Book of Abstracts - Geyseco
Book of Abstracts - Geyseco
Book of Abstracts - Geyseco
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P - Posters<br />
tructural rearrangements in cell organelles during adaptation to<br />
temperature stresses are discussed.<br />
P11-026: VESICLE DELIVERY IN POLLEN TUBES: PER-<br />
FECTLY COORDINATED INTRACELLULAR LOGIS-<br />
TICS<br />
Van Oostende, C. 1 *- Guillet, D. 2 - Juillot, S. 1 - Geitmann, A. 1<br />
1<br />
Institut de recherche en biologie végétale-Universite de Montreal<br />
2<br />
Mc Gill University<br />
*Corresponding author, e-mail: chloevanoostende@gmail.com<br />
Cellular growth in plants implies the continuous assembly <strong>of</strong> new<br />
cell wall surface to prevent the expanding wall from rupturing.<br />
Most plant cells are characterized by diffuse growth that requires<br />
cell wall assembly over large surfaces. In contrast, the generation<br />
<strong>of</strong> complex cell shapes necessitates spatially confined growth and<br />
assembly processes. An example for this is the pollen tube, which<br />
displays tip-growth, where the expansion occurs solely at the extreme<br />
end <strong>of</strong> the cell. Pollen tube growth plays a crucial function<br />
during sexual plant reproduction since it ensures the delivery <strong>of</strong><br />
the male gametes to the ovules which are nestled deep in the<br />
pistillar tissues <strong>of</strong> the receiving flower.<br />
Pollen tube growth is extremely fast and, therefore, cell wall assembly<br />
is the principal metabolic activity. The spatial confinement<br />
<strong>of</strong> the cell wall assembly requires an intracellular transport<br />
system that is precisely controlled in space and time. Hence, trafficking<br />
<strong>of</strong> vesicles and other elements <strong>of</strong> the endomembrane system<br />
(Golgi, endoplasmic reticulum, endosomes) must be subject<br />
to a sophisticated system <strong>of</strong> cellular transport logistics mediated<br />
by the cytoskeleton. By combining high temporal and spatial resolution<br />
laser scanning microscopy with advanced imaging techniques<br />
originally developed for molecular movements (STICS,<br />
spatio-temporal image correlation spectroscopy), we monitored<br />
the delivery <strong>of</strong> vesicles towards the tube apex, the movements <strong>of</strong><br />
organelles and the dynamics <strong>of</strong> the cytoskeleton. We used these<br />
motion pr<strong>of</strong>iles to generate a mathematical model <strong>of</strong> intracellular<br />
trafficking that will help us to understand the logistic transport<br />
principles employed by growing plant cells.<br />
P11-027: GENERATION OF ACETOLACTATE SYNTHA-<br />
SE INHIBITORS - TOLERANT ALFALFA<br />
Feuillebois, P 1 * - Schaller, A. 2 - Hain, R. 1<br />
1<br />
Bayer CropScience, Herbicide Research<br />
2<br />
University <strong>of</strong> Hohenheim, Institute <strong>of</strong> Plant Physiology and Biotechnology<br />
*Corresponding author, e-mail: pauline.feuillebois@bayercropscience.com<br />
The cultivated alfalfa, Medicago sativa, is one <strong>of</strong> the most valuable<br />
legumes in the world. It is a perennial dicot with a tetraploid<br />
genome, rich in proteins, minerals and vitamins. Alfalfa is thus<br />
widely grown as forage for cattle. Chemical weed control is <strong>of</strong>ten<br />
necessary at an early stage since weeds in alfalfa fields reduce<br />
the yield and the crop quality. To enable better weed control in<br />
alfalfa, improving crop and seed production quality, our project<br />
aims to generate Acetolactate Synthase Inhibitors (ALSi) tolerant<br />
alfalfa using both GMO and non-GMO approaches. An in vitro<br />
alfalfa tissue culture has been set up by screening RA3 individuals<br />
(Medicago sativa L., cv Regen S, clone RA3) for their embryogenic<br />
response. Conditions have been optimized allowing<br />
regeneration cycles <strong>of</strong> fifty days on average. As the Acetolactate<br />
Synthase (ALS) enzyme is the target <strong>of</strong> ALSi herbicides, two<br />
ALS genes (MEDSA_ALSa and MEDSA_ALSb) have been<br />
identified in Medicago sativa and their sequences have been<br />
