Abstract
Aphids respond to specific environmental cues by producing alternative morphs, a phenomenon called polyphenism, but also by modulating their individual behavior even within the same morph. This complex plasticity allows a rapid adaptation of individuals to fluctuating environmental conditions, but the underlying genetic and molecular mechanisms remain largely unknown. The foraging gene is known to be associated with behavior in various species and has been shown to mediate the behavioral shift induced by environmental changes in some insects. In this study, we investigated the function of this gene in the clonal forms of the pea aphid Acyrthosiphon pisum by identifying and cloning cDNA variants, as well as analyzing their expression levels in developmental morphs and behavioral variants. Our results indicate that the expression of foraging changes at key steps of the aphid development. This gene is also highly expressed in sedentary wingless adult morphs reared under crowded conditions, probably just before they start walking and foraging. The cGMP-dependent protein kinase (PKG) enzyme activity measured in the behavioral variants correlates with the level of foraging expression. Altogether, our results suggest that foraging could act to promote the shift from a sedentary to an exploratory behavior, being thus involved in the behavioral plasticity of the pea aphid.
Highlights
Aphids are insects which respond quickly to environmental changes by developing alternative phenotypes, such as asexual and sexual forms, a phenomenon called polyphenism
Thanks to the recent sequencing of the pea aphid genome, we managed to locate these two complete A. pisum for cDNAs on a genomic scaffold (Scaffold409, GeneBank accession number GL350029) and subsequently deduced that they are composed of 16 exons, exons 3 to 16 being common to Apfor1 and Apfor2 (Figure 1)
We report the cloning and analysis of the transcripts of this gene in the pea aphid Acyrthosiphon pisum, a interesting species regarding its polyphenism ability combined with behavioral plasticity, allowing rapid adaptation to unfavorable environmental conditions, such as overcrowding or the presence of enemies
Summary
Aphids are insects which respond quickly to environmental changes by developing alternative phenotypes, such as asexual and sexual forms, a phenomenon called polyphenism. Some aphids leave their host plant and begin to explore their close environment to find fresh resources and to immediately settle new colonies [3,4] The release of volatile compounds, such as the alarm pheromone secreted by aphids in the presence of predators, triggers various reactions such as the withdrawal of the stylet from the plant, or the walking or dropping off the host plant [5]. This high behavioral plasticity makes them good candidates to explore the molecular basis of such a phenomenon. Almost nothing is known of the physiological and genetic mechanisms controlling polyphenism and individual behavior in aphids [6,7]
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