Page 220 - PC2019 Program & Proceedings

PLANT CANADA 2019

P13. Characterization of the role of SPL9 in drought stress tolerance in Medicago sativa
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1
Hanly, A. ; L. Amyot ; J. Karagiannis ; A. Hannoufa
1 University of Western Ontario
2
Agriculture and Agri-Food Canada
Climate change has caused previously ideal agricultural lands to experience events of drought resulting in
decreases to crop yield. Understanding the molecular mechanisms that underpin the response of plants to
drought stress is crucial to maximizing the efficiency of our available agricultural land through the
deployment of drought tolerant cultivars. The role of SQUAMOSA PROMOTER BINDING PROTEIN-
LIKE 9 (SPL9), a target of miR156, was studied in alfalfa’s (Medicago sativa) response to drought. SPL9
was found to affect alfalfa’s phenotype and abiotic stress response by regulating the biosynthesis of
anthocyanins. Transgenic alfalfa plants with RNAi-silenced SPL9 (SPL9-RNAi) have decreased height,
increased branching and decreased average internode length. In response to 12 days of withholding water,
SPL9-RNAi plants show increased drought tolerance and decreased leaf senescence compared to wild-
type (WT) plants. When comparing well-watered control and drought conditions, SPL9-RNAi plants
show no decreases in fresh weight of above-ground tissue that is otherwise observed in WT plants. SPL9-
RNAi plants are also better able to continue normal growth under drought stress. Significant differences
in plant growth between control and stress conditions are not seen in SPL9-RNAi plants but are observed
in WT plants. This study identifies SPL9 as a candidate molecular tool for improving alfalfa’s, and
potentially other plants’, tolerance to drought stress.

Alexandria Hanly (ahanly2@uwo.ca)

P14. Exposure to low phosphate and salinity differentiate root systems for two ecotypes of the
extremophyte crucifer Eutrema salsugineum
Irani, S.; P. Summers; E. Weretilnyk
McMaster University

Eutrema salsugineum is halophytic relative of Arabidopsis thaliana with a close phylogenic relationship
to Brassicaceae crops. We compared seedlings of two E. salsugineum ecotypes originating from the
Yukon, Canada and Shandong, China for their capacity to cope with low phosphate (Pi) and salt. Yukon
soils are typically high in salt and low in Pi, and a high tolerance to both stresses has been reported for
Yukon E. salsugineum but not for other ecotypes. In this study we compared root growth and architecture
for Yukon and Shandong seedlings growing on a gel medium containing variable combinations of Pi and
NaCl. Low Pi produced Yukon seedlings with longer main roots and lateral roots, higher root and shoot
biomass, as well as longer root hairs and higher root hair density compared to Shandong seedlings. The
addition of 100 mM NaCl to low Pi media did not alter the accession-specific features related to root
architecture. Under the low Pi treatment, elevated reactive oxygen species were detected in Shandong but
not Yukon E. salsugineum roots. Histochemical staining of roots for endogenous phosphatases showed
less activity in roots and root hairs of Yukon relative to Shandong E. salsugineum seedlings. Thus
Shandong and Yukon E. salsugineum plants are differentially tolerant to low Pi despite both ecotypes
sharing a high tolerance to salt and an extremophyte designation.

Solmaz Irani (iranis4@mcmaster.ca)

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