Ovarian Dual Oxidase (Duox) Activity Is Essential for Insect Eggshell Hardening and Waterproofing

Background: Hardening of the insect eggshell is due to peroxidases that promote protein cross-linking via H2O2, from an unknown source. Results: In Rhodnius prolixus, this H2O2 is produced by Duox, and it also contributes to waterproofing, preventing desiccation. Conclusion: H2O2 from Duox has a double role in protecting the Rhodnius eggshell. Significance: Duox activity is essential to insect reproduction. 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.