Höfer Rene, Briesen Isabel, Beck Martina, Pinot Franck, Schreiber Lukas, Franke Rochus
Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, D-53115 Bonn, Germany.
J Exp Bot. 2008;59(9):2347-60. doi: 10.1093/jxb/ern101.
The lipophilic biopolyester suberin forms important boundaries to protect the plant from its surrounding environment or to separate different tissues within the plant. In roots, suberin can be found in the cell walls of the endodermis and the hypodermis or periderm. Apoplastic barriers composed of suberin accomplish the challenge to restrict water and nutrient loss and prevent the invasion of pathogens. Despite the physiological importance of suberin and the knowledge of the suberin composition of many plants, very little is known about its biosynthesis and the genes involved. Here, a detailed analysis of the Arabidopsis aliphatic suberin in roots at different developmental stages is presented. This study demonstrates some variability in suberin amount and composition along the root axis and indicates the importance of omega-hydroxylation for suberin biosynthesis. Using reverse genetics, the cytochrome P450 fatty acid omega-hydroxylase CYP86A1 (At5g58860) has been identified as a key enzyme for aliphatic root suberin biosynthesis in Arabidopsis. The corresponding horst mutants show a substantial reduction in omega-hydroxyacids with a chain length <C(20), demonstrating that CYP86A1 functions as a hydroxylase of root suberized tissue. Detailed expression studies revealed a strong root specificity and a localized expression in the root endodermis. Transgenic expression of CYP86A1 fused to GFP distributed CYP86A1 to the endoplasmic reticulum, indicating that suberin monomer biosynthesis takes place in this sub-cellular compartment before intermediates are exported in the apoplast.
亲脂性生物聚酯木栓质形成重要的边界，以保护植物免受周围环境的影响，或分隔植物体内的不同组织。在根中，木栓质可在内皮层、下皮层或周皮的细胞壁中发现。由木栓质组成的质外体屏障应对了限制水分和养分流失以及防止病原体入侵的挑战。尽管木栓质具有重要的生理意义，且许多植物的木栓质组成已为人所知，但对其生物合成及相关基因却知之甚少。本文对拟南芥根在不同发育阶段的脂肪族木栓质进行了详细分析。该研究表明，沿根轴木栓质的含量和组成存在一定变异性，并指出ω-羟基化在木栓质生物合成中的重要性。通过反向遗传学，细胞色素P450脂肪酸ω-羟化酶CYP86A1（At5g58860）已被鉴定为拟南芥根脂肪族木栓质生物合成的关键酶。相应的突变体显示链长<C(20)的ω-羟基酸大幅减少，表明CYP86A1作为根木栓化组织的羟化酶发挥作用。详细的表达研究揭示了其强烈的根特异性以及在根内皮层中的局部表达。与绿色荧光蛋白融合的CYP86A1的转基因表达将CYP86A1分布到内质网，表明木栓质单体生物合成在该亚细胞区室中发生，然后中间体被输出到质外体。
