La Trobe
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Untargeted Metabolomic Analyses Reveal Chemical Complexity of Dioecious Cannabis Flowers

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Cannabis is a mostly dioecious multi-use flowering plant genus. Sexual dimorphism is an important characteristic in Cannabis-based commercial production systems, which has consequences for fibre, seed, and the yield of secondary metabolites, such as phytocannabinoid and terpenes for therapeutic uses. Beyond the obvious morphological differences between male and female plants, metabolic variation among dioecious flowers is largely undefined. Here, we report a pilot metabolomic study comparing staminate (male) and pistillate (female) unisexual flowers. Enrichment of the α-linolenic acid pathway and consensus evaluation of the jasmonic acid (JA) related compound 12-oxo-phytodienoicacid (OPDA) among differentially abundant metabolites suggests that oxylipin signalling is associated with secondary metabolism and sex expression in female flowers. Several putative phytocannabinoid-like compounds were observed to be upregulated in female flowers, but full identification was not possible due to the limitation of available databases. Targeted analysis of 14 phytocannabinoids using certified reference standards (cannabidiolic acid (CBDA), cannabidiol (CBD), Δ9-tetrahydrocannabinolic acid A (Δ9-THCAA), Δ9-tetrahydrocannabinol (Δ9-THC), cannabichromenic acid (CBCA), cannabichromene (CBC), cannabigerolic acid (CBGA), cannabigerol (CBG), cannabinolic acid (CBNA), cannabinol (CBN), cannabidivarinic acid (CBDVA), cannabidivarin (CBDV), tetrahydrocannabivarinic acid (THCVA), and tetrahydrocannabivarin (THCV)) showed a higher total phytocannabinoid content in female flowers compared with the male flowers, as expected. In summary, the development of a phytocannabinoid-specific accurate-mass MSn fragmentation spectral library and gene pool representative metabolome has the potential to improve small molecule compound annotation and accelerate understanding of metabolic variation underlying phenotypic diversity in Cannabis.

Funding

MSD, AB, andMTWacknowledge the support of the Australian Research Council (ARC) Linkage Program grant (LP160101317). AB, MSD, and MAD acknowledge the support of the ARC Research Hub for Medicinal Agriculture (IH180100006). Cann Group Limited are a partner organisation of the ARC linkage program grant LP160101317 and the ARC Research Hub for Medicinal Agriculture (IH180100006). The authors also acknowledge generous resource allocations from an Ian Potter Foundation grant (#31110299) and the ARC LIEF scheme grant (LE200100117) towards the purchase of the mass spectrometers. AB and MSD were supported by La Trobe University through the La Trobe Institute for Agriculture and Food (LIAF).

History

Publication Date

21/05/2021

Journal

Australian Journal of Chemistry

Volume

74

Issue

6

Pagination

p. 17 (p. 463-479)

Publisher

CSIRO PUBLISHING

ISSN

0004-9425

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