Page 107 - ACHEMS 2012 PROGRAM

molecules on the receptor may establish the interactions with
different sweeteners during a cooperative binding process for sweet
taste enhancement. Our data provide some molecular evidence for
the mechanism of PAM selectivity on the human sweet taste
receptor.
#P240 POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Logic of glycerol input to behavioral output in Drosophila
Zev Wisotsky1, Adriana Medina2, Erica Freeman3,
Anupama Dahanukar1,2,3
1University of California/Interdepartmental Neuroscience Program
Riverside, CA, USA, 2University of California/Department of
Entomology Riverside, CA, USA, 3University of
California/Bioengineering Interdepartmental Graduate
Program Riverside, CA, USA
In Drosophila, sweet taste recognition is mediated by Gr5a and
Gr64a that belong to a highly conserved clade within a large family
of Gustatory receptors (Gr)s. Other receptors in this clade are also
expressed in sweet-sensing neurons, but their function is poorly
understood. Moreover, little is known about how stimuli such as
beer, typically not rich in sugars, trigger highly attractive gustatory
responses in Drosophila. We recently found that Gr64e, a receptor
in the sweet clade, plays an essential role in feeding preference for
beer and yeast fermentation products. We identified that Gr64e is
necessary for neuronal and behavioral responses to an abundant
component of yeast and fermentation products, glycerol. Moreover,
ectopic expression of the Gr64e receptor in the CO2-sensing
olfactory neuron is sufficient to confer glycerol sensitivity.
Drosophila species that carry a polymorphism disrupting Gr64e
function have reduced behavioral preference for beer, suggesting
that Gr64e may contribute to specific evolutionary variations in
appetitive selectivity. Expression analysis shows that Gr64e-GAL4
broadly labels multiple classes of taste neurons displaying distinct
representation patterns in the brain. This observation presents an
opportunity to dissect the behavioral contribution of subsets of
glycerol-sensing neurons by selectively silencing or rescuing Gr64e
subpopulations using a collection of sweet Gr promoter-GAL4
drivers. We have already tested a number of different neuronal
subsets and are now constructing transgenic tools for finer
manipulations. Our studies will enable us to map specific aspects of
feeding behavior to glycerol taste circuits, and reveal the extent to
which the temporal sequence of sensory neuron activation
in different taste organs plays a role in feeding behavior.
Acknowledgements: Whitehall Foundation (2010-12-42)
and NSF-IGERT in Video Bioinformatics (DGE0903667).
#P241 POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Spatiotemporal Coding in Gustatory Receptor Neurons
Sam A Reiter, Mark A Stopfer
National Institute of Child Health and Development
Bethesda, MD, USA
The gustatory system allows animals to perceive a vast array of
chemical tastants, and to use this information to guide behavior.
Despite its vital role, it remains unclear how gustatory information
is processed by successive populations of neurons within the brain.
We are studying this question in an insect, the moth Manduca
sexta, which is capable of complex gustatory behaviors but
possesses a relatively simple nervous system. To explore how
gustatory information is represented within the population of
gustatory receptor neurons (GRNs) and within their follower
neurons we designed a novel apparatus that delivers pulses of
tastant at different concentrations with temporal precision. This
device allowed us to make the first intracellular recordings from
GRNs. GRNs vary greatly in levels of spontaneous activity, and in
responsiveness to the number, identity, and concentration of
tastants. Tastant application excites some GRNs, inhibits others,
and causes still others to respond with reliable sequences of
excitation and inhibition. Interneurons immediately downstream
from the GRNs remain uncharacterized. To understand how the
tastant responses of GRNs are integrated and possibly reformatted
downstream, we are also recording from and morphologically
characterizing neurons in the Sub Esophogeal Ganglion, the
primary gustatory center of the moth. Gustatory interneurons
exhibit a wide range of tastant response profiles that include
temporally complex firing patterns with multiple periods of
excitation and inhibition. Our results suggest that the early
gustatory system, like the olfactory system, employs an across
fiber pattern code that utilizes time as well as neural identity as
variables to encode the identity and concentration of tastants.
Acknowledgements: intramural grant from NIH–National Institute
of Child Health and Human Development (NICHD)
#P242 POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Topology and Functional Analysis of BmGr8, a Bombyx
mori Gustatory Receptor
Stephen C. Trowell 1, 2, Hui-Jie Zhang1,2,3, Alisha R. Anderson1,2,
A-Rong Luo2, Zhong-Huai Xiang3, Qing-You Xia3,4
1CSIRO Food Futures Flagship CANBERRA, Australia,
2CSIRO Ecosystem Sciences CANBERRA, Australia,
3The Key Sericultural Laboratory of Agricultural Ministry,
Southwest University CHONGQING, China, 4Institute of Agronomy
and Life Science, Chongqing University CHONGQING, China
“Sugar” and “bitter” receptors comprise two large clades in insect
gustatory receptor (GR) phylogeny. Based on homologies with
identified receptors, we identified five sugar receptors and a large
number of putative bitter receptors from the genome of the
lepidopteran Bombyx mori . Despite almost 60 putative sugar GRs
being identified across all sequenced insect genomes, ligands have
only been assigned to a few of the Drosophila and one of the B.
mori receptor sequences. BmGr8, a silkmoth gustatory receptor
from the sugar receptor subfamily, was expressed in insect cells.
Functional analysis, using a modified calcium-imaging assay,
showed that BmGr8 can function independently in Sf9 cells and
Abstracts | 107
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