Differential regulation of the <it>foraging </it>gene associated with task behaviors in harvester ants

<p>Abstract</p> <p>Background</p> <p>The division of labor in social insect colonies involves transitions by workers from one task to another and is critical to the organization and ecological success of colonies. The differential regulation of genetic pathways is likely to be a key mechanism involved in plasticity of social insect task behavior. One of the few pathways implicated in social organization involves the cGMP-activated protein kinase gene, <it>foraging</it>, a gene associated with <it>foraging</it> behavior in social insect species. The association of the <it>foraging </it>gene with behavior is conserved across diverse species, but the observed expression patterns and proposed functions of this gene vary across taxa. We compared the protein sequence of <it>foraging </it>across social insects and explored whether the differential regulation of this gene is associated with task behaviors in the harvester ant, <it>Pogonomyrmex occidentalis</it>.</p> <p>Results</p> <p>Phylogenetic analysis of the coding region of the <it>foraging </it>gene reveals considerable conservation in protein sequence across insects, particularly among hymenopteran species. The absence of amino acid variation in key active and binding sites suggests that differences in behaviors associated with this gene among species may be the result of changes in gene expression rather than gene divergence. Using real time qPCR analyses with a harvester ant ortholog to <it>foraging </it>(<it>Pofor</it>), we found that the brains of harvester ant foragers have a daily fluctuation in expression of <it>foraging </it>with mRNA levels peaking at midday. In contrast, young workers inside the nest have low levels of <it>Pofor </it>mRNA with no evidence of daily fluctuations in expression. As a result, the association of <it>foraging </it>expression with task behavior within a species changes depending on the time of day the individuals are sampled.</p> <p>Conclusions</p> <p>The amino acid protein sequence of <it>foraging </it>is highly conserved across social insects. Differences in foraging behaviors associated with this gene among social insect species are likely due to differences in gene regulation rather than evolutionary changes in the encoded protein. The task-specific expression patterns of <it>foraging </it>are consistent with the task-specific circadian rhythms observed in harvester ants. Whether the molecular clock plays a role in regulating <it>foraging </it>gene expression (or vice versa) remains to be determined. Our results represent the first time series analysis of <it>foraging </it>gene expression and underscore the importance of assaying time-related expression differences in behavioral studies. Understanding how this gene is regulated within species is critical to explaining the mechanism by which <it>foraging </it>influences behavior.</p>

Abstract licence: CC BY

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