Differential expression of mitochondrial genes between queens and workers during caste determination in the honeybee Apis mellifera.
The nourishment received by female honeybee larvae determines their differentiation into queens or workers. In this study, we report the first molecular analysis of differences that occur between queens and workers during the caste-determination process. RNA-differential display experiments identified a clone that encodes for a gene that is homologous to the nuclear-encoded mitochondrial translation initiation factor (AmIF-2mt). Semi-quantitative analysis by reverse transcriptase/polymerase chain reaction (RT-PCR) throughout honeybee development detected a higher level of expression of this gene in queen larvae than in worker larvae. Analysis of two other genes encoding mitochondrial proteins, cytochrome oxidase subunit 1 (COX-1; mitochondrial-encoded) and cytochrome c (cyt c; nuclear-encoded) also showed differential expression of these two genes between queens and workers. In particular, the cyt c transcript is more abundant in queen larvae and throughout the metamorphosis of the queen. These results indicate that the higher respiratory rate previously documented in queen larvae is accomplished through a higher level of expression of both nuclear- and mitochondrial-encoded genes for mitochondrial proteins. (+info)
IA in Kenyon cells of the mushroom body of honeybees resembles shaker currents: kinetics, modulation by K+, and simulation.
Cultured Kenyon cells from the mushroom body of the honeybee, Apis mellifera, show a voltage-gated, fast transient K+ current that is sensitive to 4-aminopyridine, an A current. The kinetic properties of this A current and its modulation by extracellular K+ ions were investigated in vitro with the whole cell patch-clamp technique. The A current was isolated from other voltage-gated currents either pharmacologically or with suitable voltage-clamp protocols. Hodgkin- and Huxley-style mathematical equations were used for the description of this current and for the simulation of action potentials in a Kenyon cell model. Activation and inactivation of the A current are fast and voltage dependent with time constants of 0.4 +/- 0.1 ms (means +/- SE) at +45 mV and 3.0 +/- 1.6 ms at +45 mV, respectively. The pronounced voltage dependence of the inactivation kinetics indicates that at least a part of this current of the honeybee Kenyon cells is a shaker-like current. Deactivation and recovery from inactivation also show voltage dependency. The time constant of deactivation has a value of 0.4 +/- 0.1 ms at -75 mV. Recovery from inactivation needs a double-exponential function to be fitted adequately; the resulting time constants are 18 +/- 3.1 ms for the fast and 745 +/- 107 ms for the slow process at -75 mV. Half-maximal activation of the A current occurs at -0.7 +/- 2.9 mV, and half-maximal inactivation occurs at -54.7 +/- 2.4 mV. An increase in the extracellular K+ concentration increases the conductance and accelerates the recovery from inactivation of the A current, affecting the slow but not the fast time constant. With respect to these modulations the current under investigation resembles some of the shaker-like currents. The data of the A current were incorporated into a reduced computational model of the voltage-gated currents of Kenyon cells. In addition, the model contained a delayed rectifier K+ current, a Na+ current, and a leakage current. The model is able to generate an action potential on current injection. The model predicts that the A current causes repolarization of the action potential but not a delay in the initiation of the action potential. It further predicts that the activation of the delayed rectifier K+ current is too slow to contribute markedly to repolarization during a single action potential. Because of its fast activation, the A current reduces the amplitude of the net depolarizing current and thus reduces the peak amplitude and the duration of the action potential. (+info)
Biological activities of C-terminal 15-residue synthetic fragment of melittin: design of an analog with improved antibacterial activity.
Melittin, the 26-residue predominant toxic peptide from bee venom, exhibits potent antibacterial activity in addition to its hemolytic activity. The synthetic peptide of 15 residues corresponding to its C-terminal end (MCF), which encompasses its most amphiphilic segment, is now being shown to possess antibacterial activity about 5-7 times less compared to that of melittin. MCF, however, is 300 times less hemolytic. An analog of MCF, MCFA, in which two cationic residues have been transpositioned to the N-terminal region from the C-terminal region, exhibits antibacterial activity comparable to that of melittin, but is only marginally more hemolytic than MCF. The biophysical properties of the peptides, like folding and aggregation, correlate well with their biological properties. (+info)
A PCR detection method for rapid identification of Paenibacillus larvae.
