Spatiotemporal Coding of Individual Chemicals by the Gustatory System

Reiter, Sam; Rodriguez, Chelsey Campillo; Sun, Kui; Stopfer, Mark

doi:10.1523/jneurosci.3802-14.2015

Cited by 48 publications

(63 citation statements)

References 73 publications

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“…A cellular taste coding mechanism, called the labeled line model, would apply in cases in which distinct taste qualities, are each sensed by different receptor cells, which communicates, uninterrupted to the brain. This differs from a distributive model, in which taste receptor cells respond to multiple types of taste qualities to varying amounts, and the brain then interprets the taste quality based on the intensity of the repertoire of the cellular activities [29][30][31]. Detection of saponin in food, through Gr28b.c leads to a negative behavioral valence-gustatory repulsion.…”

Section: Discussionmentioning

confidence: 98%

Gustatory receptor 28b is necessary for avoiding saponin in Drosophila melanogaster

2019

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Saponins function as a natural self‐defense mechanism for plants to deter various insects due to their unpleasant taste and their toxicity. Here, we provide evidence that saponin from Quillaja saponaria functions as an antifeedant as well as an insecticide to ward off insects in both the larval and the adult stages. Using a behavioral screen of 26 mutant fly lines, we show that the Gr28b gene cluster plays a role in saponin avoidance in the labellum. The Gr28b mutant does not avoid saponin and exhibits increased lethality when fed saponin‐mixed food. Tissue‐specific rescue experiments with five different Gr28b isoforms revealed that only the Gr28b.c isoform is required for saponin sensation. We propose that in contrast to sensing many other bitter compounds, saponin sensing does not require the function of core taste receptors, such as GR32a, GR33a, and GR66a. Our results reveal a novel role for GR28b in taste. In addition, the ability of saponin to act as insecticides as well as antifeedants suggests its potential application in controlling insect pests.

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Section: Discussionmentioning

confidence: 98%

Gustatory receptor 28b is necessary for avoiding saponin in Drosophila melanogaster

2019

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“…Secondary metabolites can also be phagostimulatory to insect pollinators, but this seems to be limited to insects that specialize on feeding on toxic plants as larvae. Adult hawk moths (Manduca sexta) find low concentrations of caffeine or lobelline phagostimulatory when they are presented to the mouthparts (Reiter et al 2015). Other lepidopteran adults that specialize on consuming plants with highly toxic alkaloids, such as the danaid butterfly, Euploea mulciber, also find alkaloids from their host plants phagostimulatory (Honda, Honda & Omura 2006).…”

Section: Nectar Chemicals Mediating Behaviour Of Pollinatorsmentioning

confidence: 99%

Plant secondary metabolites in nectar: impacts on pollinators and ecological functions

2016

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Summary1. The ecological function of secondary metabolites in plant defence against herbivores is well established, but their role in plant-pollinator interactions is less obvious. Nectar is the major reward for pollinators, so the occurrence of defence chemicals in the nectar of many species is unexpected. However, increasing evidence supports a variety of potential benefits for both plant and pollinator from these compounds. 2. Beneficial effects may include: (i) mediating specialization in plant-pollinator interactions, (ii) protecting nectar from robbery or larceny and (iii) microbial activity including preservation of nutrients in nectar from degradation and reduction in disease levels in pollinators. 3. Secondary metabolites in nectar can be toxic or repellent to flower visitors, but equally they can go undetected or even make nectar more apparent or attractive. These biological effects are concentration dependent, so must be considered at a range of ecologically relevant doses. For example, caffeine occurs in nectar and improves honeybee memory for odours associated with food rewards, which enhances pollen transfer at naturally occurring concentrations but is repellent to honeybees at higher concentrations. 4. This review synthesizes evidence from recent literature that supports selection for secondary metabolites in floral nectar as an adaptation that drives the co-evolution between plants and their pollinators. However, their presence in nectar could still simply be a consequence of their defensive role elsewhere in the plant (pleiotropy). We highlight the need for more studies demonstrating measurable benefits to the plant, the importance of exposure levels and effects on target species beyond the current emphasis on alkaloids and bees.

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“…Thus the presence of ON and OFF responses to tastants may be important for the generation of behavior in insects. A study in moths reported that second-order taste neurons show dynamic, time-varying responses, including OFF responses (Reiter et al, 2015). However, the timing of gustatory responses has not been examined in the fruit fly Drosophila melanogaster.…”

Section: Introductionmentioning

confidence: 99%

Individual bitter-sensing neurons inDrosophilaexhibit both ON and OFF responses that influence synaptic plasticity

Devineni

Deere

Sun

2020

Preprint

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The brain creates internal representations that translate sensory stimuli into appropriate behavior. Most studies of sensory processing focus on which subsets of neurons are activated by a stimulus, but the temporal features of the neural response are also important for behavior. In the taste system, the timing of peripheral sensory responses has rarely been examined. We investigated the temporal properties of taste responses in Drosophila melanogaster and discovered that different types of taste sensory neurons show striking differences in their response dynamics. Strong responses to stimulus onset (ON responses) and offset (OFF responses) were observed in bitter-sensing neurons in the labellum, whereas bitter neurons in the leg and other classes of labellar taste neurons showed only an ON response. Individual bitter labellar neurons generate both the ON and OFF responses through a cell-intrinsic mechanism that requires canonical bitter receptors. The bitter ON and OFF responses at the periphery are propagated to dopaminergic neurons that innervate the mushroom body and mediate aversive learning. When bitter is used as a reinforcement cue, the bitter ON and OFF responses can drive opposing types of synaptic plasticity and the effect of the OFF response dominates, likely due to the rapid and preferential habituation of the ON response. Together, these studies characterize novel features of neural responses in the taste system and reveal their importance for neural circuit function.

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Spatiotemporal Coding of Individual Chemicals by the Gustatory System

Cited by 48 publications

References 73 publications

Gustatory receptor 28b is necessary for avoiding saponin in Drosophila melanogaster

Gustatory receptor 28b is necessary for avoiding saponin in Drosophila melanogaster

Plant secondary metabolites in nectar: impacts on pollinators and ecological functions

Individual bitter-sensing neurons inDrosophilaexhibit both ON and OFF responses that influence synaptic plasticity

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