Figure 5

A hypothetical explanation of clock gene RNAi in Riptortus pedestris . The same molecular machinery is required for the circadian rhythm of cuticle deposition and the photoperiodic response [129,130,147-149]. In the intact group, the circadian clock generates rhythmic transcription of ccg, regulating the circadian rhythm with alternating deposition of polarized cuticle layers and nonpolarized cuticle layers, which are observed as bright (indicated by small arrows) and dark layers, respectively, under a light microscope with crossed polarizers. The intact group shows a clear photoperiodic response: Female adults develop their ovaries under long-day conditions but enter diapause under short-day conditions. In the per or cry-m RNAi group, constant high levels of ccg transcripts abolish the circadian rhythm of cuticle deposition, and only nonpolarized layers are deposited. Photoperiodism is also disrupted and ovarian development is induced irrespective of the photoperiod. In the cyc or Clk RNAi group, constant low levels of ccg transcripts abolish the circadian rhythm and only polarized layers are deposited. In this case as well, photoperiodism is disrupted and diapause is induced irrespective of the photoperiod.