Page 272 - PC2019 Program & Proceedings

PLANT CANADA 2019

P117. Investigating the role of secretion in the Arabidopsis thaliana compatible pollen response
pathway
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Macgregor, S. ; D. Goring
University of Toronto

The acceptance of compatible pollen in the Brassicaceae is tightly regulated through interactions between
the pollen and the pistil. Secretion in the stigmatic papillae is proposed to be key to this interaction to
provide resources to the pollen for hydration and germination. The objective of this research is to
investigate components of the Arabidopsis thaliana secretory pathway machinery for their requirement in
the stigma for compatible pollen acceptance. Fluorescently-tagged markers that identify different
compartments in the endomembrane system are being used to gain a fuller understanding of the secretory
activity that occurs following compatible pollinations. In addition, the requirement of SNARE complex
subunits, which are implicated in vesicle fusion and cargo release, is also being investigated through loss-
of-function mutants. Our preliminary results have shown that combining SNARE knockout mutants leads
to a reduction in compatible pollen hydration, supporting their role in the compatible pollen acceptance
pathway. Higher order SNARE knockout mutants will be used in the future to further characterize the
SNARE complex’s role in compatible pollen acceptance. Together with fluorescently-tagged
endomembrane marker lines, this research will provide a better understanding of the stigmatic papilla’s
secretory system, and how this system is employed in the acceptance of compatible pollen.

Stuart Macgregor (s.macgregor@mail.utoronto.ca)

P118. POPCORN modulates auxin flow and polarity to define adaxial-abaxial cell fate in
Arabidopsis leaf development
Quilichini, T.; P. Gao; R. Datla; D. Xiang
National Research Council Canada

Co-ordinated developmental programs produce flat and symmetrical leaves to perform broad biological
functions including efficient light capture, gas exchange and photosynthesis in plants. Arabidopsis leaves
exhibit symmetry in three axes, across proximal-distal (base to tip), medial-lateral (mid-vein to edge), and
adaxial-abaxial (upper to lower) planes. Among these, symmetry in the adaxial-abaxial plane is critical
for precise cell and tissue specification and their organization within the leaf. The specification and
maintenance of this important bilateral symmetry is regulated by a network of genes functioning within
domains of the shoot apical meristem and the lateral organ primordia that produce leaves. Here, we
demonstrate that POPCORN (PCN), a WD-40 protein required for shoot apical meristem functions, plays
critical roles in coordinating regulatory networks of leaf development in Arabidopsis. Insights into these
roles are based on our findings that loss of function pcn mutants exhibited abnormal leaf development
with phenotypic defects that were further enhanced with mutations in adaxial- or abaxial-promoting
genes, producing sterile, stunted plants with severe leaf defects including radialized leaves. The network
of these genes and potential regulators downstream of PCN was examined through integrated analyses
including RNA-seq, microRNAseq and pull-down assays along with developmental and cell biological
focused analyses of vascular development, leaf venation, and auxin signaling. These studies revealed
PCN as a key regulator of adaxial-abaxial polarity establishment and leaf development in Arabidopsis.

Teagen Quilichini (teagenquilichini@gmail.com)

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