Variation in endocrine signaling is proposed to underlie the evolution and regulation of social l... more Variation in endocrine signaling is proposed to underlie the evolution and regulation of social life histories, but the genetic architecture of endocrine signaling is still poorly understood. An excellent example of a hormonally influenced set of social traits is found in the honey bee (Apis mellifera): a dynamic and mutually suppressive relationship between juvenile hormone (JH) and the yolk precursor protein vitellogenin (Vg) regulates behavioral maturation and foraging of workers. Several other traits cosegregate with these behavioral phenotypes, comprising the pollen hoarding syndrome (PHS) one of the best-described animal behavioral syndromes. Genotype differences in responsiveness of JH to Vg are a potential mechanistic basis for the PHS. Here, we reduced Vg expression via RNA interference in progeny from a backcross between 2 selected lines of honey bees that differ in JH responsiveness to Vg reduction and measured JH response and ovary size, which represents another key aspect of the PHS. Genetic mapping based on restriction site-associated DNA tag sequencing identified suggestive quantitative trait loci (QTL) for ovary size and JH responsiveness. We confirmed genetic effects on both traits near many QTL that had been identified previously for their effect on various PHS traits. Thus, our results support a role for endocrine control of complex traits at a genetic level. Furthermore, this first example of a genetic map of a hormonal response to gene knockdown in a social insect helps to refine the genetic understanding of complex behaviors and the physiology that may underlie behavioral control in general
We tested the influence of genetic variation on responses to natural and artificial diets in Varr... more We tested the influence of genetic variation on responses to natural and artificial diets in Varroa-resistant Pol-line and Russian honey bee stocks. Newly emerged workers from six colonies per stock were fed pollen, spirulina (blue-green microalgae), and sucrose-only diets in 144 total cages. Diet type had a strong effect on sugar intake, body weight, fat body lipid content, and vitellogenin (vg) expression. Spirulina consumption was approximately half that of pollen, but led to higher head weights, equivalent thorax weights and vg levels, and marginally reduced fat body lipids. Bee stock and colony had a significant impact on nutritional response. Despite equivalent diet intakes, Pol-line bees accumulated higher lipid levels and consumed less sugar overall than Russian bees. Furthermore, pollen-fed bees sourced from Pol-line colonies had significantly higher vg levels. These differences in nutrient and energy allocation may reflect life history-related physiological tradeoffs. Our ...
The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, ... more The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, yet its proximate underpinnings are elusive. Here, we used an artificial selection approach to create replicated lines of Japanese quail (Coturnix japonica) that differ genetically in their reproductive investment. Whole transcriptome sequencing revealed that females from lines selected for high reproductive output show a consistent upregulation of genes associated with reproduction but a simultaneous downregulation of immune genes. Concordant phenotypic differences in immune function (i.e., specific antibody response against keyhole limpet hemocyanin) were observed between the selection lines, even in males who do not provide parental care. Our findings demonstrate the key role of obligate transcriptional constraints in the maintenance of life history variation. These constraints set fundamental limits to productivity and health in natural and domestic animal populations.
Proceedings of the Royal Society B: Biological Sciences, 2017
Inbreeding depression refers to the reduction of fitness that results from matings between relati... more Inbreeding depression refers to the reduction of fitness that results from matings between relatives. Evidence for reduced fitness in inbred individuals is widespread, but the strength of inbreeding depression varies widely both within and among taxa. Environmental conditions can mediate this variation in the strength of inbreeding depression, with environmental stress exacerbating the negative consequences of inbreeding. Parents can modify the environment experienced by offspring, and have thus the potential to mitigate the negative consequences of inbreeding. While such parental effects have recently been demonstrated during the postnatal period, the role of prenatal parental effects in influencing the expression of inbreeding depression remains unexplored. To address this gap, we performed matings between full-sibs or unrelated individuals in replicated lines of Japanese quail ( Coturnix japonica ) experimentally selected for high and low maternal egg provisioning. We show that i...
