Here we report the genome sequence of the honeybee Apis mellifera, a key model for social behaviour and essential to global ecology through pollination. Compared with other sequenced insect genomes, the A. mellifera genome has high A+T and CpG contents, lacks major transposon families, evolves more slowly, and is more similar to vertebrates for circadian rhythm, RNA interference and DNA methylation genes, among others. Furthermore, A. mellifera has fewer genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, more genes for odorant receptors, and novel genes for nectar and pollen utilization, consistent with its ecology and social organization. Compared to Drosophila, genes in early developmental pathways differ in Apis, whereas similarities exist for functions that differ markedly, such as sex determination, brain function and behaviour. Population genetics suggests a novel African origin for the species A. mellifera and insights into whether Africanized bees spread throughout the New World via hybridization or displacement.

In most animals, longevity is achieved at the expense of fertility, but queen honey bees do not show this tradeoff. Queens are both long-lived and fertile, whereas workers, derived from the same genome, are both relatively short-lived and normally sterile. It has been suggested, on the basis of results from workers, that vitellogenin (Vg), best known as a yolk protein synthesized in the abdominal fat body, acts as an antioxidant to promote longevity in queen bees. We explored this hypothesis, as well as related roles of insulin-IGF-1 signaling and juvenile hormone. Vg was expressed in thorax and head fat body cells in an age-dependent manner, with old queens showing much higher expression than workers. In contrast, Vg expression in worker head was much lower. Queens also were more resistant to oxidative stress than workers. These results support the hypothesis that caste-specific differences in Vg expression are involved in queen longevity. Consistent with predictions from Drosophila, old queens had lower head expression of insulin-like peptide and its putative receptors than did old workers. Juvenile hormone affected the expression of Vg and insulin-IGF-1 signaling genes in opposite directions. These results suggest that conserved and species-specific mechanisms interact to regulate queen bee longevity without sacrificing fecundity.Apis mellifera ͉ lifespan ͉ social insect H oney bees (Apis mellifera) provide an attractive model to identify the molecular mechanisms regulating variation in lifespan. Workers and queens develop from the same genome, but queen lifespan is Ϸ10-fold longer (1). Moreover, queen longevity is achieved without the typical tradeoff between longevity and reproduction. Queens lay up to 2,000 eggs per day (2) and live for 1-3 years. Workers, in contrast, have limited fecundity and live for 3-6 weeks during spring and summer in temperate climates (1).Insulin-IGF-1 signaling (IIS) is a key integrative pathway regulating aging, fertility and other important biological processes in vertebrates and invertebrates. Down-regulation of IIS is associated with increased longevity and decreased fertility in Caenorhabditis elegans and Drosophila melanogaster (3). Although IIS functions are widely conserved, it is not known whether naturally occurring differences in longevity also are a result of variation in this pathway.Recent advances in insect molecular endocrinology have revealed connections between IIS and juvenile hormone (JH), a major insect hormone with diverse influences on growth, reproduction, and longevity in many species (4). Studies with Drosophila point to a connection between IIS and JH (5, 6). Because queens are both long-lived and reproductively active, the unique relationship between JH and vitellogenin (Vg) in honey bees has attracted attention (7). Honey bee Vg is a 180-kDa glycolipoprotein (8) synthesized in fat body cells and released to the hemolymph. Vg is best known as a yolk protein and is taken up by developing oocytes (9). JH is a gonadotropin and regulates vitellogenesis in ...

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The nuclear receptors (NRs) of metazoans are an ancient family of transcription factors defined by conserved DNA- and ligand-binding domains (DBDs and LBDs, respectively). The Drosophila melanogaster genome project revealed 18 canonical NRs (with DBDs and LBDs both present) and 3 receptors with the DBD only. Annotation of subsequently sequenced insect genomes revealed only minor deviations from this pattern. A renewed focus on functional analysis of the isoforms of insect NRs is therefore required to understand the diverse roles of these transcription factors in embryogenesis, metamorphosis, reproduction, and homeostasis. One insect NR, ecdysone receptor (EcR), functions as a receptor for the ecdysteroid molting hormones of insects. Researchers have developed nonsteroidal ecdysteroid agonists for EcR that disrupt molting and can be used as safe pesticides. An exciting new technology allows EcR to be used in chimeric, ligand-inducible gene-switch systems with applications in pest management and medicine.

