Miguel E. Arechavaleta-Velasco

Behavioral genomics of honeybee foraging and nest defense

The honeybee has been the most important insect species for study of social behavior. The recently released draft genomic sequence for the bee will accelerate honeybee behavioral genetics. Although we lack sufficient tools to manipulate this genome easily, quantitative trait loci (QTLs) that influence natural variation in behavior have been identified and tested for their effects on correlated behavioral traits. We review what is known about the genetics and physiology of two behavioral traits in honeybees, foraging specialization (pollen versus nectar), and defensive behavior, and present evidence that map-based cloning of genes is more feasible in the bee than in other metazoans. We also present bioinformatic analyses of candidate genes within QTL confidence intervals (CIs). The high recombination rate of the bee made it possible to narrow the search to regions containing only 17–61 predicted peptides for each QTL, although CIs covered large genetic distances. Knowledge of correlated behavioral traits, comparative bioinformatics, and expression assays facilitated evaluation of candidate genes. An overrepresentation of genes involved in ovarian development and insulin-like signaling components within pollen foraging QTL regions suggests that an ancestral reproductive gene network was co-opted during the evolution of foraging specialization. The major QTL influencing defensive/aggressive behavior contains orthologs of genes involved in central nervous system activity and neurogenesis. Candidates at the other two defensive-behavior QTLs include modulators of sensory signaling (Am5HT7 serotonin receptor, AmArr4 arrestin, and GABA-B-R1 receptor). These studies are the first step in linking natural variation in honeybee social behavior to the identification of underlying genes.

Confirmation of QTL Effects and Evidence of Genetic Dominance of Honeybee Defensive Behavior: Results of Colony and Individual Behavioral Assays

The stinging and guarding components of the defensive behavior of European, Africanized, hybrid, and backcross honeybees (Apis mellifera L.) were compared and analyzed at both colony and individual levels. Hybrid and Africanized backcross colonies stung as many times as Africanized ones. European backcross colonies stung more than European bees but not as many times as Africanized or Africanized backcross colonies. The degree of dominance for the number of times that worker bees stung a leather patch was estimated to be 84.3%, 200.8%, and 145.8% for hybrid, backcross European, and backcross Africanized colonies, respectively. Additionally, both guards at the colony entrance and fast-stinging workers of one European backcross colony had a significantly higher frequency of an Africanized DNA marker allele, located near “sting1,” a QTL previously implicated in stinging behavior at the colony level. However, guards and fast-stinging bees from a backcross to the Africanized parental colony did not differ from control bees in their frequency for the Africanized and European markers, as would be expected if large genetic dominance effects for sting1 exist. These results support the hypothesis that genetic dominance influences the defensive behavior of honeybees and confirm the effect of sting1 on the defensiveness of individual worker bees.

Quantitative Trait Loci That Influence the Expression of Guarding and Stinging Behaviors of Individual Honey Bees

This study was conducted to test for the effect of three stinging behaviors QTLs (sting-1, sting-2 and sting-3) on the expression of guarding and stinging behavior of individual honey bees, and to determine if results of defensive behavior QTLs found in studies with Africanized honey bees could be extended to other populations of bees. Samples of guards, stingers, foragers and nurse bees were taken from two backcross colonies derived from a defensive colony and a gentle colony. The genotype of each bee for both types of colonies was determined for two sequence tagged site (STS) markers linked to sting-1 and for another two STSs, one linked to sting-2 and one linked to sting-3. Results showed that sting-1 had an effect on the expression of both stinging and guarding behaviors, sting-2 and sting-3 influenced the expression of guarding behavior. These results indicate that division of labor is influenced by specific QTLs. Results also show that QTLs mapped in a population of Africanized honey bees using colony level phenotypes also influenced the expression of guarding and stinging behavior of individual bees of other populations.

Fine-scale linkage mapping reveals a small set of candidate genes influencing honey bee grooming behavior in response to Varroa mites.

