Book of Abstracts - Geyseco

FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology
1
Institut de Recherche en Biologie Végétale - Université de Montréal
2
Ecole Polytechnique de Montréal
*Corresponding author, e-mail: youssef.chebli@yahoo.ca
Cellular growth in plant cells is driven by the turgor pressure but
controlled by the mechanical properties of the cell wall. The formation
of a cellular protuberance requires the spatially confined
yielding of the wall. Using finite element modeling, a technique
used in engineering, we established a theoretical model of tip
growth as it occurs in pollen tubes and root hairs.
The model predicts that a characteristic spatial distribution of
mechanical properties in the cell wall is required to produce the
self-similar growth pattern that characterizes these cell types.
The mechanical profile is characterized by a steep increase in cell
wall extensibility in the transition zone between dome-shaped
apex and cylindrical region of the cell.
To compare the theoretical requirements with the biological
reality, we quantitatively assessed the spatial distribution of various
cell wall components in the pollen tube wall of Lilium and
Arabidopsis. We used immunofluorescence methods combined
with quantitative image analysis to locate pectin, cellulose and
callose. We found remarkable agreement between the expected
gradient in cell wall extensibility and the distribution of de-esterified
pectin polymers. Furthermore, we identified the orientation
of cellulose microfibrils using scanning electron microscopy and
found that their mechanical support is particularly important in
the transition region. Callose on the other hand provides mechanical
support to the cylindrical shank of the cell. Our data show
that tip growth is produced by a highly controlled interplay of
cell wall assembly processes and that each component is important
for different aspects governing the shape and growth dynamics
of the elongating cell.
P11-014: KUNITZ TRYPSIN INHIBITOR AS A PLANT
CELL DEATH MODULATOR
Komarova, T.* - Sheval, E. - Dorokhov, Y.
Moscow State University, A.N.Belozersky Institute
*Corresponding author, e-mail: t.v.komarova@gmail.com
Normally plant cell is adapted for producing large amounts of
protein which is targeted and stored in special cellular compartments.
But intensive uncontrolled and untargeted protein
production is likely to result in programmed cell death (PCD). To
study cell death of protein overexpressing plant cell we created
specific vector system, TMV:GFP, allowing GFP production in
huge amounts and resulted in cells death 3 days after agroinjection.
Using microscopy and biochemical approaches we described
the following features of the process: stages of cell and tissue
death; GFP behavior in aggregates and its proper folding. Moreover
we analyzed the pattern of mRNA expression in Nicotiana
benthamiana tissues just before their death using subtractive hybridization.
Several candidate genes including specific biotic cell
death-associated protein (CDM) were found to be upregulated.
NbCDM appeared to have strong homology with Kunitz trypsin
inhibitors (KTI) family which is specific for serine proteases
been implicated in PCD in plants. Joint expression of NbCDM
under control of 35S promoter (35S-NbCDM) with TMV:GFP
resulted in enhanced lesion development whereas 35S-NbCDM
per se didn’t induce necrotisation. Upregulation of NbCDM expression
was also registered as a response to virulent bacterial pathogen
Ralstonia solanacearum or even after its NLS-containing
protein overexpression. Asit is well known that PCD requires a
coordinate activation of different factors such as proteases and
suppressors, NbCDM is likely to be one of such players inhibiting
and modulating these processes.
P11-015: GENERATION OF NITRIC OXIDE UNDER
ANOXIA IS INDEPENDENT OF NITRATE REDUCTASE
ACTIVITY.
Kingston-Smith, A.* - Eelen, I. - Davies, T.E. - Mur, L.A.J. -
Aberystwyth University
*Corresponding author, e-mail: ahk@aber.ac.uk
Exposure of plants to abiotic stress causes changes in foliar protein
which can affect crop yield and quality. This is also true of
plant parts ingested by grazing ruminants whereby leaf cells are
exposed to multiple stresses (heat, anoxia, microbial attack) in
the hours following rumen entry causing autolysis. This has implications
for the poor use of feed N by ruminants, which results
in N deposition on land (as animal wastes) and contributes to
N2O generation. As the cell signal NO has been implicated in
cell death under biotic and abiotic stress this work investigated
its potential role in control of autolysis in ingested plant cells.
NO was detected in Arabidopsis thaliana Col-0 leaf discs after
in vitro exposure to rumen-stress conditions. The source of NO
generation in plants is currently unknown but could occur enzymically
(catalysed by nitrate reductase; NR) or non-enzymically,
an is enabled by an increase in intracellular nitrite under low oxygen
conditions. The role of NR in NO generation under anoxia
was determined by exposure of leaf discs from Col-0 and mutants
Nia 1, Nia 2 and AtNos (which had 56%, 5% and 100%
of NR activity of Col-0) to rumen-like conditions. NO was detectable
by fluorescence microscopy in all lines after 1h. These
results, plus no significant differences in foliar nitrite suggest that
non-enzymic NO production in ingested plant cells could be responsible
for autolysis.
P11-016: ASYNCHRONOUS DEATH OF STOMATA
GUARD CELLS PREDETERMINED BY THE ASYMME-
TRIC OPEN MITOSIS
Selga, T.* - Maija, S.
Faculty of Biology, University of Latvia
*Corresponding author, e-mail: turs.selga@lu.lv
The control of programmed cell death (PCD) by previous asymmetric
cell division (ACD) in plants is far from clear. The stomatal
cell lineage is a typical example of precisely planned series
of ACDs, that finish with as if symmetrical division of the guard
mother cell (GMC) to form identical stomatal guard cells (GC)
(Hove and Heidstua 2008, Nodeau 2009, Dong et al 2009) We
searched among several hundreds of stomata in various stages
of their development and senescence from the young, full grown
and senescing leaves of tobacco (Nicotiana tabacum L.) by use
of several methods and techniques of cyochemistry and microscopy.
Our data suggests that the stomatal GMCs in reality always
divide spatially asymmetrically by the classic open mitosis and
develop unequal GCs, that age and die differently by different
alterations of their nuclei and other organelles. Perinuclear endoplasmic
reticulum in one of sister cells disappears faster than
in another. The GMCs and GCs always are structurally joined at
least with one nucleus of adjacent cell and migration of variously
stained nuclear substance among them is evident. The permanent
plastid-nuclear complex (PNCs) that we have repeatedly
demonstrated in photosynthesizing cells of different vascular
plants exists in all GMCs and GCs during all their lifespan, and
evidently are important control units.
P11-017: IDENTIFICATION OF PHOSPHORYLATED
RESIDUES IN THE H+-ATPASE AND PHYSIOLOGICAL
CONSEQUENCES OF THE EXPRESSION OF AN ACTI-
VATED FORM IN THE PLANT
Duby, G.* - Piette, A.S. - Piotrowiak, D. - Salladini, A. - Boutry, M.
Institut des Sciences de la Vie, Université Catholique de Louvain
*Corresponding author, e-mail: geoffrey.duby@uclouvain.be
The plasma membrane H+-ATPase is building a proton electrochemical
gradient that activates secondary transporters. It is involved,
in cytosolic pH regulation, cell elongation and stomata
aperture. It contains an auto-inhibitory C-terminal region and is