FIGURE 7.

Schematic representation of the epigenetic mechanism regulating development and diapause in H. armigera. Larvae were cultured at 20 °C and 14 h light:10 h dark (long day length) or 10 h light:14 h dark (short day length). Pupae develop without interruption and emerge as adults within 3 weeks under long-day conditions, whereas pupae enter diapause for over 3 months when reared under short-day conditions. In developing (nondiapausing) pupae, long-day length activates PTTH gene expression by stimulating photoperiod-sensitive (PPS) proteins and/or signals, which in turn activate PRC2-mediation of the methyl modification of histone H3 at lysine 27 (the green dot represents the trimethyl site) and initiate adult development. Short-day length represses PTTH gene expression with low activity of PRC2 and low level of the methyl modification, causing pupal diapause and lifespan extension.