Chronobiological plasticity in Honeybee and its association with differences in the organization of the molecular pathway between central and peripheral clocks: the brain and flight muscle tissues.

Abstract

Circadian rhythms govern the behavior, physiology, and metabolism of living organisms, enabling them to anticipate changes of environmental conditions. Within Insects, in honey bee s colonies an ontogeny in circadian rhythms of behavior was suggested to be related to an age- based division of labor, to best serve their social organization: young adult tend to perform tasks in the nest, nursing brood around the clock, with no circadian rhythms for the 2 3 first weeks, and then shift to foraging outside for the remainder period of life, enabling visiting flowers at time of maximal nectar and pollen availability. In addition to light, social cues is one of the primary zeitgeber that entrain the locomotor activity rhythm in honeybees, as notably showed by the robustness of circadian activity of young nurses soon after their release far from social interactions with the conspecifics. Such context dependent plasticity in circadian behavior was often associated with a variation in the main core clock genes mRNA expression profile in the brain, but it has not been yet examined whether such variations extend to other body tissues of the honeybee. In this thesis, I identified for the first time oscillating transcription of core clock genes in the flight muscle of workers, which temporal cycling pattern differed significantly in LD and under DD, in a task rather than age dependent manner. Although the autonomy of such oscillator from central orchestration has yet to be determined, the consistent temporal cycling pattern of mRNA level enriched for genes highly involved in muscle metabolism, suggest exciting future opportunities to discover additional clock controlled genes in the honeybee. The ensemble of progresses, might give answer to the kind of relationships between different clocks, involving eventually total and partial autonomy, especially in such an excellent model in chronobiology: the Honeybee.