Page 164 - PC2019 Program & Proceedings

PLANT CANADA 2019

S113. Distinct metabolic modes drive monoterpenoid biosynthesis in a natural population of
Pelargonium graveolens (rose scented geranium)
Bergman, M.; M. Phillips *
(University of Toronto – Mississauga

Pelargonium graveolens is a wild predecessor to rose-scented geraniums cultivated for their essential oils,
which are useful in the cosmetics, fragrance and flavoring industries. Despite their economic uses, little is
known about the biosynthesis of Pelargonium essential oil components. Untargeted volatile profiling of
22 seed-grown wild-type P. graveolens lines and whole plant isotopic labelling studies demonstrated the
contribution of at least two distinct monoterpene biosynthetic pathways in these plants; namely, cyclic p-
menthanes such as (-)-isomenthone and acyclic monoterpene alcohols such as geraniol and (-)-citronellol
and their derivatives (referred to here as citronelloid monoterpenes). Three distinct chemotypic groups
favoring either p-menthane or citronelloid biosynthesis were defined as a result of hierarchical clustering
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analysis. CO2 isotopic labeling studies and targeted chiral GCMS analyses indicated that p-menthane
monoterpenoids in Pelargonium are synthesized via (+)-piperitone. This whole plant isotopic labeling
approach also permitted us to measure the rate of monoterpenoid biosynthesis under physiological
conditions in intact plants. Labeling in the (-)-isomenthone-rich chemotype correlated with (+)-limonene
but not its antipode, an effect absent in the citronelloid rich chemotypes, from which we conclude that
(+)-limonene is most likely the precursor to p-menthane monoterpenoids in geraniums. The absence of
(+)-pulegone in Pelargonium extracts and rapid labeling of (+)-piperitone provide evidence that p-
menthane biosynthesis in rose-scented geranium is fundamentally distinct from the related p-menthane
pathway in peppermint (Mentha x piperita) which yields (-)-menthol.

Michael Phillips (michaelandrew.phillips@utoronto.ca)

S114. Profiling anthocyanin species involved in developmentally regulated programmed cell death
in lace plant (Aponogeton madagascariensis) leaf development
2
*1
2
2
1
Denbigh, G. ; S. MacKinnon ; G. Pitcher ; H. Wright ; C. Lacroix ; A. Gunawardena
3
3
1 Dalhousie University; Agriculture and Agri-food Canada; University of Prince Edward Island
2
Programmed cell death (PCD) is a systematic method of cellular destruction and is required in plants for
normal development and survival. Lace plant (Aponogeton madagascariensis) uses PCD to form
perforations throughout its leaves and has emerged as a model organism in the study of developmentally
regulated PCD in plants. The development of perforation formation in lace plant leaves is divided into
five main stages: pre-perforation (prior to PCD initiation), window (PCD occurs), perforation formation,
perforation expansion, and mature (PCD completed). Early stage leaves are pink in colour due to
abundant anthocyanin pigmentation; the first visible sign of cell death is the disappearance of anthocyanin
in window stage leaves. Due to this conspicuous pattern of anthocyanin loss, it is suspected that these
pigments may play a role in lace plant PCD. The research objective is to profile anthocyanin species
involved in developmental PCD during lace plant leaf development. Sterile cultures of lace plant were
established, and tissues were excised for crude anthocyanin extraction. The extracts profiled via LC-DAD
and LC-MS. LC-DAD results indicated that the anthocyanin species and their relative abundances varied
with the stages of leaf development. LC-MS identified four abundant anthocyanin species present in lace
plant leaves that are not found in common fruits and vegetables. The identity of these anthocyanin species
are presently being determined.

Georgia Denbigh (g.denbigh@dal.ca)

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