From the Instituto de Bioquímica Médica Leopoldo De Meis, Programa de Biologia Molecular e Biotecnología, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590.
J Biol Chem. 2013 Dec 6;288(49):35058-67. doi: 10.1074/jbc.M113.522201. Epub 2013 Oct 30.
In insects, eggshell hardening involves cross-linking of chorion proteins via their tyrosine residues. This process is catalyzed by peroxidases at the expense of H2O2 and confers physical and biological protection to the developing embryo. Here, working with Rhodnius prolixus, the insect vector of Chagas disease, we show that an ovary dual oxidase (Duox), a NADPH oxidase, is the source of the H2O2 that supports dityrosine-mediated protein cross-linking and eggshell hardening. RNAi silencing of Duox activity decreased H2O2 generation followed by a failure in embryo development caused by a reduced resistance to water loss, which, in turn, caused embryos to dry out following oviposition. Phenotypes of Duox-silenced eggs were reversed by incubation in a water-saturated atmosphere, simultaneous silencing of the Duox and catalase genes, or H2O2 injection into the female hemocoel. Taken together, our results show that Duox-generated H2O2 fuels egg chorion hardening and that this process plays an essential role during eggshell waterproofing.
在昆虫中，卵壳的硬化涉及通过酪氨酸残基交联卵壳蛋白。这个过程由过氧化物酶催化，消耗 H2O2，并为发育中的胚胎提供物理和生物保护。在这里，我们与恰加斯病的昆虫载体——丽蝇属进行合作，表明卵巢双氧化酶（Duox），一种 NADPH 氧化酶，是支持二酪氨酸介导的蛋白质交联和卵壳硬化的 H2O2 的来源。Duox 活性的 RNAi 沉默降低了 H2O2 的产生，随后由于对水分丧失的抵抗力降低，胚胎发育失败，这反过来又导致胚胎在产卵后变干。通过在饱和水蒸汽环境中孵育、同时沉默 Duox 和过氧化氢酶基因、或向雌性血腔注射 H2O2，可逆转 Duox 沉默卵的表型。总之，我们的结果表明，Duox 产生的 H2O2 为卵壳的硬化提供动力，并且该过程在卵壳防水过程中发挥着重要作用。
