Cuticular wax biosynthesis, regulation and intracellular trafficking

角质蜡覆盖在陆地植物的地上表面，是防止水分流失、紫外线、病原体和昆虫的保护性屏障。蜡的主要成分来自饱和的超长链脂肪酸(VLCFAs；&GT；C20)，通过两条生物合成途径：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的角质蜡成分表明，蜡的生物合成在植物中高度保守。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，蜡生产是如何调节的，以及蜡是如何在到达植物表面的过程中在表皮细胞中运输的。我们一直在利用拟南芥蜡质缺失突变体来鉴定和鉴定与角质层蜡质沉积相关的基因。在这个应用中，我们建议使用这种方法来(1)研究超过28个碳的VLCFA是如何合成的，这些碳是形成大量植物蜡质所必需的；(2)确定我们最近发现的RNA降解核糖核酸酶如何控制蜡的积累；以及(3)确定蜡从其在ER膜上的合成部位分泌到质膜所需的细胞成分。我们相信，这项拟议的研究将极大地促进我们对角质层蜡质沉积的了解，并导致识别出一些基因，使我们能够操纵蜡质的组成和积累，以提高作物的抗旱性，以及它们对病原体和虫害的抗性。此外，蜡的生物合成知识具有工业应用，因为蜡具有独特的物理性质，使其成为广泛产品(如化妆品、食品添加剂、工业润滑剂)的有用底物。同样，对烷烃形成的酶学的了解将为大规模生产可再生的高效生物燃料以减少我们对化石燃料的依赖奠定基础。

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.