Cuticular wax biosynthesis, regulation and intracellular trafficking

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Cuticular wax covers aerial surfaces of land plants and serves as a protective barrier against water loss, UV-light, pathogens and insects. Major wax components are derived from saturated very long chain fatty acids (VLCFAs; >C20 in length) via two biosynthetic pathways: an alcohol-forming and an alkane-forming pathway. Similar cuticular wax compositions found in Arabidopsis and other species suggest that wax biosynthesis is highly conserved in plants. However, our knowledge in several key areas remains limited, including how wax precursors are formed, how wax production is regulated, and how waxes are transported in epidermal cells en route to the plant surface. We have been using Arabidopsis wax-deficient mutants to identify and functionally characterize genes involved in cuticular wax deposition. In this application, we propose to use this approach to (1) investigate how VLCFA longer than 28 carbons are synthesized, which are required for the formation of the bulk of plant waxes (2) determine how an RNA-degrading ribonuclease that we have recently discovered controls wax accumulation, and (3) identify cellular components required for wax secretion from its site of synthesis on the ER membranes to the plasma membrane. We believe that the proposed research will significantly advance our understanding of cuticular wax deposition and result in the identification of genes that will allow us to manipulate wax composition and accumulation to improve tolerance of crop plants to drought, and their resistance to pathogens and insects. Additionally, knowledge of wax biosynthesis has industrial applications because waxes possess unique physical properties that make them useful substrates for a wide range of products (e.g. cosmetics, food additives, industrial lubricants). Likewise, understanding of the enzymology of alkane formation will lay the basis for large-scale production of renewable high-efficiency biofuels to reduce our dependence on fossil fuels.