March/April 2023 - 18

A team approach
Information about the identification and
synthesis of leptotriene was published in July
2022. By making the information public, it is freely
available to companies that produce pheromone
products. An American company has already
synthesized leptotriene using Millar's route, and
the team plans to work with the company to move
pheromone lures for Leptoglossus species from
the research phase to a practical commercial
product, readily available to growers.
Many members of the Millar lab contributed to
chemistry work, including:
* Professor Jocelyn Millar (identification of the
compound, determination of the synthetic
strategy to use and overall supervisor of the lab)
* Dr. Yunfan Zou (carried out and optimized the
synthesis of leptotriene)
* Dr. Sean Halloran (reared the insects,
prepared and analyzed pheromone
extracts using gas chromatography-mass
spectrometry and gas chromatographyelectroantennographic
* Dr. Tessa Shates (graduate student who helped
field collect insects and carried out volatile
collections for her first two years)
separates chemical mixtures and provides information
about their structures) to help identify the possible
components of the pheromone.
In parallel, they used gas chromatography coupled
to electroantennogram assays, which use a live insect
antenna as a detector. These assays show exactly which
compounds in an extract the antenna is most sensitive
to, i.e., the components which are most likely to be
pheromones. The researchers can then focus their
identification efforts on those components.
However, one drawback of this type of assay is that it
only shows that the insect detects the chemical. It does not
indicate whether the chemical is an attractant or a repellent.
" What we ultimately found is that this pheromone
might contain as many as nine different compounds. After
we identified each of these compounds, we subsequently
needed to figure out a process to synthesize them in
quantities sufficient for field testing, " said Wilson.
Pheromones from sexually mature male bugs
being analyzed with a gas chromatographmass
The hidden compound
Millar and his team were able to identify a
hidden compound that barely showed up on the gas
chromatograph but elicited a very strong response from
bug antennae in electroantennogram assays and was
therefore likely to be a key component of the pheromone
blend. However, it was only present in small amounts as
part of a mixture of many other compounds, and it was a
compound new to science.
Essential collaborators for field work are:
* Dr. Houston Wilson (collected bugs to start lab
colonies and carried out all the field trials)
* Dr. Kent Daane (collected bugs to start lab
colonies and advised on all field work)
In addition, the California team joined forces with
Professor David Hall of Greenwich University in the
U.K., and his Spanish collaborators Professor Juan A.
Pajares and student Laura Ponce-Herrero, to work
on the pheromone for the related Leptoglossus
occidentalis, which also turned out to use leptotriene
as a pheromone component. Leptoglossus occidentalis
is native to North America, but it has invaded Europe,
where it is causing major damage in crops such as
edible pine nuts.

March/April 2023

Table of Contents for the Digital Edition of March/April 2023

March/April 2023 - 1
March/April 2023 - 2
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