Biosynthesis of plant cuticular wax components

所有的陆地植物都有一层蜡状的“皮肤”，叫做角质层，它是防止水分流失、紫外线、病原体和昆虫的保护屏障。角质层主要由角质和蜡质形式的脂质组成。角质层内的蜡质嵌在三维角质层基质中，而角质层外的蜡质通常以结晶形式覆盖在外表面。我们研究项目的总体目标是了解角质层蜡是如何合成并沉积在植物表面的。遗传研究表明，大量蛋白质参与角质层蜡的产生，但只有少数已被确定。我们正在利用模式植物拟南芥（Arabidopsis thaliana）中的蜡缺乏或“cer”突变体来鉴定和功能表征蜡生物合成和沉积相关的基因产物。我们最近发现了CER4，它编码一种形成酒精的脂肪酰基辅酶a还原酶。这是已知最早的蜡生物合成酶之一。我们建议研究CER4和CER4样蛋白的底物特异性，并利用这些信息来操纵角质层蜡的组成。我们还计划确定CER4的亚细胞位置，以深入了解蜡生物合成的区隔化。此外，还将研究另外两种蛋白质CER1和WAX2/CER3的代谢作用。我们将使用基于图谱的方法克隆更多的CER基因，目的是鉴定新的蜡生物合成酶、调节蛋白和参与蜡分泌的蛋白。这些基因产物的分子和生化研究将继续进行，以确定它们各自在蜡生物合成中的作用。我们的工作将对了解植物蜡的生物合成途径和植物角质层的发育做出重要贡献。最终，我们的目标是为积累蜡的基因工程提供重要信息，以提高作物植物抵御干旱、病原体和其他环境胁迫的能力。

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.