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Abstract Detail


Genome, Phenome, Environment, and Evolution of Land Plants

Perroud, Pierre-François [1], Quatrano, Ralph S. [2], Cove, David J. [1].

Cell polarity in the protonemata of Physcomitrella patens.

Starting from a single cell, a spore, moss protonemal growth depends on polar growth to form the cell mat that will give rise to the three dimensional gametophore. During this developmental phase, the tip cell shows two distinct polarity processes. First, tip cells divide in a highly polar manner, to give two very different cells, a new tip cell similar to the initial one and a basal cell that stops tip growth, but retains the potential for asymmetric cell division. Secondly, tip cell elongation itself is highly polarized. Cell extension occurs only near the tip, where new cellular components are constantly added to sustain growth. Additionally, the tip cell has the capacity to respond to environmental clues, including gravity and light, redirecting growth polarity accordingly.
We are approaching the cellular dissection of these polarity processes by two different ways. First, as efficient gene targeting in Physcomitrella patens allow us to use a reverse genetic approach, we focused on candidate genes potentially implicated in cell polarity. We deleted genes coding for two protein members the Arp2/3 and WAVE/Scar complexes respectively, known to be involved in actin filament organization. The resulting phenotypes clearly demonstrate their involvement in polar cell elongation, without affecting cell division polarity or the ability to respond to light clues. We are continuing this approach, focusing our investigation on a new set of proteins found to be associated with the WAVE/Scar complex, HSP70s. Secondly, we are using a forward genetic approach to find new gene involved in polar growth. Using ion beam irradiation on spores, we are establishing a Physcomitrella patens deletion library. This mutant collection is systematically screened for morphological phenotypes in protonemal development as well as alterations in the response to gravity and light.


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1 - Washington University in St. Louis, Biology, One Brookings Drive, Campus Box 1137, St Louis, MO, 63130, USA
2 - Washington University in St. Louis, Department of Biology, One Brookings Drive, Campus Box 1137, St. Louis, MO, 63130-4899, USA

Keywords:
Physcomitrella patens
protonema
tip growth
cell polarity
actin cytoskeleton.

Presentation Type: Symposium or Colloquium Presentation
Session: SY4
Location: Ballroom 2/Cliff Lodge - Level B
Date: Monday, July 27th, 2009
Time: 3:15 PM
Number: SY4005
Abstract ID:646


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