Page 163 - PC2019 Program & Proceedings

PLANT CANADA 2019

S111. Investigating transport of seco-iridoids in Catharanthus roseus
1
2
Dastmalchi, M. ; Y. Qu ; V. De Luca 1
1 Brock University
2 University of New Brunswick

Decades of research has resolved the biosynthesis of monoterpenoid indole alkaloids (MIAs) and the anti-
cancer drugs vincristine and vinblastine in Catharanthus roseus. Studies suggest that MIA biosynthesis is
highly compartmentalized in organelles (e.g. plastids and vacuoles) and in, at least, three specialized
tissue-types. Spatial separation of distinct metabolic branches requires the translocation of intermediates
across organelle and cell boundaries. While components of the transport system, such as vacuolar efflux,
have been isolated, an accurate model of the whole transit network has eluded researchers. We identified
a transcript encoding a putative transporter from an EST database. Gene expression was suppressed in C.
roseus using virus induced gene silencing (VIGS), resulting in reduction of the seco-iridoid, secologanin
and the MIA, catharanthine in leaf extracts. Secologanin is coupled with tryptamine in the vacuole to
form the MIA backbone, strictosidine. The reduction in secologanin and catharanthine levels, suggests a
potential bottleneck early in the iridoid branch. To dissect this metabolic phenotype, we characterized the
subcellular localization of the protein using fluorescence confocal microscopy. The transporter was
heterologously expressed in yeast and assayed for substrate acceptance of iridoid intermediates. This
novel transporter appears to work with other transporter families to orchestrate biosynthesis in the seco-
iridoid pathway. The transporter could be deployed in the microbial reconstitution of MIA pathways to
add a layer of control and complexity.

Mehran Dastmalchi (mehran.dastmalchi@gmail.com)

S112. Mitragyna speciosa – a promising player in the opioid crisis
Moeller, E.; L. Virta; K. Theriault; J. Manduca; M. Perreault; T. Akhtar
University of Guelph

Mitragyna speciosa, also known as ‘Kratom’, is a tropical tree species native to South East Asia where
herbal preparations of Kratom leaves haves been used since antiquity to treat various ailments, including
opioid addiction. Approximately twenty different alkaloids have been reported to accumulate within
Kratom leaves, of which mitragynine shows the most promise as a potential opioid replacement. While
Kratom continues to receive much world-wide attention, there is still a gap in our knowledge about the
growth and propagation of the plant as well as how the accumulation of its various alkaloids changes
throughout plant development. Moreover, almost nothing is known about how Kratom alkaloids impact
areas of the brain that are associated with drug addiction and abuse liability. Accordingly, we report here
the development of a method for vegetative propagation of Kratom with over a 90% rooting rate and
define the peak accumulation times for the various therapeutic alkaloids during leaf development. Finally,
it was demonstrated that acute mitragynine exposure (10 mg/kg, i.p.) to rats resulted in a moderate but
significant suppression of theta and gamma neural oscillations selectively in cortical sub-regions of the
brain, with no effects within the reward pathway that mediates addiction. These findings support a lack of
abuse potential for mitragynine.

Emily Moeller (moellere@uoguelph.ca)

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