In comparative gerontology, highly social insects such as honey bees (Apis mellifera) receive muc... more In comparative gerontology, highly social insects such as honey bees (Apis mellifera) receive much attention due to very different and flexible aging patterns among closely related siblings. While experimental strategies that manipulate socio-environmental factors suggest a causative link between aging and social signals and behaviors, the molecular underpinnings of this linkage are less well understood. Here we study the atypical localization of the egg-yolk protein vitellogenin (Vg) in the brain of the honey bee. Vg is known to influence honey bee social regulation and aging rate. Our findings suggest that Vg immunoreactivity in the brain is specifically localized within the class of non-neuronal glial cells. We discuss how these results can help explain the socially-dependent aging rate of honey bees.
The honeybee vitellogenin protein is receiving considerable attention in research that aims to un... more The honeybee vitellogenin protein is receiving considerable attention in research that aims to understand the regulatory causality and evolutionary history of social ontogeny, behavior, and life span. This chapter reviews the theoretical and experimental studies leading to the current insight that an endocrine-like action of vitellogenin can regulate major aspects of social organization.
Background: Meiotic recombination has traditionally been explained based on the structural requir... more Background: Meiotic recombination has traditionally been explained based on the structural requirement to stabilize homologous chromosome pairs to ensure their proper meiotic segregation. Competing hypotheses seek to explain the emerging findings of significant heterogeneity in recombination rates within and between genomes, but intraspecific comparisons of genome-wide recombination patterns are rare. The honey bee (Apis mellifera) exhibits the highest rate of genomic recombination among multicellular animals with about five cross-over events per chromatid. Results: Here, we present a comparative analysis of recombination rates across eight genetic linkage maps of the honey bee genome to investigate which genomic sequence features are correlated with recombination rate and with its variation across the eight data sets, ranging in average marker spacing ranging from 1 Mbp to 120 kbp. Overall, we found that GC content explained best the variation in local recombination rate along chromosomes at the analyzed 100 kbp scale. In contrast, variation among the different maps was correlated to the abundance of microsatellites and several specific tri-and tetra-nucleotides. Conclusions: The combined evidence from eight medium-scale recombination maps of the honey bee genome suggests that recombination rate variation in this highly recombining genome might be due to the DNA configuration instead of distinct sequence motifs. However, more fine-scale analyses are needed. The empirical basis of eight differing genetic maps allowed for robust conclusions about the correlates of the local recombination rates and enabled the study of the relation between DNA features and variability in local recombination rates, which is particularly relevant in the honey bee genome with its exceptionally high recombination rate.
Springer Proceedings in Mathematics & Statistics, 2014
Increasingly, studies demonstrate significant intra-specific variation in genome-wide recombinati... more Increasingly, studies demonstrate significant intra-specific variation in genome-wide recombination rates, supporting the notion that local rates of meiotic recombination are evolving. The honey bee, Apis mellifera, exhibits the highest rate of recombination across the genome among multicellular animals. Multiple linkage maps have been constructed and agree on the overall high recombination rate but local rates have not been compared in detail. Here, we compared eight genome-wide recombination maps at different scales to assess how they relate to each other. We found that variation from a 50 to 1,000 kbp scale does not systematically affect the moderate correlations among the recombination maps. Individual chromosomes differed from each other in how much recombination rates were conserved but no apparent relation to chromosome size or average recombination existed. Finally, the overall similarities among maps related more to methodological than to mapping population coalescence. Therefore, recombination maps that were constructed using different methods should be compared with caution and results that are derived from such multiple data sets should prove more robust than analyses of single maps, irrespective of intra-specific variation in recombination rates.
