Biosynthesis of plant cuticular wax components

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All land plants are coated with a waxy "skin" called the cuticle that serves as a protective barrier against water loss, UV light, pathogens, and insects.  The cuticle is comprised primarily of lipids in the form of cutin and waxes.  Intracuticular waxes are embedded in the three-dimensional cutin matrix whereas epicuticular waxes, often in crystalline form, cover the outer surface.        The overall goal of our research program is to understand how cuticular waxes are synthesized and then deposited on the surfaces of plants.  Genetic studies indicate that a large number of proteins participate in cuticular wax production, but only a handful of these have been identified.  We are taking advantage of wax-deficient or 'cer' mutants in the model plant Arabidopsis thaliana to identify and functionally characterize gene products involved in wax biosynthesis and deposition.  We have recently identified CER4, which encodes an alcohol-forming fatty acyl-CoA reductase.  This is one of the first known wax biosynthetic enzymes.  We propose to examine the substrate specificities of CER4 and CER4-like proteins and use this information to manipulate cuticular wax composition.  We also plan to determine the sub-cellular location of CER4 to gain insights into the compartmentalization of wax biosynthesis.  In addition, the putative metabolic roles of two other proteins, CER1 and WAX2/CER3, will be investigated.  We will clone additional CER genes using map-based approaches with the aim of identifying novel wax biosynthetic enzymes, regulatory proteins, and proteins involved in wax secretion.  Molecular and biochemical studies of these gene products will be pursued to determine their respective roles in wax biosynthesis.        Our work will make significant contributions towards understanding plant wax biosynthetic pathways and the development of the plant cuticle.  Ultimately, our aim is to generate important information for the genetic engineering of wax accumulation to improve the ability of crop plants to withstand drought, pathogens, and other environmental stresses.