Book of Abstracts - Geyseco

P - Posters
activated by phosphorylation of its penultimate residue, a threonine
and the consecutive binding of regulatory 14-3-3 proteins to
the enzyme C-ter. Mass spectrometry analysis of purified PMA2
(Plasma membrane H+-ATPases from N. plumbaginifolia) led to
the identification of new phosphorylation sites. Phosphorylated
Ser938 and Thr931, both located in the PMA2 14-3-3 binding
site, were shown to act as negative regulators of the 14-3-3 binding
and hence the enzyme activation whereas phosphorylated
PMA2 Thr889, also located in the enzyme C-ter but outside the
14-3-3 binding site, seemed to be involved in an activation mechanism
independent of the 14-3-3 protein binding. Altogether 4
phosphorylated sites concur to a complex regulation of the H+-
ATPase. To identify the kinases involved, proteins co-purified
with a His-tagged PMA2 isoform expressed in tobacco BY2
suspension cells were analyzed by mass spectrometry. Some
putative kinases have been identified. To better characterize the
physiological roles of the H+-ATPase in the plant, an activated
enzyme was expressed in tobacco and Arabidopsis. Transgenic
plants had a pleiotropic phenotype with, for example, a modified
development and a better resistance to salt stress and basic pH.
P11-018: PATTERN FORMATION DURING SOMATIC
EMBRYOGENESIS IN SCOTS PINE
Abrahamsson, M.* - Valladares, S. - von Arnold, S.
Swedish University of Agricultural Sciences, Department of
Plant Biology and Forest Genetics
*Corresponding author, e-mail: malin.abrahamsson@vbsg.slu.se
Somatic embryogenesis is an attractive method to propagate conifers
vegetatively. However, in order to efficiently regulate the
formation of plants via somatic embryos it is important to understand
how the somatic embryos develop. The aim of this study
has been both to elucidate the development of somatic embryos
in Scots pine and to identify deviations from the normal plan
leading to developmental arrest or to progressive accumulation
of errors resulting in aberrant cotyledonary embryos. We have
compared the developmental pathway of somatic embryogenesis
in representative cell lines yielding cotyledonary embryos with
normal and abnormal morphology. Embryogenic cultures of
Scots pine are initiated from immature embryos during the cleavage
phase, and proliferation by cleavage can also be observed
in embryogenic cultures. In all cell lines a large proportion of
the developing embryos degenerate but the degeneration pattern
differs among cell lines. However, there were no fundamental
differences in the early patterning of embryos between the cell
lines except that the early somatic embryos in cell lines giving
rise to abnormal embryos carried supernumerary suspensor cells,
resulting in an unbalanced ratio between the embryonal mass and
the suspensor, which partly can be explained by an aberrant polar
auxin transport.
P11-019: ISOLATION AND CHARACTERIZATION OF
ENDOSOMAL COMPARTMENTS IN ARABIDOPSIS
Sancho Andrés, G.* - Groen, A.J. - Lilley, K.S. - Aniento, F.
Universidad de Valencia
*Corresponding author, e-mail: gloria.sancho@uv.es
The plasma membrane (PM) of plant cells undergoes dynamic
changes in protein composition. Several PM proteins have
been shown to cycle between the PM and endomembrane
compartment(s), whereas other PM proteins are internalised and
targeted to the vacuole for degradation. PM protein dynamics
thus determines cell behaviour and affects plant performance.
However, our current knowledge of the underlying mechanisms
of these processes in plants is virtually non-existent. In animals,
early/sorting endosomes are important sites for receptor signaling.
Although this may also apply to plants, there are no markers
to distinguish plant early/sorting from recycling endosomes. The
endosomal compartments in which plant PM proteins are sorted
for degradation or recycling to the PM are morphologically and
functionally not defined, and their composition in terms of resident
and cargo proteins is essentially unknown. In this work, we
have carried out two proteomics methods to characterise endosomal
compartments in Arabidopsis. Firstlyw, e have combined
subcellular fractionation with LOPIT (Localization of Organelle
Proteins by Isotope Tagging), a method which allows assignment
of proteins to organelles using high throughput quantitative
proteomics approaches. Secondly, in parallel, we have performed
immunoisolation experiments, using as antigen the human
transferrin receptor (hTfR), a model receptor for endocytosis in
animal cells, heterologously expressed in transgenic Arabidopsis
plants.
P11-020: NOVEL INSIGHTS INTO AQUAPORIN TRA-
FFICKING TO THE PLASMA MEMBRANE
Besserer, A. - Bienert Gerd, P. - Chevalier, A. - Zelazny, E. -
Chaumont, F.
Institut des sciences de la vie, Université catholique de Louvain
The movement of water across plant plasma membrane (PM) depends
on the amount and activity of aquaporins belonging to the
Plasma membrane Intrinsic Proteins (PIP) subfamily. Recently,
we showed that maize aquaporins belonging to PIP1 and PIP2
groups form hetero-oligomers when co-expressed in leaf mesophyll
protoplasts. This physical interaction regulates their trafficking
and triggers relocalization of ZmPIP1 from the endoplasmic
reticulum (ER) to the PM (Zelazny et al., 2007;2009). This result
suggests that ZmPIP1s carry ER retention signals which are
inefficient upon hetero-oligomerization. Expression of mutated
and chimeric PIPs indicates that the loop A of ZmPIP1;2 may
contain an ER retention signal as its replacement with ZmPIP2,5
loop A leads to some extent to ZmPIP1;2 trafficking to the PM,
but only if an additional ER export motif (N-terminal diacidic
acid motif) is present. Regulation of PIP trafficking to the PM
was further characterized in maize protoplast and in tobacco
epidermal cells by co-expressing ZmPIP2;5 and the dominant
negative mutant syntaxin SYP121-sp2. Our results showed that
ZmPIP2;5 traffic to the PM is hampered by SYP121-sp2. Putative
interaction between SYP121 and ZmPIP2;5 is under investigation.
The membrane osmotic water permeability decreased in
cells co-expressing ZmPIP2;5 and SYP121-sp2. Altogether data
point toward a complex and highly integrated regulation of PIP
trafficking in the maintenance of cellular water homeostasis.
P11-021: COMPARISION OF GALACTOGLUCOMAN-
NAN OLIGOSACCHARIDES ACTION ON CELL ELON-
GATION IN HYPOCOTYL AND PRIMARY ROOT
Richterová, D.* - Kollárová, K. - Lišková, D.
Institute of Chemistry, Slovak Academy of Sciences
*Corresponding author, e-mail: danica.richterova@savba.sk
Galactoglucomannan oligosaccharides (GGMOs) inhibit the
auxins-induced elongation growth of stem segments and this
effect is dependent on their chemical structure and concentration.
GGMOs influenced induction and elongation of adventitious and
lateral roots. The aim of this work was to answer the question: is
the effect of GGMOs in elongating hypocotyls and roots related
with the elongation or division of cells, and in which tissues?
GGMOs were derived from spruce galactoglucomannan. Modified
GGMOs - GGMOs-g were prepared by treatment of GGMOs
with purified α-galactosidase. Uniform seedings of mung
bean (Vigna radiata (L.) Wilczek) were transferred to hydroponic
Hoagland solution containing GGMOs or GGMOs-g alone and/
or in combination with IBA. Plants were grown 7 days in controlled
conditions and then the length of hypocotyl and primary root
was measured. For light microscopy the whole-mount procedure
was used and the samples were stained with toluidine blue. The
length of cells was determined by Lucia analysis system. The
data were analyzed using ANOVA. GGMOs alone or in combination
with IBA inhibited hypocotyl elongation, but they stimu-
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