Page 154 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

Poplar (Populus tremula × Populus tremuloides) was chosen as our study species because poplars
produce a wide range of phenolic compounds and abundant PAs, including in roots. We utilized
previously generated transgenic poplar lines with contrasting root PA concentrations, created by
overexpression of MYB transcription factors that activate or repress the PA pathway. Wild type, and high-
and low-PA lines were inoculated with the ectomycorrhizal fungus Laccaria bicolor or the arbuscular
mycorrhizal fungus Rhizophagus irregularis. A non-inoculated control treatment was included. Plants
were grown in a sandwich culture system that allows co-culture of the mycorrhizal fungi and roots, or
inoculated with the fungi in soil in a greenhouse experiment. Uptake rates of ammonium and nitrate by
control and inoculated roots were measured using a microelectrode ion flux measurement system
TM
(MIFE ), a non-invasive method that measures net flux of specific nutrient ions at precise root locations,
and by N-labelling.
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The poplar line with low levels of PAs and other flavonoids in shoots also had relatively low root PA
concentrations. This line was less colonized by ectomycorrhizae in sandwich and soil culture. No
colonization by arbuscular mycorrhizae was evident for any poplar line. Plants from all lines inoculated
with Laccaria had lower survival and root PA concentrations than controls and plants inoculated with
Rhizophagus. Ammonium and nitrate net fluxes were low in sandwich culture roots, except in roots
inoculated with arbuscular mycorrhizae, which showed significant ammonium efflux. To confirm these
trends, measurements of N uptake by sandwich culture roots, and of ammonium and nitrate fluxes in
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soil-grown roots are in progress. Understanding the effects of the interaction of root PAs and mycorrhizal
fungi on mycorrhizal colonization and N uptake will contribute to our knowledge of ecological and
physiological impacts of PAs in the rhizosphere.

*[O104] A PROMOTER FOR THE METABOLIC ENGINEERING OF GLANDULAR TRICHOMES IN
LAVENDER. Reza Sajaditabar and Soheil Mahmoud . Department of Biology, The University of British
1 1
1
Columbia: Okanagan Campus, 3333 University Way, Kelowna, BC, Canada, V1V 1V7
Correspondence to: soheil.mahmoud@ubc.ca

Lavenders produce abundant, high-quality, terpene-rich essential oils (EO) in glandular trichomes (GT)
present on the surfaces of the above-ground plant parts. In these glands, terpene synthases (TPS), the
enzymes responsible for terpenes synthesis, are specifically and strongly expressed. Lavenders
represent excellent candidates as bioreactors for metabolic engineering to produce high-value terpenes.
However, the common approach of overexpressing genes under the control of constitutive promoters
such as the CaMV35s promoter has been problematic as it often adversely affects plant health,
presumably due to the cytotoxic effects of metabolites produced in non-GT plant cells. To address this,
GT-specific promoters offer an alternative, enhancing transgene expression exclusively in GT. This study
aims to engineer terpene metabolism in GT of Lavandula latifolia using GT-specific promoters including
those corresponding to the linalool synthase (LINS) and 1,8 cineol synthase (CINS) genes, which are
strongly and specifically expressed in lavender GTs. Lavandula latifolia leaves were transformed with
Agrobacterium tumefaciens strains containing different fragments of LINS and CINS promoters fused to
the gusA reporter gene, which encodes β-glucuronidase (GUS) enzyme. Plants in which GUS expression
is driven by the CaMV35s promoter serve as positive control. Transformed plants are being evaluated for
GUS expression. Preliminary results indicate that several promoters can drive gene expression in L.
latifolia in GTs.

*[O105] SOYBEAN CYTOCHROME P450S AND THE MAKING OF ALIPHATIC SUBERIN
1
MONOMERS. Lorena S. Yeung , Delicia Wong , Sangeeta Dhaubhadel , and Mark A. Bernards .
1,2
1
1
1 Department of Biology, Western University, London, ON, N6A 5B7, Canada; and London Research and
2
Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford St, London, Ontario, N5V 4T3,
Canada
Correspondence to: syeung96@uwo.ca

Suberin is a phenolic-lipophilic biopolymer that functions as a physical barrier to protect plants from
desiccation and pathogen infection. Soybean (Glycine max [L.] Merr) cultivars with varying amounts of
root suberin show differential resistance to root pathogens (more suberin = stronger partial resistance),
making suberin a potential focus for the production of enhanced crops. 18-hydroxyoleic acid and 18-
dicarboxylic acid are two of the most prominent aliphatic suberin monomers in soybean. Production of
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