Cellular-level mechanisms of polarity and their role in plant growth

Abley, Katie (2014) Cellular-level mechanisms of polarity and their role in plant growth. Doctoral thesis, University of East Anglia.

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Abstract

Coordinated cell polarity fields are essential for plant and animal development. Several models
have been proposed for how these cell polarity fields are established. However, it remains unclear
how different models are related to each other and how coordinated cell polarity fields are
generated. Here, I present a hypothesis that both plant and animal cell polarity fields are based
on a common intracellular partitioning (IP) mechanism that spontaneously generates cell polarity
independently from pre-established asymmetries. I show how plant polarity fields may be
accounted for through an auxin-mediated indirect cell-cell coupling mechanism that coordinates
polarities established by IP, and provides an explicit molecular hypothesis that is consistent with
current experimental data. I show that this model behaves similarly to a flux-based model of plant
polarity in several scenarios, and that these models make testable predictions that differ from
those of published up-the-gradient models. To test the different plant models, I use
kanadi1kanadi2 (kan1kan2) mutant Arabidopsis leaves, which develop ectopic outgrowths, as a
simple system to study the dynamics of polarity reorientations. I compare contrasting model
predictions with observed polarity changes and patterns of auxin-related gene expression
preceding the development of ectopic outgrowths. Together with an analysis of wild-type leaves,
this reveals that indirect cell-cell coupling and flux-based models are more compatible than the
up-the-gradient model with patterns of auxin biosynthesis and import in leaves. I next show that
the CUC2 transcription factor is essential for kan1kan2 outgrowth development. Through
modelling and experiments, I show that CUC2-regulation of auxin biosynthesis most-likely plays an
important role in polarity reorientations. Finally, I present models for how epidermal and subepidermal
PIN polarity patterns may be coordinated and lead to changes in growth. This work
reveals the value of comparing different computational models with experimental data when
investigating mechanisms of polarity generation.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Brian Watkins
Date Deposited: 18 Feb 2015 16:46
Last Modified: 18 Feb 2015 16:46
URI: https://ueaeprints.uea.ac.uk/id/eprint/52341
DOI:

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