Abstract
Odorant-binding proteins participate in the olfactory system of the honeybee. Apis mellifera ligustica and Apis cerana cerana are species of honeybee that have different biologic functions. The two species have diversified olfactory systems, with A. cerana displaying sensitive olfactory involvement in collecting nectar and pollen from small plants; and A. mellifera collecting from large nectariferous plants. We hypothesized that, given this difference in biologic activity, the gene obp11 of A. mellifera and A. cerana may show different olfactory expression patterns. We cloned and sequenced the obp11 genes from A. mellifera (Amobp11) and A. cerana (Acobp11). Using quantitative real-time PCR, we demonstrated that nurse workers, which have the highest olfactory sensitivity in the A. mellifera hive, have the highest expression of Amobp11; whereas 1-day-emerged workers, which have lowest olfactory sensitivity, have correspondingly low expression. However, the highest expression of Acobp11 is observed for foragers, which display the highest olfactory sensitivity in the A. cerana population. The OBP11 protein from the two species is highly conserved, with an apparent molecular weight and predicted extracellular localization that is similar to other OBP proteins. The expression of the obp11 gene in A. mellifera and A. cerana correlates with the different roles of the olfactory system for the two different species. These findings support the critical role of odorant-binding proteins in the Apis olfactory system
Highlights
For social insects such as the honeybee, olfactory language plays a critical role in colony life, with important functional roles for work within and outside of the hive
We examined whether the obp11 gene expression pattern correlates with the different roles of the olfactory system in A. mellifera and A. cerana, providing a molecular basis for the differences in behavior of the two species
The alignment shows that the two sequences vary in sequence at the C-terminus, which is truncated by 6 cysteine residues for AcOBP11
Summary
For social insects such as the honeybee, olfactory language plays a critical role in colony life, with important functional roles for work within and outside of the hive. Middle-aged bees (12-21 days old) build and maintain the nest, and receive and process nectar (Johnson, 2003, 2008a). After 21 days, workers initiate tasks outside of the nest (foraging nectar and pollen, scouting, defending) (Seeley, 1995; Seeley & Visscher, 2004; Beekman et al, 2006; Visscher, 2007). These behaviors are correlated with the function of the olfactory system, which mediates volatile signals to workers, as opposed to contact perception (Maisonnasse, 2010). Moritz and Crewe suggested that the queen emits volatile pheromones to inhibit new queens or the ovary development of workers (Moritz & Crewe, 1991)
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