Laccase2 is required for sclerotization and pigmentation of Aedes albopictus eggshell

Abstract

Laccase (EC 1.10.3.2) is a member of multicopper oxidases that have been found in higher plants, fungus, bacterium, and insects. Two types of laccase genes have been detected in many species of insects: laccase1 and laccase2. It has been identified that laccase2 enzyme may play a key role in sclerotization and pigmentation of insect cuticle. But few attentions were given to the biological role of laccase2 in the synthesizing of similar structures, such as oothecae, eggshell, or silk cocoons. We cloned laccase2 gene from Aedes albopictus, one main mosquito vector of dengue virus in China. An upregulation of laccase2 gene was observed after a blood meal in female adult mosquitoes, suggesting that laccase2 gene may have an involvement in the development of ovary. RNA interference experiment was performed by using adult female mosquitoes. Female mosquitoes were injected with 20 ng of double-strain RNA into the thorax. Pigmentation of mosquito eggshell was blocked that these eggs never became dark. And the incomplete sclerotization of eggshell weakened the stability and flexibility of the eggs. These eggs without enough protection were deformed and died in water. These results demonstrate that laccase2 plays a critical role in the development of eggs of A. albopictus. Laccase2 may provide a novel target for mosquito control and management.

Physical features and chitin content of eggs from the mosquito vectors Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus: Connection with distinct levels of resistance to desiccation

“…Up to date this approach is yet not feasible for mosquito embryos. There do exist a few RNAi studies with mosquitoes aiming the egg but these are directed toward maternal genes that affect early embryogenesis (e.g., Wu et al, 2013) or siRNA directed silencing aiming late zygotic genes (e.g., Clemons et al, 2011). In both approaches, egg viability is compromised and therefore these methods can not be employed to address genes with the potential to affect mosquito egg viability under dehydrating conditions.…”

RNA interference: a promising biopesticide strategy against the African Sweetpotato Weevil Cylas brunneus

“…The functionality of RNAi in C. brunneus was confirmed by an experiment where the laccase2 gene expression was knocked down. This gene, encoding a copper-containing enzyme which oxidizes phenolic compounds to their corresponding quinones, was chosen based on its involvement in cuticle tanning and sclerotization and on the expectation that silencing this gene would result in a clear phenotypical effect, as reported earlier in C. puncticollis 20, T. castaneum 22, D. virgifera 23, Nephotettix cincticeps 24, Monochamus alternates 25 and Aedes albopictus 26. Treated C. brunneus weevils clearly showed defects in their cuticle development during and after pupation.…”

Suppression of Laccase 2 severely impairs cuticle tanning and pathogen resistance during the pupal metamorphosis of Anopheles sinensis (Diptera: Culicidae)

“…In the red flour beetle, stinkbug, and honey bee, the pupal cuticle or newly-molted adult becomes white and more flexible due to the depletion of Laccase 2 [38, 40, 42]. Additionally, the dysfunction of Laccase 2 in mosquito eggs results in pale and fragile eggshells, which further causes the eventual collapse of the eggs [39]. This evidence suggests that Laccase 2 is an important regulator in melanin synthesis and deposition.…”