American foulbrood is a disease of larval honeybees (Apis mellifera) caused by the bacterium Paenibacillus larvae. Over the years attempts have been made to develop a selective medium for the detection of P. larvae spores from honey samples. The most successful of these is a semiselective medium containing nalidixic acid and pipermedic acid. Although this medium allows the growth of P. larvae and prevents the growth of most other bacterial species, the false-positive colonies that grow on it prevent the rapid confirmation of the presence of P. larvae. Here we describe a PCR detection method which can be used on the colonies that grow on this semiselective medium and thereby allows the rapid confirmation of the presence of P. larvae. The PCR primers were designed on the basis of the 16S rRNA gene of P. larvae and selectively amplify a 973-bp amplicon. The PCR amplicon was confirmed as originating from P. larvae by sequencing in both directions. Detection was specific for P. larvae, and the primers did not hybridize with DNA from closely related bacterial species. (+info)
Differential gene expression between developing queens and workers in the honey bee, Apis mellifera.
Many insects show polyphenisms, or alternative morphologies, which are based on differential gene expression rather than genetic polymorphism. Queens and workers are alternative forms of the adult female honey bee and represent one of the best known examples of insect polyphenism. Hormonal regulation of caste determination in honey bees has been studied in detail, but little is known about the proximate molecular mechanisms underlying this process, or any other such polyphenism. We report the success of a molecular-genetic approach for studying queen- and worker-specific gene expression in the development of the honey bee (Apis mellifera). Numerous genes appear to be differentially expressed between the two castes. Seven differentially expressed loci described here belong to at least five distinctly different evolutionary and functional groups. Two are particularly promising as potential regulators of caste differentiation. One is homologous to a widespread class of proteins that bind lipids and other hydrophobic ligands, including retinoic acid. The second locus shows sequence similarity to a DNA-binding domain in the Ets family of transcription factors. The remaining loci appear to be involved with downstream changes inherent to queen- or worker-specific developmental pathways. Caste determination in honey bees is typically thought of as primarily queen determination; our results make it clear that the process involves specific activation of genes in workers as well as in queens. (+info)
The role of orientation flights on homing performance in honeybees.
Honeybees have long served as a model organism for investigating insect navigation. Bees, like many other nesting animals, primarily use learned visual features of the environment to guide their movement between the nest and foraging sites. Although much is known about the spatial information encoded in memory by experienced bees, the development of large-scale spatial memory in naive bees is not clearly understood. Past studies suggest that learning occurs during orientation flights taken before the start of foraging. We investigated what honeybees learn during their initial experience in a new landscape by examining the homing of bees displaced after a single orientation flight lasting only 5-10 min. Homing ability was assessed using vanishing bearings and homing speed. At release sites with a view of the landmarks immediately surrounding the hive, 'first-flight' bees, tested after their very first orientation flight, had faster homing rates than 'reorienting foragers', which had previous experience in a different site prior to their orientation flight in the test landscape. First-flight bees also had faster homing rates from these sites than did 'resident' bees with full experience of the terrain. At distant sites, resident bees returned to the hive more rapidly than reorienting or first-flight bees; however, in some cases, the reorienting bees were as successful as the resident bees. Vanishing bearings indicated that all three types of bees were oriented homewards when in the vicinity of landmarks near the hive. When bees were released out of sight of these landmarks, hence forcing them to rely on a route memory, the 'first-flight' bees were confused, the 'reorienting' bees chose the homeward direction except at the most distant site and the 'resident' bees were consistently oriented homewards. (+info)
Update on the status of Africanized honey bees in the western states.
The Africanized honey bee (AHB), Apis mellifera scutella--perhaps better known as the "killer bee"--has arrived in the western United States and in southern California, following a nearly 50-year north-ward migration across South and Central America. First detected near Hidalgo, Texas in October 1993, the bees continue to advance 100 to 300 miles per year by colonizing existing hives or forming new hives in the wild. Although the AHB's "killer" reputation has been greatly exaggerated, the presence of AHBs will increase the chances of people being stung. (+info)
Mass envenomations by honey bees and wasps.
Stinging events involving honey bees and wasps are rare; most deaths or clinically important incidents involve very few stings (< 10) and anaphylactic shock. However, mass stinging events can prove life-threatening via the toxic action of the venom when injected in large amounts. With the advent of the Africanized honey bee in the southwestern United States and its potential for further spread, mass envenomation incidents will increase. Here we review the literature on mass stinging events involving honey bees and wasps (i.e., yellowjackets, wasps, and hornets). Despite different venom composition in the two insect groups, both may cause systemic damage and involve hemolysis, rhabdomyolysis, and acute renal failure. Victim death may occur due to renal failure or cardiac complications. With supportive care, however, most victims should be able to survive attacks from hundreds of wasps or approximately 1000 honey bees. (+info)