Yeats Trevor H, Huang Wenlin, Chatterjee Subhasish, Viart Hélène M-F, Clausen Mads H, Stark Ruth E, Rose Jocelyn K C
Department of Plant Biology, Cornell University, Ithaca, NY, 14853, USA.
Plant J. 2014 Mar;77(5):667-75. doi: 10.1111/tpj.12422. Epub 2014 Feb 11.
The aerial epidermis of all land plants is covered with a hydrophobic cuticle that provides essential protection from desiccation, and so its evolution is believed to have been prerequisite for terrestrial colonization. A major structural component of apparently all plant cuticles is cutin, a polyester of hydroxy fatty acids; however, despite its ubiquity, the details of cutin polymeric structure and the mechanisms of its formation and remodeling are not well understood. We recently reported that cutin polymerization in tomato (Solanum lycopersicum) fruit occurs via transesterification of hydroxyacylglycerol precursors, catalyzed by the GDSL-motif lipase/hydrolase family protein (GDSL) Cutin Deficient 1 (CD1). Here, we present additional biochemical characterization of CD1 and putative orthologs from Arabidopsis thaliana and the moss Physcomitrella patens, which represent a distinct clade of cutin synthases within the large GDSL superfamily. We demonstrate that members of this ancient and conserved family of cutin synthase-like (CUS) proteins act as polyester synthases with negligible hydrolytic activity. Moreover, solution-state NMR analysis indicates that CD1 catalyzes the formation of primarily linear cutin oligomeric products in vitro. These results reveal a conserved mechanism of cutin polyester synthesis in land plants, and suggest that elaborations of the linear polymer, such as branching or cross-linking, may require additional, as yet unknown, factors.
所有陆地植物的气生表皮都覆盖着一层疏水性角质层，该角质层提供了防止脱水的重要保护作用，因此其进化被认为是陆地定殖的先决条件。显然，所有植物角质层的一个主要结构成分是角质，它是一种羟基脂肪酸的聚酯；然而，尽管角质普遍存在，但其聚合物结构的细节以及形成和重塑机制仍未得到很好的理解。我们最近报道，番茄（Solanum lycopersicum）果实中的角质聚合是通过羟基酰基甘油前体的酯交换反应发生的，由GDSL基序脂肪酶/水解酶家族蛋白（GDSL）角质缺陷1（CD1）催化。在这里，我们展示了来自拟南芥和苔藓小立碗藓的CD1及其假定直系同源物的额外生化特性，它们代表了大GDSL超家族中一个独特的角质合成酶进化枝。我们证明，这个古老且保守的类角质合成酶（CUS）蛋白家族的成员作为聚酯合成酶，水解活性可忽略不计。此外，溶液态核磁共振分析表明，CD1在体外催化主要线性角质寡聚产物的形成。这些结果揭示了陆地植物中角质聚酯合成的保守机制，并表明线性聚合物的细化，如分支或交联，可能需要额外的、尚未知的因素。
