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Susan E Fahrbach

Publications and source records attributed to Susan E Fahrbach.

13 recordsLinked to original sources
PubMed2006

Nuclear receptors of the honey bee: annotation and expression in the adult brain.

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. Studies in Drosophila have focused primarily on the role of these transcription factors in embryogenesis and metamorphosis. Examination of an expressed sequence tag library developed from the adult bee brain and analysis of transcript expression in brain using in situ hybridization and quantitative RT-PCR revealed that several members of the nuclear receptor family (AmSVP, AmUSP, AmERR, AmHr46, AmFtz-F1, and AmHnf-4) are expressed in the brain of the adult bee. Further analysis of the expression of AmUSP and AmSVP in the mushroom bodies, the major insect brain centre for learning and memory, revealed changes in transcript abundance and, in the case of AmUSP, changes in transcript localization, during the development of foraging behaviour in the adult. Study of the honey bee therefore provides a model for understanding nuclear receptor function in the adult brain.

Amino Acid Sequence↗
PubMed2006

Structure of the mushroom bodies of the insect brain.

The past decade has produced an explosion of new information on the development, neuroanatomy, and possible functions of the mushroom bodies. This review provides a concise, contemporary overview of the structure of the mushroom bodies. Two topics are highlighted: the volume plasticity of mushroom body neuropils evident in the brains of some adult insects and a possible essential role for the gamma lobe in olfactory memory.

Adenylyl Cyclases↗
PubMed2005

Stimulation of muscarinic receptors mimics experience-dependent plasticity in the honey bee brain.

Honey bees begin life working in the hive. At approximately 3 weeks of age, they shift to visiting flowers to forage for pollen and nectar. Foraging is a complex task associated with enlargement of the mushroom bodies, a brain region important in insects for certain forms of learning and memory. We report here that foraging bees had a larger volume of mushroom body neuropil than did age-matched bees confined to the hive. This result indicates that direct experience of the world outside the hive causes mushroom body neuropil growth in bees. We also show that oral treatment of caged bees with pilocarpine, a muscarinic agonist, induced an increase in the volume of the neuropil similar to that seen after a week of foraging experience. Effects of pilocarpine were blocked by scopolamine, a muscarinic antagonist. Our results suggest that signaling in cholinergic pathways couples experience to structural brain plasticity.

Analysis of Variance↗
PubMed2005

Pteropsin: a vertebrate-like non-visual opsin expressed in the honey bee brain.

Insects have excellent color vision based on the expression of different opsins in specific sets of photoreceptive cells. Opsins are members of the rhodopsin superfamily of G-protein coupled receptors, and are transmembrane proteins found coupled to light-sensitive chromophores in animal photoreceptors. Diversification of opsins during animal evolution provided the basis for the development of wavelength-specific behavior and color vision, but with the exception of the recently discovered non-visual melanopsins, vertebrate and invertebrate opsins have generally been viewed as representing distinct lineages. We report a novel lineage of insect opsins, designated pteropsins. On the basis of sequence analysis and intron location, pteropsins are more closely related to vertebrate visual opsins than to invertebrate opsins. Of note is that the pteropsins are missing entirely from the genome of drosophilid flies. In situ hybridization studies of the honey bee, Apis mellifera, revealed that pteropsin is expressed in the brain of this species and not in either the simple or compound eyes. It was also possible, on the basis of in situ hybridization studies, to assign different long wavelength opsins to the compound eyes (AmLop1) and ocelli (AmLop2). Insect pteropsin might be orthologous to a ciliary opsin recently described from the annelid Platynereis, and therefore represents the presence of this vertebrate-like light-detecting system in insects.

Animals↗
PubMed2005

"Neuroethoendocrinology": integration of field and laboratory studies in insect neuroendocrinology.

Progress in the field of insect neuroendocrinology has been rapid despite the relatively small number of investigators working on insect systems. This progress, in part, reflects the ease of studying insect behavior in the laboratory, and a historical perspective reveals that insect neuroendocrinology has been dominated since its inception by laboratory studies. Recent advances in methodology and a renewed interest in the concept of behavioral state in insects suggest that it might be useful for insect neuroendocrinologists to spend a little more time in the field.

Animals↗
PubMed2003

A new member of the GM130 golgin subfamily is expressed in the optic lobe anlagen of the metamorphosing brain of Manduca sexta.

During metamorphosis of the insect brain, the optic lobe anlagen generate the proliferation centers for the visual cortices. We show here that, in the moth Manduca sexta, an 80 kDa Golgi complex protein (Ms-golgin80) is abundantly expressed in the cytoplasm of neuroblasts and ganglion mother cells in the optic lobe anlagen and proliferation centers. The predicted amino acid sequence for Ms-golgin80 is similar to that of several members of the GM130 subfamily of Golgi-associated proteins, including rat GM130 and human golgin-95. Homologs of Ms-golgin80 from Drosophila melanogaster, Caenorhabditis elegans, andBrugia malayi were identified through homology sequence search. Sequence similarities are present in three regions: the N-terminus, an internal domain of 89 amino acids, and another domain of 89 amino acids near the C-terminus. Structural similarities further suggest that these molecules play the same cellular role as GM130. GM130 is involved in the docking and fusion of coatomer (COP I) coated vesicles to the Golgi membranes; it also regulates the fragmentation and subsequent reassembly of the Golgi complex during mitosis. Abundant expression of Ms-golgin80 in neuroblasts and ganglion mother cells and its reduced expression in the neuronal progeny of these cells suggest that this protein may be involved in the maintenance of the proliferative state.

