To diapause or to reproduce? Circadian genes and juvenile hormone decide.

Prior to winter, shortening days inform insects to stop breeding and enter reproductive quiescence, diapause. This occurs through signals from the brain, inhibiting secretion of juvenile hormone (JH) that is required for oogenesis. Reproduction naturally restarts as the day-length extends, or it can be induced in previously diapausing females by supplying JH. We have shown how JH switches the insect gut from diapause to reproductive program. Under long photoperiod, JH acts through its receptor Met and proteins of the circadian clock, Cycle and Clock, upon a regulatory feedback loop, which in turn activates genes typical of reproduction. Under short days, when JH is absent, this loop switches to diapause genes. Besides the finding that the JH receptor cooperates with the components of the circadian clock, the surprising discovery is that this novel regulation does not involve daily rhythms but depends on the photoperiod – a seasonal rhythm.

• Bajgar A., Jindra M., Doležel D. (2013) Autonomous regulation of the insect gut by circadian genes acting downstream of juvenile hormone signaling. Proceedings of the National Academy of Sciences of the United States of America 110: 4416-21.

  DOI: 10.1073/pnas.1217060110