University of Hawaiʻi at Mānoa: New research uncovers brain circuit in fruit fly that detects anti-aphrodisiac
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The decision to mate is influenced by pheromones which
are detected by taste and smell. Photo credit: Klaus Dreisewerd and Joanne Yew
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In the natural world, sense of taste controls many
behavioral decisions. For many animals, pheromones, which are chemical signals
used for communication, influence the choice to mate. However, very little is
known about how taste pheromones are processed in the brain.
The recent work by Joanne Yew, assistant researcher
at PBRC, and colleagues explicitly tracked this process—identifying the
taste cells on the fruit fly’s legs which detect the pheromone, locating the
neurons in the brain which respond to the pheromone and mapping the connection
between the two populations of cells.
Finding the ‘taste cells’
The pheromone, named CH503, is produced by males, passed
to females during mating, and stops other males from mating with the female’it
is an anti-aphrodisiac for other males.
Many taste cells are found on the forelegs of flies, so
Yew and colleagues used genetic manipulation to turn off activity in individual
classes of these taste cells. They then tested whether males could still
respond to the pheromone. Using this strategy, they were able to identify one
class of taste receptors, called Gr68a, that is responsible for detecting the
pheromone.
“Normally, males are repulsed by females that have been
perfumed with the pheromone. However, when activity in Gr68a neurons is turned
off, males will actively try to mate with females perfumed with the pheromone,”
said Yew.
Finding
the brain’s ‘detection cells’ and the chemical connectivity
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The neural pathway that control the perception of a taste
pheromone has been genetically labelled with a fluorescent protein. Photo
credit: Meredith Calvert and Kah Junn Tan
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Next, the researchers turned off activity in different
groups of cells in the central brain to determine whether males could still
respond to the pheromone. One group of cells which produces the chemical
Tachykinin appeared to be essential for detecting the pheromone.
Finally, the scientists established that the Gr68a
neurons in the leg connect with the Tachykinin neurons in the brain. To do
this, they introduced two sensors into the Gr68a and Tachykinin neuron
populations. The sensors light up when neurons in the region are close enough
to form connections. The researchers were able to detect connectivity between
the two populations of neurons.
“This work identifies a molecular signal, Tachykinin,
that controls the perception of taste pheromones and provides an anatomical map
of where this information is processed in the brain,” said Yew. “By
understanding the cellular basis of how taste information is encoded, we will
be able to study how sensory signals shape programmed behaviors and influence
complex social decisions such as the choice to mate. Potentially, we could
devise a way to manipulate Tachykinin in pest populations to control
reproduction.”
In the future, Yew and colleagues intend to further map
the connections of Tachykinin neurons and examine how physiological state
(e.g., hunger, stress) can influence the choice to mate via the Tachykinin
pathway.
Source - www.hawaii.edu