Amino Acid Sequence↗
PubMed2003

Patterns of PERIOD and pigment-dispersing hormone immunoreactivity in the brain of the European honeybee (Apis mellifera): age- and time-related plasticity.

We explored the neural basis of age- and task-related plasticity in circadian patterns of activity in the honeybee. To identify putative circadian pacemakers in the bee brain, we used antibodies against Drosophila melanogaster and Antheraea pernyi PERIOD and an antiserum to crustacean pigment-dispersing hormone (PDH) known to cross-react with insect pigment-dispersing factors (PDFs). In contrast to previous results from Drosophila, PDH and PER immunoreactivity (-ir) were not colocalized in bee neurons. The most intense PER-ir was cytoplasmic, in two groups of large neurons in the protocerebrum. The number of protocerebral PER-ir neurons and PER-ir intensity within individual cells were highest in brains collected during subjective night and higher in old bees than in young bees. These results are consistent with previous analyses of brain per mRNA in honeybees. Nuclear PER-ir was found throughout the brain, including the optic and antennal lobes. A single group of PDH-ir neurons (approximately 20/optic lobe) was consistently and intensely labeled at the medial margin of the medulla, independent of age or time of day. The processes of these neurons extended to specific neuropils in the protocerebrum and the optic lobes but not to the deutocerebrum. The patterns displayed by PER- and PDH-ir do not completely match any patterns previously described. This suggests that, although clock proteins are conserved across insect groups, there is no universal pattern of coexpression that allows ready identification of pacemaker neurons within the insect brain.

Aging↗
PubMed2003

Limits on volume changes in the mushroom bodies of the honey bee brain.

The behavioral maturation of adult worker honey bees is influenced by a rising titer of juvenile hormone (JH), and is temporally correlated with an increase in the volume of the neuropil of the mushroom bodies, a brain region involved in learning and memory. We explored the stability of this neuropil expansion and its possible dependence on JH. We studied the volume of the mushroom bodies in adult bees deprived of JH by surgical removal of the source glands, the corpora allata. We also asked if the neuropil expansion detected in foragers persists when bees no longer engage in foraging, either because of the onset of winter or because colony social structure was experimentally manipulated to cause some bees to revert from foraging to tending brood (nursing). Results show that adult exposure to JH is not necessary for growth of the mushroom body neuropil, and that the volume of the mushroom body neuropil in adult bees is not reduced if foraging stops. These results are interpreted in the context of a qualitative model that posits that mushroom body neuropil volume enlargement in the honey bee has both experience-independent and experience-dependent components.

Animals↗
PubMed2003

Juvenile hormone and division of labor in honey bee colonies: effects of allatectomy on flight behavior and metabolism.

Three experiments were performed to determine why removal of the corpora allata (the glands that produce juvenile hormone) causes honey bees to fail to return to their hive upon initiating flight. In Experiment 1, the naturally occurring flights of allatectomized bees were tracked with radar to determine whether the deficit is physical or cognitive. The results indicated a physical impairment: allatectomized bees had a significantly slower ground speed than sham and untreated bees during orientation flights, but otherwise attributes such as flight range and area were normal. Flight impairment was confirmed in Experiment 2, based on observations of takeoff made in the field at the hive entrance. The allatectomized group had a significantly smaller percentage of flightworthy bees than did the sham and untreated groups. Experiment 3 confirmed the flight impairment in laboratory tests and showed that allatectomy causes a decrease in metabolic rate. Allatectomized bees had significantly lower metabolic rates than untreated and sham bees, while allatectomized bees receiving hormone replacement had intermediate values. These results indicate that allatectomy causes flight impairment, probably partly due to effects on metabolic rate. They also suggest that juvenile hormone plays an additional, previously unknown, role in coordinating the physiological underpinning of division of labor in honey bee colonies.

Animals↗
PubMed2002

Integration of endocrine signals that regulate insect ecdysis.

The extremely large number of insects and members of allied groups alive today suggests that molting--shedding of an old cuticle--may be one of the most commonly performed behaviors on our planet. Removal of an old cuticle in insects is associated with stereotyped, species-specific patterns of behavior referred to as ecdysis. It has been recognized for decades that the initiation of ecdysis is under hormonal control, but until recently many of the key peptides that regulate ecdysis were unknown. The report in 1996 of a new ecdysis-triggering hormone (ETH) sparked an era of significant advances in our understanding of the regulation of molting. This article summarizes the current model of peptide regulation of ecdysis, a model that is based on a positive feedback loop between ETH and a brain peptide, eclosion hormone. Then the relationship of these regulatory peptides to the neural circuitry that is the ultimate driver of the behavior are described. Because insects can undergo both status quo (larval-larval) and metamorphic (larval-pupal and pupal-adult) molts, differences in ecdysis behavior at different life stages are described and potential sources of these differences are identified. Most of the work described is based on studies of ecdysis in the hawkmoth, Manduca sexta, but results from studies of ecdysis in the fruit fly Drosophila melanogaster are also discussed.

Animals↗