Cuticular wax biosynthesis, regulation and intracellular trafficking

表皮蜡覆盖陆地植物的气生表面，并作为防止水分流失、紫外线、病原体和昆虫的保护屏障。主要的蜡组分通过两种生物合成途径衍生自饱和极长链脂肪酸（VLCFA;长度>C20）：醇形成途径和烷烃形成途径。在拟南芥和其他物种中发现的类似表皮蜡组成表明蜡的生物合成在植物中是高度保守的。然而，我们在几个关键领域的知识仍然有限，包括蜡前体是如何形成的，蜡的产生是如何调节的，以及蜡是如何在表皮细胞中运输到植物表面的。我们一直在使用拟南芥蜡缺陷突变体，以确定和功能特性的基因参与角质层蜡沉积。在本申请中，我们建议使用这种方法来（1）研究如何合成长于28个碳的VLCFA，这是形成大量植物蜡所必需的（2）确定我们最近发现的RNA降解核糖核酸酶如何控制蜡积累，和（3）鉴定蜡分泌所需的细胞组分，所述蜡分泌从ER膜上的合成位点到质膜。我们相信，拟议的研究将显着推进我们对表皮蜡沉积的理解，并导致识别基因，使我们能够操纵蜡的组成和积累，以提高作物对干旱的耐受性，以及对病原体和昆虫的抗性。此外，蜡生物合成的知识具有工业应用，因为蜡具有独特的物理性质，使其成为广泛产品（例如化妆品，食品添加剂，工业润滑剂）的有用基质。同样，了解烷烃形成的酶学将为大规模生产可再生高效生物燃料奠定基础，以减少我们对化石燃料的依赖。

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.