Genomics of Moth Chemoreception
(Bombyx mori) genome remains
the first and only lepidopteran genome currently available.
Chemoreceptor genes are highly divergent and their expression levels
can be very low.
Indeed, significant progress in this
the advent of whole genome sequencing. We are using the silkworm genome
(Chinese project /
as a model to address basic and applied research questions in the order
Host Plant Selection and
and caterpillars use their sense of olfaction to locate and orient to
potential host plants. Contact chemoreptors (gustation) on the front
tarsi and ovipositor of female moths, and on the caterpillar
mouthparts, largely arbitrate host plant selection for
feeding and oviposition. We are annotating and functionally
characterizing silkworm odorant and gustatory receptors that mediate
these behaviors. We have identified several odorant receptors that are
expressed at higher levels in female moth antennae that may be involved
in detecting key host plant volatiles or male produced sex pheromones
et al., 2007). In collaboration with Richard Newcomb
New Zealand) we are characterizing the ligand binding
specificity of these female-biased receptors expressed in Sf9 cells
(activation is measured by calcium imaging).
We have also identified a silkworm
odorant receptor lineage that is
expressed in the larval antennae, which may be involved in host
selection. Using olfactory bioassays we have
found that neonate silkworms prefer the smell of (and crawl towards)
new mulberry leaves (QuickTime
Movie Clip 1-large file!) or mature leaves with feeding damage (QuickTime
Movie Clip 2-large file!).
The last half of Clip 2 shows neonate larvae crawling towards
a mature mulberry leaf with feeding damage even though the damage is
hardly visible in the video. Allison Mooney is working on this topic as
an undergraduate research project and we are analyzing SPME-collected
volatiles on a GC-MS. Neonate attraction
to odors from mature leaves, mature leaves with feeding damage and new
leaves will be tested using a custom-built olfactometer.
odors will be screened against the larval specific receptors expressed
We have demonstrated significant
orthology of Ors from
different lepidopteran families (Wanner
et al., 2007) and we are using
this to extend our research to significant pest species (USDA
Funded Project Proposal).
olfactory system of male moths is highly sensitive to the
female-produced sex pheromones. The chemistry of lepidopteran sex
pheromones has been extensively studied and has yielded many
significant tools for the management of insect pests. We now know that
the lepidopteran pheromone receptors form a conserved
subfamily. We are
using degenerate PCR, high-throughput sequencing (454
Sciences platform), and in vitro functional assays to identify and
characterize the pheromone receptors of several economically important
pest species (collaborators include Stephen
Garczynski and Thomas
Unruh, USDA-ARS, Wapato WA).
There are many future applications of
this research. Receptors that mediate critical pest behaviors can be
screened in vitro in a pharmacological approach to identify better
attractants or deterrents that can be used in traps or baits.
High-throughput in vitro assays will provide a “receptor to behavior”
approach to identifying important semiochemicals.
Furthermore this research will provide the basis to address many
fascinating questions relating to the ecology of plant-insect
interactions and the evolution of their chemosensory systems, such as
plasticity of the gustatory system in response to feeding experience