过表达和敲减ame-miR-13b对意大利蜜蜂幼虫肠道内基因表达的影响

【目的】微小RNA(microRNAs, miRNAs)在昆虫的繁殖、发育和免疫等重要生命活动的调控过程中扮演关键角色。本研究旨在探究在意大利蜜蜂Apis mellifera ligustica幼虫个体水平过表达与敲减ame-miR-13b对其靶基因表达的影响,为深入探究ame-miR-13b调控意大利蜜蜂幼虫肠道发育的分子机理提供理论和实验依据。【方法】根据ame-miR-13b的核苷酸序列设计合成相应的模拟物mimic-ame-miR-13b和抑制物inhibitor-ame-miR-13b及其对照mimic-NC和inhibitor-NC,混入饲料后饲喂意大利蜜蜂3日龄幼虫,每12 h更换一次饲料,连续饲喂6次,以分别过表达和敲减ame-miR-13b;通过RT-qPCR检测过表达和敲减ame-miR-13b后意大利蜜蜂幼虫肠道中ame-miR-13b及其靶基因Ecr, Egfr和P450 18a1的表达量。【结果】与mimic-NC饲喂组相比, mimic-ame-miR-13b饲喂组中ame-miR-13b在意大利蜜蜂4和6日龄幼虫肠道中均显著上调表达;与饲喂inhibitor-NC组相比,inhibitor-ame-miR-13b饲喂组中ame-miR-13b在4日龄幼虫肠道中下调表达,在5和6日龄幼虫肠道中显著下调表达。与mimic-NC饲喂组相比,过表达ame-miR-13b组中意大利蜜蜂6日龄幼虫肠道中Egfr的表达量显著降低,而Ecr和P450 18a1的表达量均显著升高。与inhibitor-NC饲喂组相比,敲减ame-miR-13b组中意大利蜜蜂6日龄幼虫肠道中Egfr上调表达但不显著,Ecr显著上调表达,而P450 18a1显著下调表达。【结论】通过饲喂法在意大利蜜蜂幼虫个体中成功实现了miRNA的过表达和敲减;ame-miR-13b与Egfr之间存在潜在的负调控关系。     

ame-miR-79负调控意大利蜜蜂工蜂幼虫肠道中靶基因CYP450和FG的表达

【目的】本研究旨在通过饲喂ame-miR-79的模拟物(mimic)和抑制物(inhibitor)对意大利蜜蜂Apis mellifera ligustica工蜂幼虫肠道内的ame-miR-79分别进行过表达和敲减,探究ame-miR-79对幼虫肠道内靶基因表达的调控作用。【方法】通过分子克隆与Sanger测序验证意大利蜜蜂工蜂幼虫肠道内ame-miR-79的序列真实性。通过饲喂mimic-miR-79和inhibitor-miR-79对意大利蜜蜂工蜂4-6日龄幼虫肠道内的ame-miR-79分别进行过表达和敲减。采用相关生物信息学软件进行ame-miR-79的靶基因预测与分析。通过RT-qPCR检测ame-miR-79的过表达和敲减效果及过表达和敲减ame-miR-79后靶基因的相对表达量。【结果】ame-miR-79在意大利蜜蜂工蜂幼虫肠道内真实存在。与无义模拟物(nonsense mimic, mimic-NC)组相比,mimic-miR-79组的4-6日龄幼虫肠道内ame-miR-79的表达量皆极显著上调;与无义抑制物(nonsense inhibitor, inhibitor-NC)组相比,inhibitor-miR-79组的4和5日龄幼虫肠道内ame-miR-79的表达量显著下调,6日龄幼虫肠道内ame-miR-79的表达量极显著下调。ame-miR-79共靶向303个基因,涉及27个GO条目和179条KEGG通路。相较于mimic-NC组,靶基因细胞色素P450基因CYP450在mimic-miR-79组的4和5日龄幼虫肠道内均极显著下调表达,而在6日龄幼虫肠道内上调表达;靶基因fringe糖基化转移酶(fringe glycosyltransferase, FG)基因在4日龄幼虫肠道内下调表达,在5日龄幼虫肠道内显著下调表达,而在6日龄幼虫肠道内上调表达。相较于inhibitor-NC组,CYP450在inhibitor-miR-79组的4日龄幼虫肠道内极显著上调表达,在6日龄幼虫肠道内上调表达,而在5日龄幼虫肠道内下调表达;FG的表达水平在4日龄幼虫肠道内显著上调,在5和6日龄幼虫肠道内极显著上调。【结论】ame-miR-79在意大利蜜蜂工蜂幼虫肠道内真实存在;通过饲喂模拟物和抑制物能分别实现意大利蜜蜂工蜂幼虫肠道内ame-miR-79的有效过表达和敲减;ame-miR-79负调控意大利蜜蜂工蜂幼虫肠道内CYP450和FG的表达。     

