Page 141 - PC2019 Program & Proceedings

PLANT CANADA 2019

S67. High condensed tannin levels protect poplar against oxidative damage generated by UV-B
exposure or drought stress
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Gourlay, G. ; B. Hawkins ; J-P. Schnitzler ; I. Zimmer ; A. Albert ; P. Constabel
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1 University of Victoria; Helmholtz Zentrum
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Condensed tannins (syn. proanthocyanidins) are polyphenolic compounds synthesised from the flavonoid
pathway. Although condensed tannins are often considered to be plant defence compounds, they may
have additional biological functions. In poplar (Populus spp.), condensed tannin biosynthesis is
stimulated by multiple stresses including wounding, pathogens, UV-B, nitrogen deficiency, and high light
stress, which all generate reactive oxygen species (ROS) and oxidative stress. Tannins have high
antioxidant capacity in vitro, but whether they protect against oxidative stress in planta has not been
demonstrated. This work tests the hypothesis that condensed tannins can act as in vivo antioxidants.
Transgenic poplar saplings engineered to accumulate high concentrations of condensed tannins were
challenged with two stresses that induce accumulation of ROS - drought and UV-B exposure. Drought
stress was imposed by reducing water availability to saplings for three weeks, and UV-B treatments were
carried out in specialized environmental chambers capable of simulating sunlight including UV-B.
Chlorophyll fluorescence measurements in both the drought-stressed or UV-B stressed plants showed that
high-tannin transgenic poplar retained greater photosystem II operating efficiency (Fq’/Fm’) compared to
control plants. For both stresses, the high-tannin transgenics had lower hydrogen peroxide and
malondialdehyde levels relative to controls. Since the protective effects of condensed tannins were
observed with two distinct abiotic stresses, our data suggest that foliar condensed tannins can act as a
general defense against stress-induced oxidative damage.

Gerry Gourlay (holmgera@uvic.ca)

S68. Impact of phosphate or phosphite resupply on the proteome and phosphoproteome of
phosphate-deprived Arabidopsis thaliana suspension-cell cultures
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Ghahremani, M. ; D. Mehta ; M. Pérez-Fernández ; T. Barber-Cross ; R.G. Uhrig ; W. Plaxton
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1
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1 Queen's University; University of Albert; University Pablo de Olavide
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Despite the vital role of phosphate (Pi; HPO4 ) in growth and development, how plants signal changes in
Pi supply to adjust its uptake and utilization remains poorly understood. Pi itself has been proposed to be
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the signaling molecule that controls plant Pi starvation responses (PSRs) because phosphite (Phi; HPO3 )
is a non-metabolizable Pi analog that suppresses most aspects of the PSR. Protein phosphorylation is an
essential PTM that plays central roles in how plant cells perceive and respond to stress. Thus, the aim of
this study was to profile (phospho)proteome alterations that occur when Pi-starved (-Pi) Arabidopsis
suspension cells are resupplied with 2 mM Pi or Phi for 48 hours. LC-MS/MS of TiO2-enriched
phosphopeptides quantified a total of 3646 proteins and 1318 phosphoproteins (consisting of 5171 unique
phosphopeptides) across all conditions. Consistent with earlier reports, phosphoenolpyruvate carboxylase
was phosphorylated and more abundant in the –Pi cells, whereas several purple acid phosphatases such as
AtPAP17 and AtPAP25 were detected only in the –Pi cells. Pi or Phi resupply to the –Pi cells triggered
marked and mostly similar alterations to the total proteome and phosphoproteome, including proteins
involved in transcription, translation, proteasome function, metabolism, and signaling. t

Mina Ghahremani (m.ghahremani@queensu.ca)

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