Page 284 - PC2019 Program & Proceedings

PLANT CANADA 2019

P141. A single amino-acid substitution in the Lsi1 aquaporin of tobacco confers elevated Si
transport and plasma-membrane localization
1
1
1
1
1
Coskun, D. ; R. Deshmukh ; H. Sonah ; S. Matha ; R. Frenette-Cotton ; L. Tremblay ; P. Isenring ; R.
1
1
Bélanger 2
1 Laval University
2 Université Laval
Silicon (Si) is a non-essential yet beneficial substrate to many plants, conferring heightened resilience to
environmental stress. A plant’s ability to accumulate Si is primarily dependent on the presence of a Si-
permeable Lsi1 (NIP2-1) aquaporin in its roots. Structure-function analyses of Lsi1s have thus far
revealed two key molecular determinants of Si permeability: (1) the amino-acid motif GSGR in the
aromatic/arginine selectivity filter, and (2) precisely 108 amino acids between two highly conserved NPA
domains. Curiously, tobacco (Nicotiana sylvestris) stands as a rare exception as it possesses an Lsi1
(NsLsi1) with these molecular signatures but does not accumulate Si above background levels (0.1 % leaf
dry weight), thus suggesting additional determinants of Si permeability exist. To this end, we first
observed NsLsi1 was expressed constitutively in planta. Next, Si influx was measured in NsLsi1-
expressing Xenopus oocytes and found to be very low (<13% that of OsLsi1 from rice (Oryza sativa)),
which likely explains why tobacco is a low Si accumulator. Interestingly, NsLsi1 P125F displayed a
WT
significant gain-of-function (3-fold increase in Si influx relative to NsLsi1 ), which coincided with
increased plasma-membrane localization in planta. These findings reveal a novel molecular determinant
(Phe in position 125) contributing to Lsi1 cell localization and thus Si transport in plants, and inform
breeding, biotechnological, and agricultural practices to effectively utilize this anomalous element.

Devrim Coskun (devrim.coskun.1@ulaval.ca)

P142. Towards low-input production of sub-irrigated chrysanthemums: optimizing calcium and
magnesium usage
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Duncan Stephens, S. ; E. Flaherty ; W. Sutton ; W. MacDonald ; G. Bozzo ; B. Shelp
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1
*1
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1 University of Guelph
2
Niagara College
Excessive fertilizer use in greenhouse floricultural operations results in low nutrient use efficiency by
plants, wastes nutrients, and poses significant environmental risk to water resources. Recently, we
described a nutrient delivery strategy for subirrigated, potted, disbudded chrysanthemums, wherein a
moderate level of N, S, K or P is provided during vegetative growth, in an otherwise complete nutrient
solution, while eliminating the entire nutrient suite during reproductive growth, without adversely
affecting plant yield and flower quality. Here, moderate levels of calcium (Ca) or magnesium (Mg) were
provided during vegetative growth and then replaced with deionized water at the onset of reproductive
growth. The experiments were conducted in a research greenhouse using pinched, potted plants in a split-
plot design with Ca (6.76, 3.38, and 1.69 mM) or Mg (1.5, 0.75 and 0.38 mM) treatment as the main plot
and cultivar (‘Milton Dark Pink’ and ‘Williamsburg Purple’) as the sub-plot. Market quality plants were
produced with sufficient tissue-Ca or -Mg in a diagnostic leaf, even when delivery of the corresponding
nutrient was reduced by approximately 87.5% over the crop cycle, compared to industry standards.
Bloom development was unaffected by the treatments. This research contributes to the further
development of a novel nutrient delivery strategy that reduces the rate of fertilizer application, and the
concentration/ volume of nutrient-rich solution that must be managed in accordance with applicable
environmental legislation.

Skye Duncan Stephens (sduncans@uoguelph.ca)

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