Impact of disabled circadian clock on yellow fever mosquito Aedes aegypti fitness and behaviors

Abstract

Like other insects, Aedes aegypti displays strong daily patterns in host seeking and mating. Much of these behaviors are believed to be under the control of a circadian clock, an endogenous timekeeping mechanism relying on transcriptional/translational negative feedback loops that drive rhythmic physiology and behavior. To examine the connection between the circadian clock and various Ae. aegypti behaviors, we knocked out the core clock gene cycle using CRISPR/Cas9. We found that the rhythmic pattern and intensity of mRNA expression of seven circadian genes, including AeCyc−/−, were altered across the day/night cycle as well as in constant darkness conditions. We further show that the mutant CYC protein is incapable of forming a dimer with CLK to stimulate per expression and that the endogenous clock is disabled in AeCyc−/− mosquitoes. AeCyc−/− do not display the bimodal locomotor activity pattern of wild type, have a significantly reduced response to host odor, reduced egg hatching rates, delayed embryonic development and reduced adult survival and mating success. Surprisingly however, the propensity to blood feed in AeCyc−/− females is significantly higher than in wildtype females. Together with other recent work on the circadian clock control of key aspects of mosquito biology, our data on how cycle KO affects mosquito behavior and fitness provides a basis for further work into the pathways that connect the mosquito endogenous clock to its vector competence.

Molecular correlates of swarming behaviour inAedes aegyptimales

“…In our study, we did not detect differential expression of canonical clock genes during swarming. However, concluding that the clock is not involved in swarming may be premature as both Anopheles and Aedes show a reduction in mating and fertility when the clock is disrupted [21,35], indicating that many processes are affected. Additionally, it is notable that slowpoke ( slo ) was upregulated in swarming males.…”

Behavioral rhythms are bad predictors of general organismal rhythmicity

“…Control of diel rhythmicity by circadian clocks is a major factor shaping a species‟ adaptations to its cyclic environment and can thus strongly affect fitness [10,11,56,57]. According to the classical view, endogenous clocks help to anticipate cycles and optimize timing to maximize resource usage and minimize predation risk.…”

“…Diversity of rhythmic phenotypes, even among closely related individuals, is ubiquitous in animals. However, especially for "non-conventional" but evolutionary and ecological Control of diel rhythmicity by circadian clocks is a major factor shaping a species" adaptations to its cyclic environment and can thus strongly affect fitness [10,11,56,57].…”

Clock genes regulate mating activity rhythms in the vector mosquitoes, Aedes albopictus and Culex quinquefasciatus

“…For mosquito disease vectors, clock genes expression and locomotor activity rhythms are welldocumented [38][39][40]. Furthermore, some clock genes, such as per, tim and cyc have been found to be involved in locomotor activity, mating or blood feeding behaviors [21,22,41,42]. However, the complete molecular clock mechanisms of mosquitoes and how they regulate various behaviors requires further study.…”

“…In Ae . aegypti , knockout of cyc was found to reduced mating success [ 22 ]. However, it remains unclear how the molecular clocks regulate the mating behavior rhythm in Ae .…”