ame-miR-14在意大利蜜蜂工蜂幼虫肠道发育过程的调控作用

【目的】本研究旨在揭示ame-miR-14在意大利蜜蜂Apis mellifera ligustica工蜂幼虫肠道发育过程的调控作用。【方法】通过Stem-loop RT-PCR和Sanger测序分别验证ame-miR-14在意大利蜜蜂工蜂6日龄幼虫肠道中的表达和序列真实性。饲喂ame-miR-14的模拟物(mimic-ame-miR-14)和抑制物(inhibitor-ame-miR-14)及其相应的阴性对照mimic-NC和inhibitor-NC对ame-miR-14分别进行过表达和敲降,利用RT-qPCR检测意大利蜜蜂工蜂4-6日龄幼虫肠道中ame-miR-14的表达量。利用生物信息学软件预测ame-miR-14的靶基因并进行相关分析。利用RT-qPCR检测ame-miR-14的过表达和敲降后其靶基因FoxO和Hedgehog在4-6日龄幼虫肠道中的相对表达量。【结果】ame-miR-14在意大利蜜蜂工蜂6日龄幼虫肠道中真实存在和表达。相较于饲喂mimic-NC,饲喂mimic-ame-miR-14后ame-miR-14表达量在意大利蜜蜂工蜂4-6日龄幼虫肠道中均为显著上调;相...     

吡虫啉大田使用剂量对意大利蜜蜂工蜂学习和记忆的影响

【目的】吡虫啉(imidaclorprid)是新烟碱类农药中使用最为广泛的农药种类,作用于蜜蜂脑部的烟碱型乙酰胆碱受体,此外,吡虫啉对蜜蜂生长发育有一定影响。本研究旨在明确吡虫啉大田使用剂量对蜜蜂学习、记忆行为的影响,为探明部分地区蜂群大面积死亡原因提供佐证,也可为该药田间安全使用提供参考。【方法】用油漆笔标记刚出房的1日龄意大利蜜蜂Apis mellifera ligustica工蜂,置于蜂群中8 d后取出,在室内恒温恒湿箱(30±1℃,相对湿度为40%±10%,黑暗)中笼养9 d(每盒50头),处理组自由采集含0.01 ng/μL吡虫啉的30%(w/v)糖水,对照组自由采集含0.01 ng/μL丙酮的30%(w/v)糖水。使用自制的蜜蜂气味学习设备,在3次配对的柠檬气味刺激和糖水刺激训练基础上,对18日龄蜜蜂进行气味联想性学习和记忆实验。【结果】处理组和对照组蜜蜂在为期9 d的饲喂过程中的死亡率无显著差异(P0.05)。在3次气味联想性学习实验中,与对照组相比,处理组蜜蜂在第2和第3次实验中学习能力显著降低(P0.01),而在第1次实验中无差异[喙伸反应率(PER)%=0];24 h后,处理组蜜蜂的喙伸反应率与对照组无显著差异(P0.05)。【结论】结果表明,0.01 ng/μL吡虫啉不会导致蜜蜂急性死亡;在此剂量吡虫啉作用下,蜜蜂的24 h长期记忆虽不受影响,但学习能力显著受到抑制,进而可能对蜜蜂的采集行为等产生不利影响。     

