Methoprene-tolerant and Krüppel homolog 1 are actors of juvenile hormone-signaling controlling the development of male sexual behavior in the moth Agrotis ipsilon.

In insects, juvenile hormone (JH) is critical for the orchestration of male reproductive maturation. For instance, in the male moth, Agrotis ipsilon, the behavioral response and the neuronal sensitivity within the primary olfactory centers, the antennal lobes (ALs), to the female-emitted sex pheromone increase with fertility during adulthood and the coordination between these events is governed by JH. However, the molecular basis of JH action in the development of sexual behavior remains largely unknown. Here, we show that the expression of the paralogous JH receptors, Methoprene-tolerant 1 and 2 (Met1, Met2) and of the JH-inducible transcription factor, Krüppel homolog 1 (Kr-h1) within ALs raised from the third day of adult life and this dynamic is correlated with increased behavioral responsiveness to sex pheromone. Met1-, Met2- and Kr-h1-depleted sexually mature males exhibited altered sex pheromone-guided orientation flight. Moreover, injection of JH-II into young males enhanced the behavioral response to sex pheromone with increased AL Met1, Met2 and Kr-h1 mRNA levels. By contrast, JH deficiency suppressed the behavioral response to sex pheromone coupled with reduced AL Met1, Met2 and Kr-h1 mRNA levels in allatectomized old males and these inhibitions were compensated by an injection of JH-II in operated males. Our results demonstrated that JH acts through Met-Kr-h1 signaling pathway operating in ALs, to promote the pheromone information processing and consequently the display of sexual behavior in synchronization with fertility to optimize male reproductive fitness. Thus, this study provides insights into the molecular mechanisms underlying the hormonal regulation of reproductive behavior in insects.

Neuroligin 1 expression is linked to plasticity of behavioral and neuronal responses to sex pheromone in the male moth Agrotis ipsilon.

In the moth Agrotis ipsilon, the behavioral response of males to the female-emitted sex pheromone increases throughout adult life and following a prior exposure to sex pheromone, whereas it is temporally inhibited after the onset of mating. This behavioral flexibility is paralleled with changes in neuronal sensitivity to pheromone signal within the primary olfactory centers, the antennal lobes. In the present study, we tested the hypothesis that neuroligins, post-synaptic transmembrane proteins known to act as mediators of neuronal remodeling, are involved in the olfactory modulation in A. ipsilon males. We cloned a full-length cDNA encoding neuroligin 1, which is expressed predominantly in brain and especially in antennal lobes. The level of neuroligin 1 expression in antennal lobes gradually raised from day-2 until day-4 of adult life, as well as at 24 h, 48 h and 72 h following pre-exposure to sex pheromone, and the temporal dynamic of these changes correlated with increased sex pheromone responsiveness. By contrast, there was no significant variation in antennal lobe neuroligin 1 expression during the post-mating refractory period. Taken together, these results highlight that age- and odor experience-related increase in sex pheromone responsiveness is linked to the overexpression of neuroligin 1 in antennal lobes, thus suggesting a potential role played by this post-synaptic cell-adhesion molecule in mediating the plasticity of the central olfactory system in A. ipsilon.

A critical role for Dop1-mediated dopaminergic signaling in the plasticity of behavioral and neuronal responses to sex pheromone in a moth.

Most animal species, including insects, are able to modulate their responses to sexual chemosignals and this flexibility originates from the remodeling of olfactory areas under the influence of the dopaminergic system. In the moth Agrotis ipsilon, the behavioral response of males to the female-emitted sex pheromone increases throughout adult life and after a prior exposure to pheromone signal, and this change is accompanied by an increase in neuronal sensitivity within the primary olfactory centers, the antennal lobes (ALs). To identify the underlying neuromodulatory mechanisms, we examined whether this age- and experience-dependent olfactory plasticity is mediated by dopamine (DA) through the Dop1 receptor, an ortholog of the vertebrate D1-type dopamine receptors, which is positively coupled to adenylyl cyclase. We cloned A. ipsilon Dop1 (AiDop1), which is expressed predominantly in brain and especially in ALs; its knockdown induced a decrease in AL cAMP and altered sex pheromone-orientated flight. The levels of DA, AiDop1 expression and cAMP in ALs increased from the third day of adult life and at 24 and 48 h following pre-exposure to sex pheromone, and the dynamic of these changes correlated with the increased responsiveness to sex pheromone. These results demonstrate that Dop1 is required for the display of male sexual behavior and that age- and experience-related neuronal and behavioral changes are sustained by DA-Dop1 signaling that operates within ALs, probably through cAMP-dependent mechanisms in A. ipsilon Thus, this study expands our understanding of the neuromodulatory mechanisms underlying olfactory plasticity, mechanisms that appear to be highly conserved between insects and mammals.

Involvement of Methoprene-tolerant and Krüppel homolog 1 in juvenile hormone-signaling regulating the maturation of male accessory glands in the moth Agrotis ipsilon.

Male accessory glands (MAGs) produce seminal fluid proteins that are essential for the fertility and also influence the reproductive physiology and behavior of mated females. In many insect species, and especially in the moth Agrotis ipsilon, juvenile hormone (JH) promotes the maturation of the MAGs but the underlying molecular mechanisms in this hormonal regulation are not yet well identified. Here, we examined the role of the JH receptor, Methoprene-tolerant (Met) and the JH-inducible transcription factor, Krüppel homolog 1 (Kr-h1) in transmitting the JH signal that upregulates the growth and synthetic activity of the MAGs in A. ipsilon. We cloned two full length cDNAs encoding Met1 and Met2 which are co-expressed with Kr-h1 in the MAGs where their expression levels increase with age in parallel with the length and protein content of the MAGs. RNAi-mediated knockdown of either Met1, Met2, or Kr-h1 resulted in reduced MAG length and protein amount. Moreover, injection of JH-II into newly emerged adult males induced the transcription of Met1, Met2 and Kr-h1 associated to an increase in the length and protein content of the MAGs. By contrast, JH deficiency decreased Met1, Met2 and Kr-h1 mRNA levels as well as the length and protein reserves of the MAGs of allatectomized old males and these declines were partly compensated by a combined injection of JH-II in operated males. Taken together, our results highlighted an involvement of the JH-Met-Kr-h1 signaling pathway in the development and secretory activity of the MAGs in A. ipsilon.