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Roles of the circadian clock and endocrine regulator in the photoperiodic response of the brown‐winged green bug Plautia stali

Takaaki Tamai, Sakiko Shiga, Shin G. Goto
Physiological entomology 2019 v.44 no.1 pp. 43-52
Plautia stali, RNA interference, adults, biosynthesis, circadian clocks, corpora allata, females, insects, juvenile hormones, locomotion, messenger RNA, ovarian development, photoperiod, photoperiodism, regulator genes
The physiological mechanisms underlying photoperiodism in insects have been studied extensively, although the associated molecular machinery remains largely unknown. In the present study, we investigate the roles of the circadian clock gene cycle (cyc) and the endocrine regulator gene myoinhibitory peptide (Mip) in the photoperiodic response of the brown‐winged green bug Plautia stali Scott (Hemiptera, Pentatomidae). Typically, adult females of this species develop their ovaries under long‐day conditions, whereas they suppress its development under short‐day conditions. We find that RNA interference (RNAi) directed against cyc causes malfunction of the circadian clock governing the locomotor activity rhythm and yields abnormal activity profiles not only under constant darkness, but also under light/dark conditions. RNAi directed against cyc and Mip disrupts the photoperiodic response in ovarian development. cyc RNAi suppresses the ovarian development even under long‐day conditions, whereas Mip RNAi induces it even under short‐day conditions. We propose that the core circadian clock gene cyc regulates the photoperiodic response and that Mip is the causal regulator of juvenile hormone biosynthesis in the corpus allatum. Neither photoperiod, nor cyc RNAi affect Mip mRNA levels, and therefore it remains unknown how the photoperiodic information is processed and mediated by Mip.