意大利蜜蜂不同日龄工蜂脑部三种miRNA的表达水平

【目的】意大利蜜蜂 Apis mellifera ligustica（简称“意蜂”）是社会性昆虫,蜂群中的工蜂表现出年龄依赖性的行为转变,其行为转变的机制一直是研究的热点。本研究分别检测了3种miRNA（ame-let-7, ame-miR-13b和ame-miR-279）在不同日龄意蜂工蜂脑部的表达情况,以期为探究意蜂工蜂年龄依赖性行为变化机制提供重要线索。【方法】通过荧光定量PCR分别检测了不同发育时期（4, 8, 12, 17, 22, 26和30日龄）意蜂工蜂脑部3种miRNA的表达情况,并检验miRNA的表达差异情况。【结果】ame-let-7的表达量随工蜂日龄的增加逐渐降低,在17日龄后其表达量趋于稳定;ame-miR-13b的表达量则随着工蜂日龄的增加逐渐增加,但在26和30日龄的工蜂中稳定表达;ame-miR-279的表达量则呈类似正态分布状态,其中在12日龄工蜂中表达量最高,且在17日龄后稳定表达。这3种miRNA表达均具有明显的时间特异性。【结论】 ame-let-7, ame-miR-13b和ame-miR-279的表达与工蜂年龄依赖性行为变化具有相关性和规律性,对于深入探究miRNA的作用位点具有重要参考价值。     

RNAi沉默王浆主蛋白1(Mrjp1)基因对意大利蜜蜂工蜂学习和记忆的影响

【目的】前期研究发现经吡虫啉处理的意大利蜜蜂Apis mellifera ligustica(简称“意蜂”)工蜂学习能力下降,转录组学分析表明王浆主蛋白1(major royal jelly protein 1, MRJP1)基因在吡虫啉处理的蜜蜂脑中显著下调,MRJP1可能参与调控蜜蜂学习能力。本研究旨在采用RNA干扰(RNAinference, RNAi)技术将Mrjp1特异性沉默,验证MRJP1在意蜂工蜂嗅觉学习中的关键作用。【方法】通过克隆技术获得Mrjp1基因cDNA 序列,经测序验证后,设计引物,合成用于RNAi干扰Mrjp1基因表达的dsRNA。注射dsMrjp1的意蜂工蜂作为处理组(dsMrjp1注射组),注射dsEGFP的意蜂工蜂作为对照组(dsEGFP注射组),随后通过伸吻反应(proboscis extension response, PER)实验比较两组的嗅觉学习与记忆能力差异。最后采用实时荧光定量PCR(quantitative real-time PCR, qRT-PCR)检测注射dsMrjp1后意大利蜜蜂工蜂脑中Mrjp1的相对表达量。【结果】dsMrjp1注射组与dsEGFP注射组意蜂工蜂学习能力差异显著,dsMrjp1注射组意蜂工蜂的学习能力显著降低。学习后2 h,两组意蜂工蜂的记忆力无显著差异。qRT-PCR结果显示Mrjp1的表达水平在dsMrjp1注射组意蜂工蜂脑中显著低于dsEGFP注射组,表明学习能力降低的处理组意蜂脑内对应的Mrjp1表达水平也降低。【结论】通过RNAi抑制意蜂工蜂Mrjp1基因的表达后,其嗅觉学习能力受到显著性抑制,但记忆力未受到显著影响,提示Mrjp1可能是调控意蜂学习的重要基因之一。本研究结果有助于后续进一步研究蜜蜂嗅觉学习相关的分子机制。     

