Laboratory of Plant Stress Ecophysiology and Biotechnology, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, China.
National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
Plant Cell Physiol. 2018 Apr 1;59(4):806-822. doi: 10.1093/pcp/pcy020.
The cuticle coats the primary aerial surfaces of land plants. It consists of cutin and waxes, which provide protection against desiccation, pathogens and herbivores. Acyl cuticular waxes are synthesized via elongase complexes that extend fatty acyl precursors up to 38 carbons for downstream modification pathways. The leaves of 21 barley eceriferum (cer) mutants appear to have less or no epicuticular wax crystals, making these mutants excellent tools for identifying elongase and modification pathway biosynthetic genes. Positional cloning of the gene mutated in cer-zh identified an elongase component, β-ketoacyl-CoA synthase (CER-ZH/HvKCS1) that is one of 34 homologous KCSs encoded by the barley genome. The biochemical function of CER-ZH was deduced from wax and cutin analyses and by heterologous expression in yeast. Combined, these experiments revealed that CER-ZH/HvKCS1 has a substrate specificity for C16-C20, especially unsaturated, acyl chains, thus playing a major role in total acyl chain elongation for wax biosynthesis. The contribution of CER-ZH to water barrier properties of the cuticle and its influence on the germination of barley powdery mildew fungus were also assessed.
表皮层覆盖在陆地植物的主要气生表面。它由角质和蜡质组成，为植物提供了防止干燥、病原体和食草动物侵害的保护。酰基辅质蜡是通过延长酶复合物合成的，该复合物将脂肪酸前体延长至 38 个碳，用于下游修饰途径。21 个大麦eceriferum（cer）突变体的叶片似乎没有或几乎没有表皮蜡晶体，这使得这些突变体成为鉴定延长酶和修饰途径生物合成基因的优秀工具。cer-zh 突变基因的定位克隆鉴定出一个延长酶成分，β-酮酰基辅酶 A 合酶（CER-ZH/HvKCS1），它是大麦基因组中编码的 34 个同源 KCS 之一。CER-ZH 的生化功能是从蜡和角质分析以及在酵母中的异源表达中推断出来的。这些实验表明，CER-ZH/HvKCS1 对 C16-C20，特别是不饱和酰基链具有底物特异性，因此在蜡生物合成的总酰基链延长中起主要作用。还评估了 CER-ZH 对表皮层水屏障特性的贡献及其对大麦白粉菌萌发的影响。
