Page 160 - PC2019 Program & Proceedings

PLANT CANADA 2019

S105. Physiological and biochemical responses of alfalfa (Medicago sativa L.) to salt stress
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1
2
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3
Bhattarai, S. ; C. Karunakaran ; K. Tanino ; Y-B. Fu ; B. Coulman ; B. Biligetu
*1
1 University of Saskatchewan
2 Canadian Light Source
3 Agriculture and Agri-Food Canada
The objective of this study was to understand the effects of salt stress on alfalfa from the whole plant to
sub-cellular levels. Five alfalfa cultivars were grown in five gradients of salt stress of 0, 4, 8, 12 and
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16dSm electrical conductivity (EC) in a sand-based hydroponic system for 12 weeks in the greenhouse.
The elemental concentrations in leaf, stem and root tissues were determined by Inductively Coupled
Plasma-Mass Spectroscopy. Biochemical compounds in tissues of two selected alfalfa cultivars with
contrasting salinity tolerance were localized using Mid-infrared and VESPERS beamlines at Canadian
Light Source.

Increasing salt stress significantly (P<0.001) reduced plant height and dry shoot yield of alfalfa, with
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4.2% and 7.9% reduction for each 1dSm increase, respectively. Alfalfa under high salt stress
(8-16dSm ) showed high concentrations of sodium and chlorine in leaf tissues compared to stem and
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root. The in-situ study using the VESPERS showed accumulation of chlorine in the leaf lamina and leaf
margin, which resembled necrosis symptoms in salt-stressed alfalfa, while calcium accumulated in leaf
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veins. Salt tolerant alfalfa accumulated higher amides at >4dSm , which may be a key feature for its
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osmotic adjustment. We concluded that alfalfa showed ion exclusion at salinity levels of 4dSm EC, and
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shoot tissue tolerance at high salt stress (>8dSm EC) at the flowering stage. Taken together, these results
provide new insights into salt resistance mechanisms in alfalfa.
Surendra Bhattarai (surendra.bhattarai@usask.ca)

S106. The ABA-responsive SnRK1 kinase interaction network in Arabidopsis thaliana
*
Carianopol, C. ; A. Chan; S. Lumba; S. Gazzarrini
University of Toronto

Environmental stress greatly affects plants growth, posing challenges to food security. The yeast Snf1
(Sucrose non-fermenting1), mammalian AMPK (5' AMP-activated protein kinase) and plant SnRK1
(Snf1-Related Kinase1) are highly conserved heterotrimeric kinase complexes, activated under metabolic
stress to re-establish energy homeostasis in eukaryotes. In plants, the hormone abscisic acid (ABA) plays
a crucial and well-known role in stress response. Activation of SnRK1 or ABA signaling results in
overlapping transcriptional changes, suggesting these two important stress pathways share common
targets. To investigate how SnRK1 and ABA interact to regulate stress responses in Arabidopsis thaliana,
the six SnRK1 complex subunits were screened by yeast two-hybrid against 258 ABA-responsive
proteins. A set of 125 unique SnRK1-complex interactors were uncovered, which included known and
core ABA signaling components, suggesting that SnRK1 may modulate the ABA response pathway at
multiple levels. Network analysis indicates that a subset of SnRK1 kinase interactors forms a signaling
module in response to osmotic and salinity stress. Functional studies using T-DNA insertion mutants
show the involvement of SnRK1 and five interacting partners in salinity stress responses. This targeted
study uncovers the largest set of SnRK1 interactors, which can be used for further characterization of the
role of SnRK1 and its ABA-responsive partners in plant survival under stress.

Carina Carianopol (carina.carianopol@mail.utoronto.ca)

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