Size-dependent <it>foraging </it>gene expression and behavioral caste differentiation in <it>Bombus ignitus</it>

• Main Authors: Yokoyama Jun, Ohtsuki Hajime, Kodaira Yosuke, Kawata Masakado
• Format: Article
• Language: English
• Published: BMC 2009-09-01
• Series: BMC Research Notes
• Online Access: http://www.biomedcentral.com/1756-0500/2/184

<p>Abstract</p> <p>Background</p> <p>In eusocial hymenopteran insects, <it>foraging </it>genes, members of the cGMP-dependent protein kinase family, are considered to contribute to division of labor through behavioral caste differentiation. However, the relationship between <it>foraging </it>gene expression and behavioral caste in honeybees is opposite to that observed in ants and wasps. In the previously examined eusocial Hymenoptera, workers behave as foragers or nurses depending on age. We reasoned that examination of a different system of behavioral caste determination might provide new insights into the relationship between <it>foraging </it>genes and division of labor, and accordingly focused on bumblebees, which exhibit size-dependent behavioral caste differentiation. We characterized a <it>foraging </it>gene (<it>Bifor</it>) in bumblebees (<it>Bombus ignitus</it>) and examined the relationship between <it>Bifor </it>expression and size-dependent behavioral caste differentiation.</p> <p>Findings</p> <p>A putative open reading frame of the <it>Bifor </it>gene was 2004 bp in length. It encoded 668 aa residues and showed high identity to orthologous genes in other hymenopterans (85.3-99.0%). As in ants and wasps, <it>Bifor </it>expression levels were higher in nurses than in foragers. <it>Bifor </it>expression was negatively correlated with individual body size even within the same behavioral castes (regression coefficient = -0.376, P < 0.001, all individuals; -0.379, <it>P </it>= 0.018, within foragers).</p> <p>Conclusion</p> <p>These findings indicate that <it>Bifor </it>expression is size dependent and support the idea that <it>Bifor </it>expression levels are related to behavioral caste differentiation in <it>B. ignitus</it>. Thus, the relationship between <it>foraging </it>gene expression and behavioral caste differentiation found in ants and wasps was identified in a different system of labor determination.</p>