Page 245 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

*[P83] VARIATION IN LODGING TRAITS AND TRANSCRIPTIONAL REGULATION OF GIBBERELLIN
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METABOLISM GENES IN WHEAT. Gurnoor Kaur , Ginelle Grenier , Douglas J. Cattani , Pham Anh
Tuan , and Belay T. Ayele . Department of Plant Science, University of Manitoba, Winnipeg, Manitoba,
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Canada
Correspondence to: kaurg36@myumanitoba.ca

Wheat yield and quality are negatively affected by numerous factors including lodging, which refers to
permanent displacement of a plant from its upright position that results in falling over of the plant or
breakage of the stem. Plant height and stem mechanical strength are two of the major morphological
traits that regulate lodging resistance. Crop management practices such as nitrogen fertilization affect
these morphological traits and therefore the incidence of lodging. This study investigates if variation in
lodging related morphological traits is associated with transcriptional regulation of gibberellin (GA)
metabolism genes by using two wheat cultivars with contrasting plant heights that were grown under
different nitrogen fertilization levels. Our data shows that elevated nitrogen levels resulted in 26% to 32%
increase of plant height, 2.0- to 2.5-fold increase of bending moment and 1.8- to 2.7-fold increase of
lodging index in both cultivars. However, the taller cultivar exhibited taller plant height, and higher bending
moment and lodging index than the shorter cultivar. Changes in these morphological traits due to
elevated nitrogen fertilization were associated with enhanced expression levels of the GA biosynthesis
genes, TaGA20ox4 and TaGA3ox3, and repression of the GA catabolism gene, TaGA2ox3. Treatment of
the tall cultivar plants with a GA biosynthesis inhibitor led to the reduction of plant height by 10% to 22%
irrespective of nitrogen fertilization levels. This decrease in plant height was associated with a reduction
in bending moment by 26% to 37%, which led to a decrease in lodging index by ~25%.

*[P84] UNRAVELING THE INTERPLAY BETWEEN PHENYLPROPANOID BIOSYNTHESIS AND
SALICYLIC ACID SIGNALING PATHWAYS IN MEDIATING PLANT IMMUNITY. K. A. Dinithi
Kumarapeli, Ken Wilson, and Yangdou Wei. Department of Biology, University of Saskatchewan, 112
Science Place, Saskatoon, SK, Canada, S7N 5E2
Correspondence to: wzy930@usask.ca

The plant shikimate pathway is the entry to the biosynthesis of salicylic acid (SA) and phenylpropanoids.
In Arabidopsis, SA, a key defense hormone, is predominantly synthesized through the isochorismate
synthase (ICS1) pathway, with a partial residual amount synthesized through the phenylpropanoid
pathway via the entry-point enzyme phenylalanine ammonia-lyase (PAL). PAL serves as a common
precursor for partial SA biosynthesis and the formation of a whole set of phenolic metabolites, including
monolignols, flavonoids, and phenolic esters. Monolignols contribute to lignin formation, providing a
physical barrier against pathogen penetration, while SA acts as a signaling molecule orchestrating
various defense responses. Our comparison of RNA-Seq-based transcriptome analysis revealed that
upon pathogen infection, Arabidopsis mutant plants defective in cinnamate 4-hydroxylase (C4H), which
catalyzes the second step of the general phenylpropanoids exhibited the delayed expression of
pathogenesis-related genes (a marker for pathogen-induced SA production), suggesting a regulatory link
between the two branches of shikimate pathways in mediating plant immunity. In this study, we generated
a double mutant (ics1/c4h) with impaired SA production and phenylpropanoid biosynthesis to investigate
the interplay between ICS1-mediated SA production and C4H-mediated phenylpropanoid metabolism in
plant immune responses. Pathogenicity assays revealed increased susceptibility to the adapted powdery
mildew (Erysiphe cruciferarum) in these double mutants, highlighting the significance of the coordination
between two pathways in plant defense. Further research will emphasize on fine genetic dissection of
C4H-mediated phenylpropanoid metabolisms and their associated molecular and cellular mechanisms
that contribute to plant immunity.

[P85] THE EFFECT OF COPPER-INDUCED OXIDATIVE STRESS ON THE SYMBIOSIS BETWEEN

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MODEL LEGUME LOTUS JAPONICUS AND MESORHZOBIUM LOTI. Kathryn Lamoureux and Sheila
M Macfie . Department of Biology, University of Western Ontario, London, ON, Canada, N6A 5B7
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Correspondence to: klamour2@uwo.ca

Legumes play an essential role in the nitrogen cycle due to their ability to fix atmospheric nitrogen (N). N-
fixation is carried out by symbiotic bacteria called rhizobia, housed in root nodules. Rhizobia are

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