The rise in metabolic disorders in the past decades has heightened focus on achieving a healthy d... more The rise in metabolic disorders in the past decades has heightened focus on achieving a healthy dietary balance in humans. This is also an increasingly important issue in the management of honey bees (Apis mellifera) where poor nutrition has negative effects on health and productivity in agriculture, and nutrition is suggested as a contributing factor in the recent global declines in honey bee populations. As in other organisms, the insulin/insulin-like signaling (IIS) pathway is likely involved in maintaining nutrient homeostasis in honey bees. Honey bees have two insulin-like peptides (Ilps) with differing spatial expression patterns in the fat body suggesting that AmIlp1 potentially functions in lipid metabolism while AmIlp2 is a more general indicator of nutritional status. We fed caged worker bees artificial diets high in carbohydrates, proteins or lipids and measured expression of AmIlp1, AmIlp2, and the insulin receptor substrate (IRS) to test their responses to dietary macronutrients. We also measured lifespan, worker weight and gustatory sensitivity to sugar as measures of individual physical condition. We found that expression of AmIlp1 was affected by diet composition and was highest on a diet high in protein. Expression of AmIlp2 and AmIRS were not affected by diet. Workers lived longest on a diet high in carbohydrates and low in protein and lipids. However, bees fed this diet weighed less than those that received a diet high in protein and low in carbohydrates and lipids. Bees fed the high carbohydrates diet were also more responsive to sugar, potentially indicating greater levels of hunger. These results support a role for AmIlp1 in nutritional homeostasis and provide new insight into how unbalanced diets impact individual honey bee health.
Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely... more Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely tied to behavioral maturation. Workers who initiate foraging behavior at earlier ages have shorter lifespans, and much of the variation in total lifespan can be explained by differences in pre-foraging lifespan. Vitellogenin (Vg), a yolk precursor protein, influences worker lifespan both as a regulator of behavioral maturation and through anti-oxidant and immune functions. Experimental reduction of Vg mRNA, and thus Vg protein levels, in wild-type bees results in precocious foraging behavior, decreased lifespan, and increased susceptibility to oxidative damage. We sought to separate the effects of Vg on lifespan due to behavioral maturation from those due to immune and antioxidant function using two selected strains of honey bees that differ in their phenotypic responsiveness to Vg gene knockdown. Surprisingly, we found that lifespans lengthen in the strain described as behaviorally and...
Variation in endocrine signaling is proposed to underlie the evolution and regulation of social l... more Variation in endocrine signaling is proposed to underlie the evolution and regulation of social life histories, but the genetic architecture of endocrine signaling is still poorly understood. An excellent example of a hormonally influenced set of social traits is found in the honey bee (Apis mellifera): a dynamic and mutually suppressive relationship between juvenile hormone (JH) and the yolk precursor protein vitellogenin (Vg) regulates behavioral maturation and foraging of workers. Several other traits cosegregate with these behavioral phenotypes, comprising the pollen hoarding syndrome (PHS) one of the best-described animal behavioral syndromes. Genotype differences in responsiveness of JH to Vg are a potential mechanistic basis for the PHS. Here, we reduced Vg expression via RNA interference in progeny from a backcross between 2 selected lines of honey bees that differ in JH responsiveness to Vg reduction and measured JH response and ovary size, which represents another key aspe...
SUMMARY Nutrient sensitive insulin-like peptides (ILPs) have profound effects on invertebrate met... more SUMMARY Nutrient sensitive insulin-like peptides (ILPs) have profound effects on invertebrate metabolism, nutrient storage, fertility and aging. Many insects transcribe ILPs in specialized neurosecretory cells at changing levels correlated with life history. However, the major site of insect metabolism and nutrient storage is not the brain, but rather the fat body, where functions of ILP expression are rarely studied and poorly understood. Fat body is analogous to mammalian liver and adipose tissue, with nutrient stores that often correlate with behavior. We used the honey bee (Apis mellifera), an insect with complex behavior, to test whether ILP genes in fat body respond to experimentally induced changes of behavioral physiology. Honey bee fat body influences endocrine state and behavior by secreting the yolk protein precursor vitellogenin (Vg), which suppresses lipophilic juvenile hormone and social foraging behavior. In a two-factorial experiment, we used RNA interference (RNAi)-...