中华蜜蜂气味受体基因AcerOr167的克隆及表达分析

本研究通过RT-PCR获得中华蜜蜂气味受体基因Or167的cDNA序列,并采用多种生物信息学软件对其结构特征进行预测分析;利用荧光定量PCR检测Acer Or167 m RNA在工蜂羽化后不同发育阶段(1、5、10、15、20、25和30日龄)和不同组织(触角、头、胸、腹、足、翅)中的相对表达量。克隆获得中华蜜蜂Or167的c DNA序列,命名为Acer Or167(Gen Bank登录号为KF239369),其全长1311 bp,编码436个氨基酸,预测有5个跨膜结构域;多序列比对结果显示,中华蜜蜂Acer Or167与西方蜜蜂Amel Or167的一致性最高,达94%,而与毕氏粗角蚁Cbir Or4-like的一致性最低,为49%;荧光定量结果显示,Acer Or167 m RNA在成蜂不同发育期的各个组织中均有表达,且触角中的表达量极显著高于其它各个组织(P0.01),在头、胸、腹、足、翅中有少量表达;从触角不同发育阶段的表达情况来看,1日龄表达量最低,5日龄表达量显著升高,20日龄表达量最高,且极显著高于其它各日龄(P0.01)。推测Acer Or167可能在中华蜜蜂的嗅觉识别系统中起着重要的作用,与中华蜜蜂外出采集,识别花香气味有关。本研究为进一步深入研究中华蜜蜂传统气味受体的功能奠定理论基础。     

氯化锂对意大利蜜蜂基于伸吻反应行为的影响

【目的】本研究旨在明确25mmol·L~(-1)氯化锂对蜜蜂蔗糖敏感性、学习和记忆行为的影响,为氯化锂作为杀螨剂应用于蜂业提供参考依据。【方法】利用50%(w/v)糖水溶液在巢门口引蜂,抓取采集糖水的蜜蜂视为采集蜂,随机分为6组对照和处理。鉴于蜜蜂对笼养环境的适应期,室内恒温恒湿箱【(30±1)℃,相对湿度为40%±10%,黑暗】中饲喂30%糖水笼养24 h(每盒50头)后,处理组和对照组分别自由采集含25 mmol·L~(-1)氯化锂的30%(w/v)糖水和30%(w/v)糖水24 h,6组中的3组用来测试对6种不同浓度糖水的敏感性(0.1%、0.3%、1%、3%、10%、30%),余下3组蜜蜂用来进行气味联想性学习实验;将收集的采集蜂不进行实验室笼养,随机分为对照和处理(35头/组),接受气味联想性学习训练,然后对蜜蜂个体饲喂10μL 30%(w/v)糖水和含25 mmol·L~(-1)氯化锂的30%(w/v)糖水,2 h后测试蜜蜂记忆。【结果】对照组和处理组在氯化锂处理24 h内死亡率无显著差异(P 0.05);糖水敏感性测试实验中,处理组对低浓度糖水(0.1%-3%)的喙伸反应率高于对照组(0.3%:P0.05;1%:P0.01;3%:P0.001),处理组的蔗糖响应分数(SRS)极显著高于对照组(P0.01);气味联想性学习实验中,两组的喙伸反应率随训练次数的增加而呈上升趋势,虽然在第二次学习中,对照组的喙伸反应率显著性高于处理组(P0.05),但两组的学习能力随训练次数增加差异减小,最终趋于一致;2 h记忆行为实验中,处理组的喙伸反应率显著高于对照组(P0.05)。【结论】结果表明,25 mmol·L~(-1)氯化锂对蜜蜂无急性致死作用;蜜蜂接触此剂量氯化锂24 h后,蜜蜂对低浓度糖水的敏感性增强,蜜蜂最终学习行为不受影响,但蜜蜂的2 h短期记忆受到积极影响,进而可能利于提高蜜蜂采集行为。     

