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.

Community acquired-methicillin resistant Staphylococcus aureus (CA-MRSA) is a socially problematic pathogen that infects healthy individuals, causing severe disease. CA-MRSA is more virulent than hospital associated-MRSA (HA-MRSA). The underlying mechanism for the high virulence of CA-MRSA is not known. The transcription product of the psm-mec gene, located in the mobile genetic element SCCmec of HA-MRSA, but not CA-MRSA, suppresses the expression of phenol-soluble modulin α (PSMα), a cytolytic toxin of S. aureus. Here we report that psm-mec RNA inhibits translation of the agrA gene encoding a positive transcription factor for the PSMα gene via specific binding to agrA mRNA. Furthermore, 25% of 325 clinical MRSA isolates had a mutation in the psm-mec promoter that attenuated transcription, and 9% of the strains had no psm-mec. In most of these psm-mec-mutated or psm-mec-deleted HA-MRSAs, PSMα expression was increased compared with strains carrying intact psm-mec, and some mutated strains produced high amounts of PSMα comparable with that of CA-MRSA. Deletion of psm-mec from HA-MRSA strains carrying intact psm-mec increased the expression of AgrA protein and PSMα, and virulence in mice. Thus, psm-mec RNA suppresses MRSA virulence via inhibition of agrA translation and the absence of psm-mec function in CA-MRSA causes its high virulence property.

To identify candidate genes involved in the aggressive behavior of worker honeybees, we used the differential display method to search for RNAs exclusively detected in the brains of aggressive workers that had attacked a hornet. We identified a novel, 10,152-nucleotide RNA, termed Kakugo RNA. Kakugo RNA encodes a protein of 2,893 amino acid residues that shares structural features and sequence similarities with various picorna-like virus polyproteins, especially those from sacbrood virus, which infects honeybees. The Kakugo protein contains several domains that correspond to the virion protein, helicase, protease, and RNA-dependent RNA polymerase domains of various picorna-like virus polyproteins. When the worker bee tissue lysate was subjected to sucrose density gradient centrifugation, Kakugo RNA, except for the material at the bottom, was separated into two major peaks. One of the peaks corresponded to the position of Kakugo mRNA, and the other corresponded to the position of the poliovirus virion. These results suggest that the Kakugo RNA exists as an mRNA-like free RNA and virion RNA in the honeybee. Furthermore, injection of the lysate supernatant from the attacker heads into the heads of noninfected bees resulted in a marked increase in Kakugo RNA. These results demonstrate that Kakugo RNA is a plus-strand RNA of a novel picorna-like virus and that the brains of aggressive workers are infected by this novel virus. Kakugo RNA was detected in aggressive workers but not in nurse bees or foragers. In aggressive workers, Kakugo RNA was detected in the brain but not in the thorax or abdomen, indicating a close relation between viral infection in the brain and aggressive worker behaviors.The European honeybee Apis mellifera L. is a eusocial insect, and the workers perform diverse tasks to maintain colony activity, such as comb-building, nursing, guarding, and foraging, according to age after eclosion (age polyethism) (36). Guard bees gathering at the entrance of the hive are highly aggressive and often scramble to counterattack natural enemies, such as hornets, to protect the colony (4, 5). The worker honeybee stinger is part of a highly modified ovipositor that evolved for defensive functions. The stinger is hooked and the worker loses it after use, resulting in the death of the bee. The advantage of losing the stinger is that the venom sac is then activated to inject additional venom after the sac detaches from the abdomen of the workers. The attacking behavior of guard bees is self-sacrificing and is therefore considered to be a typical altruistic behavior exhibited by the workers (35). Thus, the honeybee is an attractive model for the study of altruistic aggressive behaviors. Quantitative trait locus analysis has been used to identify the loci related to aggressive worker behaviors (11, 12). The genes responsible for the aggressive behaviors, however, have not yet been identified.Previously, members of our laboratories used the differential display method to identify genes expressed preferentially in the mus...

