Page 156 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

walls of some tissues with suberin, a hydrophobic polymer regulated by the stress phytohormone abscisic
acid (ABA). Root suberin can limit root pathogen colonization in crops like soybean (Glycine max). Soybean
is a globally important oilseed crop that is susceptible to drought and salt stress. Current literature has
shown that the soybean microbiome can support abiotic stress tolerance, while root suberin provides biotic
stress tolerance The primary objective of this research was to determine root suberin-microbiome
relationship in early soybean development and if that relationship is phytohormone-dependent.

Three soybean cultivars with varying degrees of pathogen tolerance (low = OX20-8, moderate = Amsoy 71,
high = Conrad) were grown in micropropagation containers with and without microbiome treatment. The
total suberin content was measured for each cultivar at three time points in early vegetative development
(emerged cotyledons, unifoliate leaves, first trifoliate leaves). Root and rhizosphere microbiomes were
subject to metagenomic sequencing to identify suberin-associated microbiota across these soybean
cultivars. To test whether the role of phytohormones in these plant-microbe interactions, we replicated the
microbiome experiment for the Conrad cultivar with the addition of fluridone, an ABA biosynthesis inhibitor.

Current results indicate that only the Conrad cultivar, with high pathogen tolerance, increases suberization
in response to microbiome treatment early in plant development. This increase in suberin content did not
occur in Conrad plants treated with fluridone, suggesting ABA biosynthesis is required for microbiome-
responsive suberization. The microbiome results also demonstrate typical plant-associated microbiota that
are strongly associated with sample type (e.g., root vs rhizosphere).

Continued research on plant-microbe interactions contributes to efforts in sustainable agriculture to feed a
growing global population. Increased suberin content in response to the microbiome may contribute to
further stress tolerance in soybeans, and understanding this relationship may lead to the development of
stress resistant cultivars.

[O108] GONE WITH THE WIND: CUTICULAR WAXES AS PRECURSORS OF VOLATILE ORGANIC
1,2
1,2
1,2
COMPOUNDS. Jeff Y. Chen , Aswini Kuruparan , Mahbobeh Zamani-Babgohari , and Eliana
1,2 1
Gonzales-Vigil . Department of Biological Sciences, University of Toronto - Scarborough, Scarborough,
2
ON, Canada, M1C A14; and Department of Cell and Systems Biology, University of Toronto, Toronto,
ON, Canada, M5S 3G
Correspondence to: e.gonzalesvigil@utoronto.ca

Plant surfaces are sealed by a lipidic layer known as the cuticle, which provides the first line of defence
against the environment. However, it is traditionally considered a physical barrier that provides passive
protection from biotic and abiotic stress. In Populus trichocarpa (poplar, black cottonwood tree), the
cuticle accumulates cis-9 alkenes (hydrocarbons with one double bond) on the abaxial side of expanded
leaves. Unlike other cuticle components in P. trichocarpa, alkenes show a peculiar accumulation pattern:
they increase as leaves expand and then decrease in more mature leaves, which led us to investigate the
fate of the alkenes in older leaves. A thorough examination of the lipid profiles of older leaves revealed an
increase in shorter aldehydes accompanied the decrease in alkenes. Moreover, we found that the
distribution of carbon length of the aldehydes mirrored the distribution of carbon length of the alkenes,
indicating that they were biosynthetically related. Through a series of experiments, we determined that
oxidation of cis-9 alkenes leads to two aldehydes, one of them being nonanal, an important insect
pheromone. The breakdown is a spontaneous reaction that occurs upon exposure to air and light.
Furthermore, the oxidation was also observed in other plant systems that produce alkenes, including
wheat spikes and maize silks. These results change the current paradigm that cuticular waxes are a non-
reactive barrier and bring them to the forefront as precursors of volatile molecules, notably molecules with
well-established roles in insect communication.

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