Molecular analysis of circadian photosensitivity and diapause in the jewel wasp Nasonia vitripennis

Cycling environmental conditions that vary with latitude have led to the evolution of intricate timing mechanisms. Nasonia vitripennis, a small parasitic wasp (Hymenoptera), is known to have strong light-driven seasonal response in the form of diapause (insect type of hibernation) signalled by short days of upcoming winter, as well as circadian rhythms in behaviours such as locomotor activity. Circadian rhythms are governed by a biological “clock”, whose molecular composition differs between species. Whether this clock also regulates seasonal rhythms is debated, as the regulation of the “seasonal timer” is poorly known. Because Nasonia is missing the clock protein CRYPTOCHROME1, a “light-sensor” for the clock synchronisation in Drosophila, CRYPTOCHROME2 was hypothesised as possible light-sensor in Nasonia. Despite being a core clock component, various in vivo and in vitro experiments did not confirm CRYPTOCHROME2 as a light-sensor in Nasonia. The molecular basis of the seasonal response was studied in a set of genetically variable N. vitripennis lines from a single latitudinal location. Lines varied in the proportion of diapausing broods, under short day conditions, indicating variation in the regulation of the seasonal clock, possibly involving other regulatory pathways. This study has provided insight in the molecular regulation of the Nasonia clock and its light synchronisation, information that is important .for understanding how organisms adapt to a cycling environment.