中华蜜蜂气味受体基因AcerOR113的克隆与时空表达分析

【目的】鉴定中华蜜蜂Apis cerana cerana气味受体基因并分析其结构特征,明确其在外界蜜粉源充足和缺乏时期不同发育阶段各组织中的表达差异,以期为该基因的功能研究提供理论依据。【方法】利用RT-PCR技术从中华蜜蜂采集蜂触角中扩增获得气味受体基因的cDNA序列;利用生物信息学软件预测分析其编码蛋白的结构特性;采用MEGA6.0邻接法(neighbor-joining)构建系统进化树;利用实时荧光定量PCR技术分析该基因在不同蜜粉源条件下在中华蜜蜂不同日龄(1,5,10,15,20,25和30日龄)工蜂的不同组织(触角、头(去除触角)、胸(去除翅)、腹、足和翅)中的表达差异。【结果】从中华蜜蜂采集蜂触角中克隆获得了中华蜜蜂气味受体基因Acer OR113的cDNA序列(Gen Bank登录号:KT252877.1)。该基因的开放阅读框(ORF)长1 035 bp,编码344个氨基酸,成熟蛋白分子量为40.13 kD,理论等电点(pI)7.05,无信号肽,含有6个跨膜结构且N端位于胞内,在第59-343位氨基酸之间存在一个昆虫气味受体家族7tm-6 superfamily保守结构域。Acer OR113与西方蜜蜂Apis mellifera的Amel OR113亲缘关系最近,氨基酸序列一致性高达94%。实时荧光定量PCR结果显示,无论外界环境中蜜粉源是否充足,Acer OR113在不同日龄工蜂触角中的表达量均极显著高于其他组织(P0.01),腹部中的表达量最低;外界蜜粉源充足时各日龄工蜂触角中Acer OR113的表达量均极显著低于蜜粉源缺乏时相应日龄工蜂触角中的表达量(P0.01)。【结论】Acer OR113具有昆虫气味受体的典型特征,其基因特异性高表达于中华蜜蜂成虫触角中,且表达量在外界蜜粉源缺乏时期高于在蜜粉源充足时期,推测其主要与识别外界蜜粉源的花香气味有关。     

腺苷酸环化酶3缺失下调小鼠嗅觉受体基因表达北大核心CSCD

主要嗅觉表皮组织(MOE)是哺乳动物感知气味分子的重要器官,气味诱导是嗅觉受体神经元(ORN)活动的起点,嗅觉受体(OR)结合气味分子后通过环腺苷酸(c AMP)信号通路向下游传递信号。腺苷酸环化酶3(AC3)是此通路中的重要分子。为了探讨AC3缺失对小鼠MOE内ORs基因表达的影响,本文以AC3敲除型小鼠(AC3-/-)和野生型小鼠(AC3+/+)为材料,采用荧光定量PCR(qRT-PCR)、荧光原位杂交(FISH)技术分析了部分ORs基因及与其相关因子在MOE中的表达。qRT-PCR表明,3月龄AC3-/-小鼠MOE中嗅觉受体Olfr15、Olfr16、Olfr533、Olfr536、Olfr1507和Olfr642的表达量均显著下降。出生后PND7、PND30和PND90三个不同发育时期的AC3-/-小鼠MOE原位杂交显示,嗅觉受体Olfr15、Olfr536和Olfr1507表达的细胞数目均减少。进一步qRTPCR分析发现,3月龄AC3-/-小鼠嗅觉受体相关因子Rtp1、Rtp2、Reep1、Lhx2、Emx2和Ric-8b的表达也均发生显著下调。由此推测,AC3缺失导致的ORs及其相关因子的表达下调可能是嗅觉行为障碍的原因之一。     

The microRNA ame-miR-279a regulates sucrose responsiveness of forager honey bees (Apis mellifera)

