Meeting Abstract
Avian seasonal breeding has long been tied to the seasonal change in photoperiod in a number of temperate zone species. Unlike mammals, detection of light cues has been shown to occur independent of both the eyes and pineal glands via extra-retinal photoreceptive opsins located in the medial basal hypothalamus. To date, the precise identity of the specific opsin types and populations responsible for the photoinduction of seasonal breeding remains unresolved. Based on brain localization and light spectra profiles two potential candidates have emerged for the detection of light cues with respect to breeding; Neuropsin (Opn5) and Vertebrate Ancient Opsin (VA-opsin). Utilizing recent developments in viral vector technology we have silenced Opn5 and VA-opsin expression independently and together in the medial basal hypothalamus of Japanese Quail (Coturnix japonica) prior to photostimulation by long days (18L:6D). Body weight and cloacal gland volume was measured weekly for 4 weeks following photostimulation, a period sufficient for un-manipulated animals to reach reproductive condition. We found that RNA inhibition of Opn5 or Both showed an increase in mass gain rate when compared to VA only and control individuals. All three silencing treatments (Opn5, VA, Both) displayed reduced rates of cloacal gland growth (K) compared to control birds suggesting opsin silencing decreased the rate of hypothalamus-pituitary- gonadal (HPG) axis activation. Our data suggest that both Opn5 and VA-opsin play a key role in the activation of the reproductive axis in response to photostimulation and seasonal mass gain may be controlled via partially independent pathways from the HPG axis. Research was funded by the Leverhulme Trust and BBSRC (BB/P013759/1).
