Abstract
Leaf-cutting ants are evolutionary derived social insects with elaborated division of labor and tremendous colony sizes with millions of workers. Their social organization is mainly based on olfactory communication using different pheromones and is promoted by a pronounced size-polymorphism of workers that perform different tasks within the colony. The size polymorphism and associated behaviors are correlated to distinct antennal lobe (AL) phenotypes. Two worker phenotypes differ in number of olfactory glomeruli in the AL and the presence or absence of an extremely large glomerulus (macroglomerulus), involved in trail-pheromone reception. The males' AL contains three macroglomeruli which are presumably involved in detection of sex-pheromone components. We investigated the antennal transcriptome data of all major castes (males, queens and workers) and two worker subcastes (large and tiny workers). In order to identify putative odorant receptor genes involved in pheromone detection, we identified differentially expressed odorant receptor genes (OR-genes) using custom microarrays. In total, we found 185 OR-gene fragments that are clearly related to ORs and we identified orthologs for 70 OR-genes. Among them one OR-gene differs in relative expression between the two worker subcastes by a factor of >3 and thus is a very promising candidate gene for the trail-pheromone receptor. Using the relative expression of OR-genes in males versus queens, we identified 2 candidates for sex-pheromone receptor genes in males. In addition, we identified genes from all other chemosensory related gene families (13 chemosensory protein genes, 8 odorant binding protein genes, 2 sensory-neuron membrane protein genes, 7 ionotropic receptor genes, 2 gustatory receptor genes), and we found ant-specific expansions in the chemosensory protein gene family. In addition, a large number of genes involved in immune defense exhibited differential expression across the three different castes, and some genes even between the two worker subcastes.
Highlights
The family of ants (Formicidae) contains over 12 000 described species, with tremendous global diversity; ants contribute to more than half of the total insect biomass [1]
Pooled cDNA from queens, males and workers of A. vollenweideri was used as a template for Illumina Solexa and Roche 454 FLX sequencing, generating 4,4 billion bases of information (Table 1)
From the data we conclude that on an abstract level as described by GO annotation, the antennal markup of A. vollenweideri is comparable to similar transcriptome datasets in other insect species, for example the Lepidoptera Manduca sexta [44] and Spodoptera litoralis [56]
Summary
The family of ants (Formicidae) contains over 12 000 described species, with tremendous global diversity; ants contribute to more than half of the total insect biomass [1]. In particular during nest foundation, queens are not protected by the social immune system of the colony and foraging workers are probably more exposed to pathogens than the tiny workers that are exclusively involved in fungus cultivation [7]. Such pronounced differences in behavioral repertoirs and lifehistories are probably supported by distinct expression patterns of many genes, including immune genes (for review focusing on social immune systems see Cremer et al [8])
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
