent homologues in its genome sequence (Klypin and Hanson, 2008; Lardzibal et al, 2000). This observation suggests that A. thaliana has the basic biochemical machinery necessary for wax synthesis and that detailed characterization of this machinery could allow either 1) modification of the biochemical pathways so that the jojoba wax synthase enzymes can be better fit into the Brassica wax synthesis pathways, or 2) that the existing Brassica enzymes could be manipulated to increase the amounts of wax produced using the native Brassica machinery. Manipulation of Brassica enzymes to achieve the goal of increasing wax production has several benefits including: 1) increased efficiency by avoiding disparate pathways containing enzymes from distantly related plants, and 2) simpler adoption in agricultural production since crops modified to over express their own enzymes are "cis-genic" rather than "trans-genic" and thus have lower public adoption and regulatory hurdles to clear for use in production. Therefore, the major goal of this proposal is to further initial work we have performed on characterization of the A. thaliana homologues of the jojoba wax synthase gene. The long term outcomes include developing a detailed understanding of the specific genes and regulatory elements involved in the production of specific waxes in Brassica spp. and a detailed understanding of the regulatory sequences controlling these genes. This information will enable the engineering of conventional oil seed crops to produce high value oil and wax products that can replace foreign petroleum sources of these compounds. In addition, these high value oil and wax products could also provide value added products that can increase the economic feasibility of bio-diesel production. Additional ongoing work also includes continuing analysis of desert plants to identify unique high value oils and waxes that could be incorporated into conventional oilseed crops in the future.