Populations of honey bees in North America have been experiencing high annual colony mortality for 15–20 years. Many apicultural researchers believe that introduced parasites called Varroa mites (V. destructor) are the most important factor in colony deaths. One important resistance mechanism that limits mite population growth in colonies is the ability of some lines of honey bees to groom mites from their bodies. To search for genes influencing this trait, we used an Illumina Bead Station genotyping array to determine the genotypes of several hundred worker bees at over a thousand single-nucleotide polymorphisms in a family that was apparently segregating for alleles influencing this behavior. Linkage analyses provided a genetic map with 1,313 markers anchored to genome sequence. Genotypes were analyzed for association with grooming behavior, measured as the time that individual bees took to initiate grooming after mites were placed on their thoraces. Quantitative-trait-locus interval mapping identified a single chromosomal region that was significant at the chromosome-wide level (p<0.05) on chromosome 5 with a LOD score of 2.72. The 95% confidence interval for quantitative trait locus location contained only 27 genes (honey bee official gene annotation set 2) including Atlastin, Ataxin and Neurexin-1 (AmNrx1), which have potential neurodevelopmental and behavioral effects. Atlastin and Ataxin homologs are associated with neurological diseases in humans. AmNrx1 codes for a presynaptic protein with many alternatively spliced isoforms. Neurexin-1 influences the growth, maintenance and maturation of synapses in the brain, as well as the type of receptors most prominent within synapses. Neurexin-1 has also been associated with autism spectrum disorder and schizophrenia in humans, and self-grooming behavior in mice.

Binary Trait Loci That Influence Honey Bee (Hymenoptera: Apidae) Guarding Behavior

Abstract This study was conducted to detect binary trait loci (BTLs) that influence guarding behavior of individual honey bees, Apis mellifera L., and to locate genetic markers that are associated with these BTLs on genetic maps derived from guard bees from two reciprocal backcross colonies. Samples of guards and control bees were taken from two backcross colonies derived from a defensive colony and a gentle colony. Amplified fragment length polymorphism (AFLP) markers were produced from DNA samples of guards. Two genetic maps were generated, one for each type of colony. A chi-square goodness-of-fit test was performed for each marker in the map to look for deviations from the 1:1 segregation of the markers. For those markers that significantly deviated from the 1:1 ratio in the guards, AFLPs were generated from two samples of control bees, one for each type of backcross. Those markers that showed a skewed segregation pattern in the guards but not in the controls were analyzed with a 2 × 2 chi-square to test for associations between the markers and the expression of the trait. Ten markers were associated with guarding behavior (five in each backcross). The 10 markers represented seven putative BTLs that influence honey bee guarding behavior. One of the BTLs represents a QTL that was previously detected in analysis of colony-level stinging response, others represent new loci specific to the behavior of individuals guarding the colony entrance.

A search for parent-of-origin effects on honey bee gene expression

Parent-specific gene expression (PSGE) is little known outside of mammals and plants. PSGE occurs when the expression level of a gene depends on whether an allele was inherited from the mother or the father. Kin selection theory predicts that there should be extensive PSGE in social insects because social insect parents can gain inclusive fitness benefits by silencing parental alleles in female offspring. We searched for evidence of PSGE in honey bees using transcriptomes from reciprocal crosses between European and Africanized strains. We found 46 transcripts with significant parent-of-origin effects on gene expression, many of which overexpressed the maternal allele. Interestingly, we also found a large proportion of genes showing a bias toward maternal alleles in only one of the reciprocal crosses. These results indicate that PSGE may occur in social insects. The nonreciprocal effects could be largely driven by hybrid incompatibility between these strains. Future work will help to determine if these are indeed parent-of-origin effects that can modulate inclusive fitness benefits.

Nosema ceranae has parasitized Africanized honey bees in Mexico since at least 2004

Ernesto Guzman-Novoa, Mollah Md Hamiduzzaman, Miguel E Arechavaleta-Velasco, Gun Koleoglu, Pegah Valizadeh and Adriana Correa-Benitez School of Environmental Sciences, University of Guelph, 50 Stone Road East, Guelph, Ontario, N1G 2W1, Canada. Centro Nacional de Investigacion en Fisiologia y Mejoramiento Animal, INIFAP, km 1 Carretera a Colon, Ajuchitlan, Qro. Mexico. Departamento de Produccion Animal: Abejas, FMVZ, UNAM, Cd. Univ., Mexico DF 04510, Mexico.

