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PNAS 104 (7): 2460-2464

Copyright © 2007 by the National Academy of Sciences.

Queen pheromone modulates brain dopamine function in worker honey bees

Kyle T. Beggs*, Kelly A. Glendining*, Nicola M. Marechal*, Vanina Vergoz*, Ikumi Nakamura*, Keith N. Slessor{dagger},{ddagger}, and Alison R. Mercer*,§

*Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand; and {dagger}Department of Chemistry, Simon Fraser University, Burnaby, BC, Canada V5A 1S6


Figure 1
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Fig. 1. Honey bee queen surrounded by a retinue of workers attracted to her by QMP. The schematics show that one component of QMP, HVA, bears a striking structural resemblance to dopamine.

 

Figure 2
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Fig. 2. Brain dopamine (DA) levels in 2-day-old worker bees. (A) QMP exposure reduces levels of dopamine in the brain. (B) Young hive bees exposed to a mated queen show lower brain dopamine levels than those exposed to a virgin queen. (C) Reduction of brain dopamine levels after exposure to HVA. (D) Brain dopamine levels are not affected by exposure to HOB. (E) Reduction of brain dopamine levels from exposure to HVA and HOB combined. Data are expressed as means ± SEM. Numbers in each bar represent n values. P values show the significance of differences between groups as determined by two-tailed Student's t tests.

 

Figure 3
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Fig. 3. Age-related changes in dopamine receptor gene mRNA levels quantified by Northern blot analysis. Comparison of transcript levels in the brains of newly emerged adults (NE), 1-day-old workers (1 day), 2-day-old workers (2 day), and foragers (For; generally >21 days old) reveals age-related changes in the expression of Amdop1 (A), Amdop2 (B), and Amdop3 (C). Data are expressed as means ± SEM with a sample size of four independent RNA samples for each group. Overall significance was determined by one-way ANOVA with Tukey's tests used for post hoc comparisons. Letters above the bars indicate differences between groups. Groups that share letters are not significantly different.

 

Figure 4
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Fig. 4. QMP modulation of dopamine receptor gene expression. (A–C) Northern blot analysis of gene transcript levels in 2-day-old workers. (A) Amdop1 mRNA levels are significantly lower in 2-day-old QMP-treated bees than in age-matched controls. (B and C) No significant differences in Amdop2 (B) or Amdop3 (C) mRNA levels were identified among QMP-treated bees and controls. (D–F) Gene expression levels determined by using quantitative RT-PCR. (D) Amdop1 transcript levels are selectively reduced by exposure to QMP. (E and F) Differences in Amdop2 (E) and Amdop3 (F) mRNA levels between QMP-treated bees and controls are not significant. Data are expressed as mean levels ± SEM with a sample size of three for each group. Statistical comparisons were performed by using two-tailed Student's t tests.

 

Figure 5
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Fig. 5. Responses of isolated mushroom body calyces to dopamine monitored by using measurements of intracellular cAMP. Calyces from QMP-exposed bees (gray bars) and from control bees (white bars) were exposed to either 10 µM dopamine (A) or 10 µM HVA (B). Note that dopamine-evoked responses are strikingly different in QMP-treated bees versus controls and that the effects of dopamine are mimicked by HVA. Data are expressed as mean levels ± SEM with a sample size of six for each group. P values refer to within-group differences between cAMP levels detected in dopamine-treated or HVA-treated tissues and those detected in tissues that were not exposed to dopamine or HVA.

 

Figure 6
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Fig. 6. QMP-induced changes in activity. Activity levels in 4-day-old QMP-exposed bees were significantly lower than in age-matched control (untreated) bees. The effects of QMP were partially reversed by treating QMP-exposed bees with L-dopa. Data are expressed as mean activity levels ± SEM with a sample size of 20 for each group. Overall significance was determined by one-way ANOVA followed by Tukey's tests for post hoc comparisons. Letters above the bars indicate differences between groups. Groups that share a letter are not significantly different.

 


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