Previous research has led to the idea that derived traits can arise through the evolution of novel roles for conserved genes. We explored whether Neuropeptide Y-like signaling, a conserved pathway that regulates food-related behavior, is involved in a derived, nutritionally-related trait, division of labor in worker honey bees. Transcripts encoding two NPY-like peptides were expressed in separate populations of brain neurosecretory cells, consistent with endocrine functions. NPY-related genes were upregulated in the brains of older foragers compared to younger bees performing brood care ("nurses"). A subset of these changes can be attributed to nutrition, but NPF peptide treatments did not influence sugar intake. These results contrast with recent reports of more robust associations between division of labor and the related insulinsignaling pathway and suggest that some elements of molecular pathways associated with feeding behavior may be more evolutionarily labile than others.

The Drosophila genome encodes 18 canonical nuclear receptors. All of the Drosophila nuclear receptors are here shown to be present in the genome of the honey bee ( Apis mellifera ). Given that the time since divergence of the Drosophila and Apis lineages is measured in hundreds of millions of years, the identification of matched orthologous nuclear receptors in the two genomes reveals the fundamental set of nuclear receptors required to 'make' an endopterygote insect. The single novelty is the presence in the A. mellifera genome of a third insect gene similar to vertebrate photoreceptor-specific nuclear receptor (PNR). Phylogenetic analysis indicates that this novel gene, which we have named AmPNR -like, is a new member of the NR2 subfamily not found in the Drosophila or human genomes. This gene is expressed in the developing compound eye of the honey bee. Like their vertebrate counterparts, arthropod nuclear receptors play key roles in embryonic and postembryonic development. Keywords: Apis mellifera , photoreceptor cell specific nuclear receptor, seven-up, steroid hormone receptor, ultraspiracle. IntroductionNuclear receptors constitute a protein superfamily that can be recognized in metazoans as distantly related as jellyfish and humans by the presence of highly conserved Nterminal DNA-binding domains (DBD) with 2 C4 zinc fingers (Robinson-Rechavi & Laudet, 2003). Nuclear receptor superfamily members also contain a conserved C-terminal ligand-binding domain (LBD) that is less conserved than the defining DBD. The variable LBD region of nuclear receptor proteins contains a ligand-binding pocket and a dimerization domain, plus regions that interact with cofactors serving as transcriptional intermediary factors (Moras & Gronemeyer, 1998).Many nuclear receptors regulate transcription via transduction of signals from small, lipophilic molecules such as steroid hormones (Carson-Jurica et al ., 1990;Tsai & O'Malley, 1994). Other nuclear receptor family members, identified on the basis of DBD homology, do not (or did not when they were initially described) have known ligands. They are therefore referred to as orphan receptors (Giguere, 1999). Phylogenetic analysis demonstrates that the earliest members of the nuclear receptor family were the so-called orphans and that ligand-binding capacity was acquired later in animal evolution (Escriva et al ., 1997;Bertrand et al ., 2004).The 49 nuclear receptors identified in the human genome include receptors for the steroid hormones, thyroid

In this study, we cloned and characterized three Manduca sexta odorant receptors (ORs). One receptor is a putative pheromone receptor expressed exclusively in a cell associated with male-specific type-I trichoid sensilla. We describe the results of real-time PCR (RT-PCR) and quantitative real-time PCR (qRT-PCR) experiments that show MsextaOR1 is expressed only in male antennae. In situ hybridization labels a single cell associated with type-1 trichoid sensilla, which houses two neurons that have been previously determined to respond to the major components of the pheromone blend. The second receptor, MsextaOR2, was discovered using degenerate primers designed to conserved motifs of a unique group ORs that share as much as 88% identity. Comparison of RT-PCR, qRT-PCR, and in situ hybridization results with those of ORs in the Drosophila melanogaster Or83b subfamily shows a strong sequence and expression pattern similarity. The third receptor, MsextaOR3, was found by 5'-end sequencing of a normalized and subtracted cDNA library from male M. sexta antennae. RT-PCR and qRT-PCR show that this receptor is expressed only in male and female antennae. These are the first ORs, including a putative pheromone receptor, to be described from M. sexta.

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