Biased Allele Expression and Aggression in Hybrid Honeybees may be Influenced by Inappropriate Nuclear-Cytoplasmic Signaling

Hybrid effects are often exhibited asymmetrically between reciprocal families. One way this could happen is if silencing of one parent’s allele occurs in one lineage but not the other, which could affect the phenotypes of the hybrids asymmetrically by silencing that allele in only one of the hybrid families. We have previously tested for allele-specific expression biases in hybrids of European and Africanized honeybees and we found that there was an asymmetric overabundance of genes showing a maternal bias in the family with a European mother. Here, we further analyze allelic bias in these hybrids to ascertain whether they may underlie previously described asymmetries in metabolism and aggression in similar hybrid families and we speculate on what mechanisms may produce this biased allele usage. We find that there are over 500 genes that have some form of biased allele usage and over 200 of these are biased toward the maternal allele but only in the family with European maternity, mirroring the pattern observed for aggression and metabolic rate. This asymmetrically biased set is enriched for genes in loci associated with aggressive behavior and also for mitochondrial-localizing proteins. It contains many genes that play important roles in metabolic regulation. Moreover we find genes relating to the piwi-interacting RNA (piRNA) pathway, which is involved in chromatin modifications and epigenetic regulation and may help explain the mechanism underlying this asymmetric allele use. Based on these findings and previous work investigating aggression and metabolism in bees, we propose a novel hypothesis; that the asymmetric pattern of biased allele usage in these hybrids is a result of inappropriate use of piRNA-mediated nuclear-cytoplasmic signaling that is normally used to modulate aggression in honeybees. This is the first report of widespread asymmetric effects on allelic expression in hybrids and may represent a novel mechanism for gene regulation.

Evaluation of metabolic, endrocrine and growth features in the Mexican hairless pig to determinate its potential as model for obesity in comparison with commercial pigs

Biochemical, endocrine and growth performance variables were evaluated and compared in the Mexican hairless (MHP) and in Landrace Yorkshires pigs (LYP) from first to ninth month of age in order to establish if the MHP could be a better model for the study of obesity than the LYP. Serum concentrations of total cholesterol (TC), triglycerides (TG), high-density lipoproteins (HDL), low-density lipoproteins (LDL), glucose, free fatty acids (FFA), and insulin were measured. Feed intake, body weight and backfat thickness were also monitored. The results showed that the MHP partitioned more energy to backfat than the LYP (P<0.01), and had higher fasting serum concentrations of insulin, TC, TG, LDL, and FFA than the LYP (P<0.05). Based on the high capacity of the MHP to deposit body fat, and its higher serum concentrations of insulin, TG, CT, LDL, and FFA, we conclude that the MHP is a better model for the study of obesity than the Landrace-Yorkshire pigs and could be used under experimental conditions as a model for obesity, particularly the observed in metabolically healthy but obese humans.

Prevalencia de la acariosis traqueal y niveles de infestación de Acarapis woodi en colonias de abejas de Morelos, México

Tracheal mite disease caused by Acarapis woodi is one of the most important diseases that affect honeybees. The objective of this study was to estimate the prevalence of tracheal mite disease and the levels of infestation of A.woodi in honeybee colonies in the State of Morelos, where beekeeping is an important activity performed in different climate conditions and under different production systems. This study was conducted using 1,198 honeybee colonies, located in 233 apiaries distributed along the state. The colonies belong to 96 beekeeping productive units. The apiaries included in the study represent 21.5 % of the apiaries in the State and the beekeeping productive units represent the 13.7 % of the beekeeping units registered in Morelos. The results of the study indicate that the prevalence of the tracheal mite disease in Morelos is 0.02 and that 10.30 % of the apiaries included in the study had at least one colony infected with the disease. The average percent infestation in the positive colonies was 7.32 ± 0.75, with a minimum level of infestation of 5 % and a maximum level of 20 %. These results indicate that currently the prevalence of the tracheal mite disease in Morelos is relatively low and that the average level of infestation estimated is low; the results indicate also that the prevalence estimated in this study for this disease is lower than the reported 34 yr ago.