Page 136 - Plant Canada 2024 Proceeding

PLANT CANADA 2024

PROTEIN (CLASP). CLASP expression is altered by both BZR1 activity and light availability, thereby fine-
tuning cell proliferation in response to environmental conditions through modulation of microtubule
dynamics. In addition, CLASP also modulates meristem activity through an interaction with SORTING
NEXIN 1 (SNX1) which sustains the auxin transporter PIN2, a known target of TOR, at the plasma
membrane. I propose that CLASP acts as a crucial component of the TOR signaling pathway, providing a
mechanism by which sugar affects root meristem activity and growth. My research shows CLASP null
mutant plants display reduced sensitivity to pharmacological inhibition of TOR at the organ, cellular and
subcellular levels. Plants lacking functional CLASP fail to increase cell proliferation in response to sugar,
suggesting it is required for this process. Both PIN2 expression and auxin distribution are unaltered by
TOR inhibition in the absence of CLASP. This effect is mediated by the brassinosteroid signalling
pathway, as both constitutively active BZR1 and mutation of the BZR1 binding site within the CLASP
promoter prevents TOR dependant changes in root growth and CLASP expression. Through
characterization of the interaction between CLASP, TOR and plant hormones, this work provides insight
on how the sugar provision is translated into altered root development, thereby furthering our
understanding of how plants perceive their changing environment.

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[O69] HOW INTERNAL GROWTH CONTROLS PLANT MORPHOGENESIS? Sylvia R. Silveira , Loann
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3
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Collet , Sahil M. Haque , Luc Lapierre , Agnieszka Bagniewska-Zadworna , Frederick P. Gosselin ,
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1 1
Richard S. Smith , Anne-Lise Routier-Kierzkowska , and Daniel Kierzkowski . Institut de Recherche en
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Biologie Végétale, Département de Sciences Biologiques, Université de Montréal, 4101 Sherbrooke St E,
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Montréal, QC, H1X 2B2, Canada; Department of General Botany, Institute of Experimental Biology,
Faculty of Biology, Adam Mickiewicz University, Uniwersytetu Poznańskiego 6, 61-614 Poznań, Poland;
3 Laboratory of Multiscale Mechanics (LM2), Department of Mechanical Engineering, Polytechnique
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Montréal, Montréal, QC H3C 3A7, Canada; and Department of Computational and Systems Biology,
John Innes Centre, Norwich NR4 7UH, UK
Correspondence to: sylvia.rodrigues.da.silveira@umontreal.ca

The differential growth between connected plant tissues generates mechanical conflicts which are
thought to regulate organogenesis. The roles of outer and inner layers in this process remains a matter of
debate. Using the anther as a model system we explore how mechanical interactions control the
acquisition of complex three-dimensional organ shapes. By combining live-cell imaging, 3D growth
analysis, osmotic treatment, genetics, and mechanical modeling, we demonstrate that lobe outgrowth is
driven by a fast localized growth in internal cells. Additionally, we show that at later stages, the
mechanical load shifts to the endothecium, contributing to the proper shaping of the anther. Our findings
reveal how mechanical interactions between tissue layers control 3D morphogenesis.

[O70] A UNIVERSAL MODEL OF EMBRYO DEVELOPMENT IN LAND PLANTS (EMBRYOPHYTES)
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AND THEIR POTENTIAL APPLICATIONS FOR CROP IMPROVEMENT. Prakash Venglat , Perumal
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Vijayan , Timothy F. Sharbel , Abidur Rahman , and Karen Tanino . College of Agriculture and
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Bioresources, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; and Department of Plant
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Biosciences, Faculty of Agriculture, Iwate University, Morioka, Iwate 0208550, Japan
Correspondence to: prakash.venglat@usask.ca; karen.tanino@usask.ca

The evolution of land plants (embryophytes) is marked by a series of adaptations enabling their
colonization of diverse terrestrial habitats. This involved a stepwise evolution of the embryonic program,
allowing for successful reproduction and dispersal in challenging environments. Similarly, the root
program in early embryophytes underwent progressive development, facilitating nutrient acquisition and
anchorage. A key aspect of plant adaptation is their regenerative capacity, a trait deeply integrated into
plant development and asexual propagation throughout evolution. The traditional model of embryo
development, centered on a bipolar apical-basal axis, as observed in Arabidopsis, may not fully
encompass the diversity of mechanisms across land plants. An alternative evolutionary model, taking into
account the stepwise evolution of embryogenesis, root development, and regenerative capacity, to be
discussed in this presentation, offers a more comprehensive understanding of plant embryo development.
This proposed universal model of embryo development in land plants would provide a valuable framework
for studying various species, revealing commonalities and unique adaptations. Such knowledge could be
harnessed for crop improvement by manipulating key developmental pathways to enhance traits like root
development, nutrient use efficiency, and yield potential. Understanding the regenerative capacity

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