Summary In honey bees, Vitellogenin (Vg) is hypothesized to be a major factor affecting hormone s... more Summary In honey bees, Vitellogenin (Vg) is hypothesized to be a major factor affecting hormone signaling, food-related behavior, immunity, stress resistance and lifespan. Likewise microRNAs play important roles in posttranscriptional gene regulation and affect many biological processes. The action of microRNAs and Vg are known to intersect in the context of reproduction; however, the role of these associations on social behavior is unknown. The phenotypic effects of Vg knockdown are best established and studied in the forager stage of workers. Thus, we exploited the well-established RNA interference (RNAi) protocol for Vg knockdown to investigate its downstream effects on microRNA population in honey bee foragers' brain and fat body tissue. To identify microRNAs that are differentially expressed between tissues in control and knockdown foragers, we used µParaflo® microfluidic oligonucleotide microRNA microarrays. Our results show 76 and 74 microRNAs were expressed in the brain ...
Proceedings of the Royal Society B: Biological Sciences, 2011
Social castes of eusocial insects may have arisen through an evolutionary modification of an ance... more Social castes of eusocial insects may have arisen through an evolutionary modification of an ancestral reproductive ground plan, such that some adults emerge from development physiologically primed to specialize on reproduction (queens) and others on maternal care expressed as allo-maternal behaviour (workers). This hypothesis predicts that variation in reproductive physiology should emerge from ontogeny and underlie division of labour. To test these predictions, we identified physiological links to division of labour in a facultatively eusocial sweat bee,Megalopta genalis. Queens are larger, have larger ovaries and have higher vitellogenin titres than workers. We then compared queens and workers with their solitary counterparts—solitary reproductive females and dispersing nest foundresses—to investigate physiological variation as a factor in caste evolution. Within dyads, body size and ovary development were the best predictors of behavioural class. Queens and dispersers are larger...
Variation in endocrine signaling is proposed to underlie the evolution and regulation of social l... more Variation in endocrine signaling is proposed to underlie the evolution and regulation of social life histories, but the genetic architecture of endocrine signaling is still poorly understood. An excellent example of a hormonally influenced set of social traits is found in the honey bee (Apis mellifera): a dynamic and mutually suppressive relationship between juvenile hormone (JH) and the yolk precursor protein vitellogenin (Vg) regulates behavioral maturation and foraging of workers. Several other traits cosegregate with these behavioral phenotypes, comprising the pollen hoarding syndrome (PHS) one of the best-described animal behavioral syndromes. Genotype differences in responsiveness of JH to Vg are a potential mechanistic basis for the PHS. Here, we reduced Vg expression via RNA interference in progeny from a backcross between 2 selected lines of honey bees that differ in JH responsiveness to Vg reduction and measured JH response and ovary size, which represents another key aspect of the PHS. Genetic mapping based on restriction site-associated DNA tag sequencing identified suggestive quantitative trait loci (QTL) for ovary size and JH responsiveness. We confirmed genetic effects on both traits near many QTL that had been identified previously for their effect on various PHS traits. Thus, our results support a role for endocrine control of complex traits at a genetic level. Furthermore, this first example of a genetic map of a hormonal response to gene knockdown in a social insect helps to refine the genetic understanding of complex behaviors and the physiology that may underlie behavioral control in general
We tested the influence of genetic variation on responses to natural and artificial diets in Varr... more We tested the influence of genetic variation on responses to natural and artificial diets in Varroa-resistant Pol-line and Russian honey bee stocks. Newly emerged workers from six colonies per stock were fed pollen, spirulina (blue-green microalgae), and sucrose-only diets in 144 total cages. Diet type had a strong effect on sugar intake, body weight, fat body lipid content, and vitellogenin (vg) expression. Spirulina consumption was approximately half that of pollen, but led to higher head weights, equivalent thorax weights and vg levels, and marginally reduced fat body lipids. Bee stock and colony had a significant impact on nutritional response. Despite equivalent diet intakes, Pol-line bees accumulated higher lipid levels and consumed less sugar overall than Russian bees. Furthermore, pollen-fed bees sourced from Pol-line colonies had significantly higher vg levels. These differences in nutrient and energy allocation may reflect life history-related physiological tradeoffs. Our ...