Increasing evidence demonstrates that microRNAs (miRNA) play an important role in the regulation of animal behaviours. Honey bees (Apis mellifera) are eusocial insects, with honey bee workers displaying age-dependent behavioural maturation. Many different miRNAs have been implicated in the change of behaviours in honey bees and ame-miR-279a was previously shown to be more highly expressed in nurse bee heads than in those of foragers. However, it was not clear whether this difference in expression was associated with age or task performance. Here we show that ame-miR-279a shows significantly higher expression in the brains of nurse bees relative to forager bees regardless of their ages, and that ame-miR-279a is primarily localized in the Kenyon cells of the mushroom body in both foragers and nurses. Overexpression of ame-miR-279a attenuates the sucrose responsiveness of foragers, while its absence enhances their sucrose responsiveness. Lastly, we determined that ame-miR-279a directly target the mRNA of Mblk-1. These findings suggest that ame-miR-279a plays important roles in regulating honey bee division of labour.     

Olfactory information transfer in the honeybee: compared efficiency of classical conditioning and early exposure

We investigated the ability of honeybees, Apis mellifera, to use olfactory information gained in a given experimental context, in other contexts. First, restrained bees were subjected to a Pavlovian associative learning procedure, based on the conditioning of the proboscis extension response (PER), where a floral odour was paired with a sugar reward. We observed the orientation behaviour of conditioned and na?ve bees in a four-armed olfactometer with four contiguous fields either scented with the conditioning odour or unscented. Information transfer was clearly shown, conditioned bees orienting towards the conditioning odour, whilst na?ve bees shunned it. Second, the effect of passive olfactory exposures during the bees' development was assessed in two behavioural contexts: either orientation in the olfactometer or a PER conditioning procedure. Two exposure periods were applied: (1) the pupal stage (9 days before emergence); (2) the early adult stage (8 days after emergence). No effect of preimaginal exposure was recorded, but exposure during the early adult stage induced a higher choice frequency of the odour field in the olfactometer, and lower learning performance in the PER conditioning assay. These observations show that olfactory information gained during development can modify bees' later behaviour in different contexts: this is another instance of olfactory information transfer in bees. These results also suggest that nonassociative learning phenomena, taking place at a critical period during development, might be involved in the maturation of the bees' olfactory system, and in the organization of odour-mediated behaviours. Copyright 2000 The Association for the Study of Animal Behaviour.     

Visual associative learning in restrained honey bees with intact antennae

A restrained honey bee can be trained to extend its proboscis in response to the pairing of an odor with a sucrose reward, a form of olfactory associative learning referred to as the proboscis extension response (PER). Although the ability of flying honey bees to respond to visual cues is well-established, associative visual learning in restrained honey bees has been challenging to demonstrate. Those few groups that have documented vision-based PER have reported that removing the antennae prior to training is a prerequisite for learning. Here we report, for a simple visual learning task, the first successful performance by restrained honey bees with intact antennae. Honey bee foragers were trained on a differential visual association task by pairing the presentation of a blue light with a sucrose reward and leaving the presentation of a green light unrewarded. A negative correlation was found between age of foragers and their performance in the visual PER task. Using the adaptations to the traditional PER task outlined here, future studies can exploit pharmacological and physiological techniques to explore the neural circuit basis of visual learning in the honey bee.     

Viral Infection Affects Sucrose Responsiveness and Homing Ability of Forager Honey Bees,Apis mellifera L.

Honey bee health is mainly affected by Varroa destructor, viruses, Nosema spp., pesticide residues and poor nutrition. Interactions between these proposed factors may be responsible for the colony losses reported worldwide in recent years. In the present study, the effects of a honey bee virus, Israeli acute paralysis virus (IAPV), on the foraging behaviors and homing ability of European honey bees (Apis mellifera L.) were investigated based on proboscis extension response (PER) assays and radio frequency identification (RFID) systems. The pollen forager honey bees originated from colonies that had no detectable level of honey bee viruses and were manually inoculated with IAPV to induce the viral infection. The results showed that IAPV-inoculated honey bees were more responsive to low sucrose solutions compared to that of non-infected foragers. After two days of infection, around 10⁷ copies of IAPV were detected in the heads of these honey bees. The homing ability of IAPV-infected foragers was depressed significantly in comparison to the homing ability of uninfected foragers. The data provided evidence that IAPV infection in the heads may enable the virus to disorder foraging roles of honey bees and to interfere with brain functions that are responsible for learning, navigation, and orientation in the honey bees, thus, making honey bees have a lower response threshold to sucrose and lose their way back to the hive.     

