Orcokinins contribute to the regulation of vitellogenin transcription in the cockroach Blattella germanica

- B. germanica OK gene codes for two mRNAs, BgOKA and BgOKB.
- BgOKA and BgOKB encode mainly OKA and OKB peptides, respectively.
- BgOKA mRNA is localized in brain, while BgOKB mRNA is localized in brain and midgut.
- BgOKs RNAi reduces oocyte growth and Vg expression, independently of JH.
- Results suggest that BgOK expression contributes to the regulation of vitellogenesis.

Orcokinins (OKs) are neuropeptides that were first identified in crustacean through their myotropic activity. In insects, the OK gene gives rise to two mRNAs coding for two different families of conserved mature neuropeptides: OKA and OKB. Although OKs are conserved in many insect species, its physiological role in this animal class is not fully understood. Until now prothoracicotropic, regulatory of light entrainment to the circadian clock and “awakening” activities have been reported for these peptides in different insect species. Here we report the identification of OKA and OKB precursors in the cockroach Blattella germanica. OKA mRNA was detected in brain, whereas OKB mRNA was detected both in brain and midgut. In vivo silencing of OK precursors suggests the involvement of OK gene products in the regulation of vitellogenin expression in the fat body, an action that appears to be independent of juvenile hormone. This is the first time that a function of this kind has been reported for OKs.