The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, ... more The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, yet its proximate underpinnings are elusive. Here, we used an artificial selection approach to create replicated lines of Japanese quail (Coturnix japonica) that differ genetically in their reproductive investment. Whole transcriptome sequencing revealed that females from lines selected for high reproductive output show a consistent upregulation of genes associated with reproduction but a simultaneous downregulation of immune genes. Concordant phenotypic differences in immune function (i.e., specific antibody response against keyhole limpet hemocyanin) were observed between the selection lines, even in males who do not provide parental care. Our findings demonstrate the key role of obligate transcriptional constraints in the maintenance of life history variation. These constraints set fundamental limits to productivity and health in natural and domestic animal populations.
Proceedings of the Royal Society B: Biological Sciences, 2017
Inbreeding depression refers to the reduction of fitness that results from matings between relati... more Inbreeding depression refers to the reduction of fitness that results from matings between relatives. Evidence for reduced fitness in inbred individuals is widespread, but the strength of inbreeding depression varies widely both within and among taxa. Environmental conditions can mediate this variation in the strength of inbreeding depression, with environmental stress exacerbating the negative consequences of inbreeding. Parents can modify the environment experienced by offspring, and have thus the potential to mitigate the negative consequences of inbreeding. While such parental effects have recently been demonstrated during the postnatal period, the role of prenatal parental effects in influencing the expression of inbreeding depression remains unexplored. To address this gap, we performed matings between full-sibs or unrelated individuals in replicated lines of Japanese quail ( Coturnix japonica ) experimentally selected for high and low maternal egg provisioning. We show that i...
In comparative gerontology, highly social insects such as honey bees (Apis mellifera) receive muc... more In comparative gerontology, highly social insects such as honey bees (Apis mellifera) receive much attention due to very different and flexible aging patterns among closely related siblings. While experimental strategies that manipulate socio-environmental factors suggest a causative link between aging and social signals and behaviors, the molecular underpinnings of this linkage are less well understood. Here we study the atypical localization of the egg-yolk protein vitellogenin (Vg) in the brain of the honey bee. Vg is known to influence honey bee social regulation and aging rate. Our findings suggest that Vg immunoreactivity in the brain is specifically localized within the class of non-neuronal glial cells. We discuss how these results can help explain the socially-dependent aging rate of honey bees.
The honeybee vitellogenin protein is receiving considerable attention in research that aims to un... more The honeybee vitellogenin protein is receiving considerable attention in research that aims to understand the regulatory causality and evolutionary history of social ontogeny, behavior, and life span. This chapter reviews the theoretical and experimental studies leading to the current insight that an endocrine-like action of vitellogenin can regulate major aspects of social organization.
Background: Meiotic recombination has traditionally been explained based on the structural requir... more Background: Meiotic recombination has traditionally been explained based on the structural requirement to stabilize homologous chromosome pairs to ensure their proper meiotic segregation. Competing hypotheses seek to explain the emerging findings of significant heterogeneity in recombination rates within and between genomes, but intraspecific comparisons of genome-wide recombination patterns are rare. The honey bee (Apis mellifera) exhibits the highest rate of genomic recombination among multicellular animals with about five cross-over events per chromatid. Results: Here, we present a comparative analysis of recombination rates across eight genetic linkage maps of the honey bee genome to investigate which genomic sequence features are correlated with recombination rate and with its variation across the eight data sets, ranging in average marker spacing ranging from 1 Mbp to 120 kbp. Overall, we found that GC content explained best the variation in local recombination rate along chromosomes at the analyzed 100 kbp scale. In contrast, variation among the different maps was correlated to the abundance of microsatellites and several specific tri-and tetra-nucleotides. Conclusions: The combined evidence from eight medium-scale recombination maps of the honey bee genome suggests that recombination rate variation in this highly recombining genome might be due to the DNA configuration instead of distinct sequence motifs. However, more fine-scale analyses are needed. The empirical basis of eight differing genetic maps allowed for robust conclusions about the correlates of the local recombination rates and enabled the study of the relation between DNA features and variability in local recombination rates, which is particularly relevant in the honey bee genome with its exceptionally high recombination rate.