Effect of royal jelly on longevity and memory-related traits of Apis mellifera workers

Royal jelly (RJ) is a key factor for honey bee caste determination. The queen bee is fed with RJ by worker bees throughout her life, while the worker bees eat bee bread themselves. This study was designed to explore the effect of nutrient-rich RJ on longevity and learning and memory abilities of workers of the western honey bee Apis mellifera. The newly emerged worker bees were randomly divided into three groups and were fed 50% sucrose solution containing 0%, 10%, and 20% RJ. We found that worker bees fed with 10% and 20% RJ showed significantly improved longevity and higher proboscis extension response success rate compared to bees fed with 50% sucrose containing 0% RJ. Additionally, bees fed with 20% RJ showed significantly higher level of expression of memory related genes (GluRA and Nmdar1) compared to the control group. Furthermore, expression of the Nmdar1 gene of worker bees fed with 10% RJ was also significantly higher than in the control group. These results indicate that RJ has potential effects on the longevity and learning and memory abilities of A. mellifera.     

Social learning of floral odours inside the honeybee hive

A honeybee hive serves as an information centre in which communication among bees allows the colony to exploit the most profitable resources in a continuously changing environment. The best-studied communication behaviour in this context is the waggle dance performed by returning foragers, which encodes information about the distance and direction to the food source. It has been suggested that another information cue, floral scents transferred within the hive, is also important for recruitment to food sources, as bee recruits are more strongly attracted to odours previously brought back by foragers in both honeybees and bumble-bees. These observations suggested that honeybees learn the odour from successful foragers before leaving the hive. However, this has never been shown directly and the mechanisms and properties of the learning process remain obscure. We tested the learning and memory of recruited bees in the laboratory using the proboscis extension response (PER) paradigm, and show that recruits indeed learn the nectar odours brought back by foragers by associative learning and retrieve this memory in the PER paradigm. The associative nature of this learning reveals that information was gained during mouth-to-mouth contacts among bees (trophallaxis). Results further suggest that the information is transferred to long-term memory. Associative learning of food odours in a social context may help recruits to find a particular food source faster.     

Olfactory interference during inhibitory backward pairing in honey bees

Background

Restrained worker honey bees are a valuable model for studying the behavioral and neural bases of olfactory plasticity. The proboscis extension response (PER; the proboscis is the mouthpart of honey bees) is released in response to sucrose stimulation. If sucrose stimulation is preceded one or a few times by an odor (forward pairing), the bee will form a memory for this association, and subsequent presentations of the odor alone are sufficient to elicit the PER. However, backward pairing between the two stimuli (sucrose, then odor) has not been studied to any great extent in bees, although the vertebrate literature indicates that it elicits a form of inhibitory plasticity.

Methodology/Principal Findings

If hungry bees are fed with sucrose, they will release a long lasting PER; however, this PER can be interrupted if an odor is presented 15 seconds (but not 7 or 30 seconds) after the sucrose (backward pairing). We refer to this previously unreported process as olfactory interference. Bees receiving this 15 second backward pairing show reduced performance after a subsequent single forward pairing (excitatory conditioning) trial. Analysis of the results supported a relationship between olfactory interference and a form of backward pairing-induced inhibitory learning/memory. Injecting the drug cimetidine into the deutocerebrum impaired olfactory interference.

Conclusions/Significance

Olfactory interference depends on the associative link between odor and PER, rather than between odor and sucrose. Furthermore, pairing an odor with sucrose can lead either to association of this odor to PER or to the inhibition of PER by this odor. Olfactory interference may provide insight into processes that gate how excitatory and inhibitory memories for odor-PER associations are formed.