Page 187 - PC2019 Program & Proceedings

PLANT CANADA 2019

S159. A mechanical feedback loop regulates morphogenesis of pavement cell shapes in Arabidopsis
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Eng, R. ; A. Sampathkumar; R. Schneider
Max Planck Institute of Molecular Plant Physiology

Cotyledon surfaces are covered by pavement cells (PCs) with alternating lobe outgrowths and indenting
neck regions. It is postulated that cellulose microfibrils alignment mediated by microtubules (MTs)
determines the final shape of PCs by either restraining or promoting PC growth. Recent work
demonstrated that lobes form in order to reduce the biomechanical stress of the PC; however, the
relationship between MTs and biomechanical stress is unknown. Here, we demonstrate how MT ordering
and biomechanical stress leads to PC morphogenesis. Upon dissecting cotyledons from the seed and
imaging PCs for 96 hours post-dissection (hpd), we noted varying degrees of MT ordering over time. At
48 hpd, aligned MT arrays were highly correlated with necks, coinciding with peak PC growth rates and
increased lobe formation, while this correlation was reduced at necks and earlier/later timepoints. Mutants
lacking the MT-regulators, CLASP and KATANIN, had enhanced and reduced PC shape complexity,
respectively, relative to wild-type PCs. While clasp PCs had increased MT bundling at necks at all
timepoints, MT bundling at necks were absent in katanin PCs. In silico quantification of biophysical
stress revealed that mutant PCs have increased mechanical stress, suggesting that MT ordering is essential
for proper lobe formation thereby modulating mechanical stress. Taken together, we postulate a feedback
model where MT ordering regulates growth and lobe formation which subsequently feedbacks in
regulating mechanical forces and MT organization.

Ryan Eng (eng@mpimp-golm.mpg.de)

S160 Molecules in Action: Quantum dot enabled studies of plant growth regulation
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1
2
Erland, L.A.E. ; S.J. Murch ; P.K. Saxena
1 UBC
2 University of Guelph
Quantum dots (QD) are fluorescent and UV active nanoparticles which can be conjugated to diverse
molecules of interest thereby allowing for direct visualization and single molecule tracking with an
appropriate microscope. We developed a new technique to conjugate QD to plant growth regulators
(PGRs) for in vivo visualization of molecules in action. In proof of concept experiments, we used QD
conjugated indoleamines, melatonin (N-acetyl-5-methoxytryptamine) and serotonin (5-
hydroxytryptamine) and followed the movement of the PGRs in living tissues. We were able to determine
molecular location, transport patterns and redistribution in response to thermal stress in the model
medicinal plant species, Hypericum perforatum(L.). In subsequent experiments, we also conjugated QD
to other PGRs including auxins and cytokinins and visualized the action of the molecules in classic
experiments. Our experiments provide proof of concept of the applicability and utility of QD
technologies for studies of plant growth and development. In the future, studies of QD-labeled PGRs have
the potential to directly demonstrate mechanisms of action and can greatly improve our understanding of
the mechanisms, transport and localization of both traditional and emerging plant signaling molecules.

Lauren Erland (erlandl@mail.ubc.ca)

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