Springer Proceedings in Mathematics & Statistics, 2014
Increasingly, studies demonstrate significant intra-specific variation in genome-wide recombinati... more Increasingly, studies demonstrate significant intra-specific variation in genome-wide recombination rates, supporting the notion that local rates of meiotic recombination are evolving. The honey bee, Apis mellifera, exhibits the highest rate of recombination across the genome among multicellular animals. Multiple linkage maps have been constructed and agree on the overall high recombination rate but local rates have not been compared in detail. Here, we compared eight genome-wide recombination maps at different scales to assess how they relate to each other. We found that variation from a 50 to 1,000 kbp scale does not systematically affect the moderate correlations among the recombination maps. Individual chromosomes differed from each other in how much recombination rates were conserved but no apparent relation to chromosome size or average recombination existed. Finally, the overall similarities among maps related more to methodological than to mapping population coalescence. Therefore, recombination maps that were constructed using different methods should be compared with caution and results that are derived from such multiple data sets should prove more robust than analyses of single maps, irrespective of intra-specific variation in recombination rates.
The rise in metabolic disorders in the past decades has heightened focus on achieving a healthy d... more The rise in metabolic disorders in the past decades has heightened focus on achieving a healthy dietary balance in humans. This is also an increasingly important issue in the management of honey bees (Apis mellifera) where poor nutrition has negative effects on health and productivity in agriculture, and nutrition is suggested as a contributing factor in the recent global declines in honey bee populations. As in other organisms, the insulin/insulin-like signaling (IIS) pathway is likely involved in maintaining nutrient homeostasis in honey bees. Honey bees have two insulin-like peptides (Ilps) with differing spatial expression patterns in the fat body suggesting that AmIlp1 potentially functions in lipid metabolism while AmIlp2 is a more general indicator of nutritional status. We fed caged worker bees artificial diets high in carbohydrates, proteins or lipids and measured expression of AmIlp1, AmIlp2, and the insulin receptor substrate (IRS) to test their responses to dietary macronutrients. We also measured lifespan, worker weight and gustatory sensitivity to sugar as measures of individual physical condition. We found that expression of AmIlp1 was affected by diet composition and was highest on a diet high in protein. Expression of AmIlp2 and AmIRS were not affected by diet. Workers lived longest on a diet high in carbohydrates and low in protein and lipids. However, bees fed this diet weighed less than those that received a diet high in protein and low in carbohydrates and lipids. Bees fed the high carbohydrates diet were also more responsive to sugar, potentially indicating greater levels of hunger. These results support a role for AmIlp1 in nutritional homeostasis and provide new insight into how unbalanced diets impact individual honey bee health.
Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely... more Honey bee workers display remarkable flexibility in the aging process. This plasticity is closely tied to behavioral maturation. Workers who initiate foraging behavior at earlier ages have shorter lifespans, and much of the variation in total lifespan can be explained by differences in pre-foraging lifespan. Vitellogenin (Vg), a yolk precursor protein, influences worker lifespan both as a regulator of behavioral maturation and through anti-oxidant and immune functions. Experimental reduction of Vg mRNA, and thus Vg protein levels, in wild-type bees results in precocious foraging behavior, decreased lifespan, and increased susceptibility to oxidative damage. We sought to separate the effects of Vg on lifespan due to behavioral maturation from those due to immune and antioxidant function using two selected strains of honey bees that differ in their phenotypic responsiveness to Vg gene knockdown. Surprisingly, we found that lifespans lengthen in the strain described as behaviorally and...
