An Antennal Circadian Clock and Circadian Rhythms in Peripheral Pheromone Reception in the Moth Spodoptera littoralis

Abstract

Circadian rhythms are observed in mating behaviors in moths: females emit sex pheromones and males are attracted by these pheromones in rhythmic fashions. In the moth Spodoptera littoralis, we demonstrated the occurrence of a circadian oscillator in the antenna, the peripheral olfactory organ. We identified different clock genes, period (per), cryptochrome1 (cry1) and cryptochrome2 (cry2), in this organ. Using quantitative real-time PCR (qPCR), we found that their corresponding transcripts cycled circadianly in the antenna as well as in the brain. Electroantennogram (EAG) recordings over 24 h demonstrated for the first time a circadian rhythm in antennal responses of a moth to sex pheromone. qPCR showed that out of one pheromone-binding protein (PBP), one olfactory receptor (OR), and one odorant-degrading enzyme (ODE), all putatively involved in the pheromone reception, only the ODE transcript presented a circadian rhythm that may be related to rhythms in olfactory signal resolution. Peripheral or central circadian clock control of olfaction is then discussed in light of recent data.

Age and Mating Status Do Not Affect Transcript Levels of Odorant Receptor Genes in Male Antennae of Heliothis virescens and Heliothis subflexa

“…Our current work and that of Merlin et al (2007) and Zhang et al (2009) are a first step in this direction, but before any overall assessment of this relationship can be arrived at there is a need for similar gene expression studies in other moth species over the majority of their life spans.…”

“…In H. virescens, only one study has examined odorant receptor expression in male antennae at different times during pupal development (Krieger et al, 2009). A study that examined expression of one odorant receptor and one pheromone binding protein at nine time points during a 24 h period post eclosion in Spodoptera littoralis male antennae (Merlin et al, 2007) found no drastic changes in transcript abundance throughout this period of time. Another study that measured the effects of both age and (Zhang et al, 2009), found that both factors affected expression levels of the pheromone binding protein gene, PxylPBP1.…”

Two sides of a coin: ecological and chronobiological perspectives of timing in the wild

“…Other examples are responses to olfactory cues. Thus, the male moth antenna responds differentially to a similar dose of female sex attractants delivered at different times of day [104], and tadpoles respond differently when exposed during the day or night to the same concentration of chemical cues of their predator [105].…”

Perfusion with cAMP analogue affects pheromone-sensitive trichoid sensilla of the hawkmothManduca sextain a time-dependent manner

“…In addition, our results suggest that circadian changes in odour sensitivity in moths are also regulated at the periphery as they are in D. melanogaster (Tanoue et al, 2004;Krishnan et al, 2008), cockroaches (Saifullah and Page, 2009) and other moths (Merlin et al, 2007). The endogenous decline in the mean SP amplitude, AP frequency, and the spontaneous AP activity during the photophase suggests that the observed circadian rhythms in pheromone sensitivity are at least partly due to time-dependent regulation of single ORNs.…”