Institut de Biologie Moléculaire des Plantes, UPR2357-CNRS, Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France.
Plant Cell Physiol. 2014 Feb;55(2):455-66. doi: 10.1093/pcp/pct182. Epub 2013 Dec 5.
The plant cuticle is a chemically heterogeneous lipophilic layer composed of a cutin polymer matrix and waxes which covers the aerial parts of plants. This layer plays an essential role in the survival of plants by protecting them from desiccation and (a)biotic stresses. Knowledge on the gene networks and mechanisms regulating the synthesis of cuticle components during organ expansion or stress response remains limited however. Here, using five loss-of-function mutants for histone monoubiquitination, we report on the role of two RING E3 ligases, namely HISTONE MONOUBIQUITINATION 1 and 2 (HUB1 and HUB2), in the selective transcriptional activation of four cuticle biosynthesis genes in Arabidopsis thaliana. Microscopy observations showed that in hub1-6 and hub2-2 mutants irregular epidermal cells and disorganized cuticle layers were present in rosette leaves. Water loss measurements on excised rosettes demonstrated that cuticular permeability was significantly increased in the mutants. Chemical analysis of cuticle components revealed that the wax composition was changed and that cutin 16:0 dicarboxylic acid was significantly reduced in all hub mutants. Analysis of transcript levels of selected genes indicated that LACS2, ATT1 and HOTHEAD involved in cutin biosynthesis and CER1 involved in wax biosynthesis were down-regulated in the hub mutants, while the expression of LACERATA, CER3, CER6 and CER10 remained unchanged. Chromatin immunoprecipitation assays further showed that hub mutants are impaired in dynamic changes of histone H2B monoubiquitination at several loci of down-regulated genes. Taken together, these data establish that the regulation of cuticle composition involves chromatin remodeling by H2B monoubiquitination.
植物表皮是由角质聚合物基质和蜡组成的化学异质亲脂层，覆盖在植物的气生部分。这一层通过防止植物干燥和（非生物）胁迫，对植物的生存起着至关重要的作用。然而，关于调节器官扩张或应激反应过程中角质层成分合成的基因网络和机制的知识仍然有限。在这里，我们使用五个组蛋白单泛素化功能丧失突变体，报告了两个 RING E3 连接酶，即 HISTONE MONOUBIQUITINATION 1 和 2（HUB1 和 HUB2），在拟南芥中选择性转录激活四个角质层生物合成基因中的作用。显微镜观察表明，在 hub1-6 和 hub2-2 突变体中，罗勒叶存在不规则的表皮细胞和组织化的角质层。对离体罗勒叶的水分损失测量表明，突变体的角质层通透性显著增加。角质层成分的化学分析表明，蜡成分发生了变化，所有 hub 突变体中的角质 16:0 二酸都显著减少。对选定基因的转录水平分析表明，参与角质生物合成的 LACS2、ATT1 和 HOTHEAD 以及参与蜡生物合成的 CER1 在 hub 突变体中下调，而 LACERATA、CER3、CER6 和 CER10 的表达保持不变。染色质免疫沉淀测定进一步表明，hub 突变体在几个下调基因的组蛋白 H2B 单泛素化的动态变化中受到损害。综上所述，这些数据表明，角质层组成的调节涉及到通过 H2B 单泛素化进行染色质重塑。