Variation in endocrine signaling is proposed to underlie the evolution and regulation of social l... more Variation in endocrine signaling is proposed to underlie the evolution and regulation of social life histories, but the genetic architecture of endocrine signaling is still poorly understood. An excellent example of a hormonally influenced set of social traits is found in the honey bee (Apis mellifera): a dynamic and mutually suppressive relationship between juvenile hormone (JH) and the yolk precursor protein vitellogenin (Vg) regulates behavioral maturation and foraging of workers. Several other traits cosegregate with these behavioral phenotypes, comprising the pollen hoarding syndrome (PHS) one of the best-described animal behavioral syndromes. Genotype differences in responsiveness of JH to Vg are a potential mechanistic basis for the PHS. Here, we reduced Vg expression via RNA interference in progeny from a backcross between 2 selected lines of honey bees that differ in JH responsiveness to Vg reduction and measured JH response and ovary size, which represents another key aspe...
SUMMARY Nutrient sensitive insulin-like peptides (ILPs) have profound effects on invertebrate met... more SUMMARY Nutrient sensitive insulin-like peptides (ILPs) have profound effects on invertebrate metabolism, nutrient storage, fertility and aging. Many insects transcribe ILPs in specialized neurosecretory cells at changing levels correlated with life history. However, the major site of insect metabolism and nutrient storage is not the brain, but rather the fat body, where functions of ILP expression are rarely studied and poorly understood. Fat body is analogous to mammalian liver and adipose tissue, with nutrient stores that often correlate with behavior. We used the honey bee (Apis mellifera), an insect with complex behavior, to test whether ILP genes in fat body respond to experimentally induced changes of behavioral physiology. Honey bee fat body influences endocrine state and behavior by secreting the yolk protein precursor vitellogenin (Vg), which suppresses lipophilic juvenile hormone and social foraging behavior. In a two-factorial experiment, we used RNA interference (RNAi)-...
Summary In honey bees, Vitellogenin (Vg) is hypothesized to be a major factor affecting hormone s... more Summary In honey bees, Vitellogenin (Vg) is hypothesized to be a major factor affecting hormone signaling, food-related behavior, immunity, stress resistance and lifespan. Likewise microRNAs play important roles in posttranscriptional gene regulation and affect many biological processes. The action of microRNAs and Vg are known to intersect in the context of reproduction; however, the role of these associations on social behavior is unknown. The phenotypic effects of Vg knockdown are best established and studied in the forager stage of workers. Thus, we exploited the well-established RNA interference (RNAi) protocol for Vg knockdown to investigate its downstream effects on microRNA population in honey bee foragers' brain and fat body tissue. To identify microRNAs that are differentially expressed between tissues in control and knockdown foragers, we used µParaflo® microfluidic oligonucleotide microRNA microarrays. Our results show 76 and 74 microRNAs were expressed in the brain ...
Proceedings of the Royal Society B: Biological Sciences, 2011
Social castes of eusocial insects may have arisen through an evolutionary modification of an ance... more Social castes of eusocial insects may have arisen through an evolutionary modification of an ancestral reproductive ground plan, such that some adults emerge from development physiologically primed to specialize on reproduction (queens) and others on maternal care expressed as allo-maternal behaviour (workers). This hypothesis predicts that variation in reproductive physiology should emerge from ontogeny and underlie division of labour. To test these predictions, we identified physiological links to division of labour in a facultatively eusocial sweat bee,Megalopta genalis. Queens are larger, have larger ovaries and have higher vitellogenin titres than workers. We then compared queens and workers with their solitary counterparts—solitary reproductive females and dispersing nest foundresses—to investigate physiological variation as a factor in caste evolution. Within dyads, body size and ovary development were the best predictors of behavioural class. Queens and dispersers are larger...
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Papers by Kate Ihle