We used a cDNA microarray to identify genes expressed in a caste (worker)-and division of labor (nurse bees or foragers)-dependent manner in the honeybee brain. Among the identified genes, one encoded a putative orphan receptor (HR38) homologue that mediates ecdysteroid-signaling. Realtime reverse transcription-polymerase chain reaction indicated that expression of this gene is higher in forager brains, as compared to nurse bees and queens. In the forager brain, expression was concentrated in a subset of the mushroom body neurons, suggesting that ecdysteroid-signaling in the mushroom bodies might be involved in the division of labor of the workers.

Carbohydrate-metabolizing enzymes may have particularly interesting roles in the honey bee, Apis mellifera , because this social insect has an extremely carbohydrate-rich diet, and nutrition plays important roles in caste determination and socially mediated behavioural plasticity. We annotated a total of 174 genes encoding carbohydrate-metabolizing enzymes and 28 genes encoding lipid-metabolizing enzymes, based on orthology to their counterparts in the fly, Drosophila melanogaster, and the mosquito, Anopheles gambiae . We found that the number of genes for carbohydrate metabolism appears to be more evolutionarily labile than for lipid metabolism. In particular, we identified striking changes in gene number or genomic organization for genes encoding glycolytic enzymes, cellulase, glucose oxidase and glucose dehydrogenases, glucosemethanol-choline (GMC) oxidoreductases, fucosyltransferases, and lysozymes.

Mushroom bodies (MBs) are considered to be involved in higher-order sensory processing in the insect brain. To identify the genes involved in the intrinsic function of the honeybee MBs, we searched for genes preferentially expressed therein, using the differential display method. Here we report a novel gene encoding a putative transcription factor (Mblk-1) expressed preferentially in one of two types of intrinsic MB neurones, the large-type Kenyon cells, which makes Mblk-1 a candidate gene involved in the advanced behaviours of honeybees. A putative DNA binding motif of Mblk-1 had significant sequence homology with those encoded by genes from various animal species, suggesting that the functions of these proteins in neural cells are conserved among the animal kingdom.

The mushroom bodies (a higher center) of the honeybee (Apis mellifera L) brain were considered to comprise three types of intrinsic neurons, including large- and small-type Kenyon cells that have distinct gene expression profiles. Although previous neural activity mapping using the immediate early gene kakusei suggested that small-type Kenyon cells are mainly active in forager brains, the precise Kenyon cell types that are active in the forager brain remain to be elucidated. We searched for novel gene(s) that are expressed in an area-preferential manner in the honeybee brain. By identifying and analyzing expression of a gene that we termed mKast (middle-type Kenyon cell-preferential arrestin-related protein), we discovered novel ‘middle-type Kenyon cells’ that are sandwiched between large- and small-type Kenyon cells and have a gene expression profile almost complementary to those of large– and small-type Kenyon cells. Expression analysis of kakusei revealed that both small-type Kenyon cells and some middle-type Kenyon cells are active in the forager brains, suggesting their possible involvement in information processing during the foraging flight. mKast expression began after the differentiation of small- and large-type Kenyon cells during metamorphosis, suggesting that middle-type Kenyon cells differentiate by modifying some characteristics of large– and/or small-type Kenyon cells. Interestingly, CaMKII and mKast, marker genes for large– and middle-type Kenyon cells, respectively, were preferentially expressed in a distinct set of optic lobe (a visual center) neurons. Our findings suggested that it is not simply the Kenyon cell-preferential gene expression profiles, rather, a ‘clustering’ of neurons with similar gene expression profiles as particular Kenyon cell types that characterize the honeybee mushroom body structure.

To clarify the molecular basis underlying the neural function of the honeybee mushroom bodies (MBs), we identified three genes preferentially expressed in MB using cDNA microarrays containing 480 differential display-positive candidate cDNAs expressed locally or differentially, dependent on caste/aggressive behavior in the honeybee brain. One of the cDNAs encodes a putative type I inositol 1,4,5-trisphosphate (IP 3 ) 5-phosphatase and was expressed preferentially in one of two types of intrinsic MB neurons, the large-type Kenyon cells, suggesting that IP 3 -mediated Ca 2+ signaling is enhanced in these neurons. ß