obtained. In the non-GMO approach, chemical mutagenesis is<br />
performed on somatic embryos to obtain putative ALSi tolerant<br />
mutants, screened using sulfonylurea herbicides (SUs). For the<br />
GMO approach, Agrobacterium tumefaciens - mediated alfalfa<br />
leaf disc transformations are carried out using an Arabidopsis<br />
thaliana mutated ALS gene conferring ALSi tolerance fused to a<br />
transit peptide. Somatic embryos obtained are selected with SUs<br />
to evaluate the potential herbicide tolerance. Positive tolerant<br />
plants will be tested for SUs tolerance in the greenhouse and fully<br />
characterized using molecular biology methods.<br />
P11-028: MECHANISTIC FRAMEWORK FOR POLAR<br />
PIN AUXIN EFFLUX CARRIER TARGETING IN PLANT<br />
CELLS<br />
Kleine-Vehn, J.* - Jiri Friml<br />
VIB - Gent university<br />
*Corresponding author, e-mail: jukle@psb.ugent.be<br />
Cell polarity is indispensable for differentiation, proliferation<br />
and morphogenesis <strong>of</strong> unicellular and multicellular organism.<br />
Most <strong>of</strong> our knowledge is derived from animal epithelial cells<br />
that organize cell polarity via the formation <strong>of</strong> tight junctions<br />
that separate distinct plasma membrane domains. Polarized plant<br />
cells lack tight junctions and the underlying mechanism that ensures<br />
cell polarity in plants is largely unknown.<br />
PIN proteins are prominent polar cargos that determine the direction<br />
and rate <strong>of</strong> the cellular export <strong>of</strong> the phytohormone auxin.<br />
Here we provide molecular and mechanistic insights into polar<br />
PIN targeting. Quantitative life-cell imaging techniques revealed<br />
that plant cells facilitate spatially defined exo- and endocytosis by<br />
regulated endosomal trafficking and subsequent short range vesicle<br />
transport. These endosome-based mechanisms enable superpolar<br />
exocytosis to an inner core in the apical plasma membrane<br />
domain and the retrieval <strong>of</strong> non-polar PIN proteins by spatially<br />
defined endocytosis via a clathrin-dependent mechanism at the<br />
apical-lateral cell junction (adjacent to the polar domain). This<br />
interweaving mechanism for PIN polarity maintenance gets further<br />
stabilized by a sterol-dependent clustering <strong>of</strong> PIN proteins in<br />
the plasma membrane, largely abolishing their lateral diffusion.<br />
Our findings provide the first mechanistic insight <strong>of</strong> how nonepithelial<br />
cells, such as plant cells, maintain polar plasma membrane<br />
domains.<br />
P11-029: REQUIREMENTS FOR NUCLEAR AND NU-<br />
CLEOLAR LOCALIZATION OF ARABIDOPSIS RIBO-<br />
SOMAL PROTEIN L23A<br />
Bonham-Smith, P.* - Savada, R.P.<br />
University <strong>of</strong> Saskatchewan<br />
*Corresponding author, e-mail: peta.bonhams@usask.ca<br />
The mechanism underlying the transport <strong>of</strong> plant r-proteins from<br />
the cytoplasm into, and their retention in, the nucleus/nucleolus<br />
is not understood. R-protein L23a is one <strong>of</strong> 81 r-proteins in Arabidopsis.<br />
It is present in two is<strong>of</strong>orms; L23aA that is essential for<br />
plant development under normal conditions and L23aB is not.<br />
Both is<strong>of</strong>orms have nine putative Nuclear Localisation Sites. Site<br />
Directed Mutagenesis <strong>of</strong> any one NLS has no effect on nuclear/<br />
nucleolar localization <strong>of</strong> L23aA. Simultaneous mutation <strong>of</strong> all<br />
nine NLSs has no effect on nuclear localization, however, nucleolar<br />
localization is completely disrupted. Combinatorial mutation<br />
studies show that, five (10KKAD13, 17KALK20, 86KK87,<br />
121KK122, and 133KK134) NLSs are required for nucleolar<br />
localization. We are currently investigating: i) if nuclear localization<br />
<strong>of</strong> L23aA is mediated by the classic importin pathway and<br />
ii) what differentiates movement into and retention <strong>of</strong> L23aA in<br />
the nucleolus (rRNA binding) from nuclear localisation.<br />
P11-030: THE ROLE OF REVERSIBLE ZEATIN GLU-<br />
COSYLATION IN THE HOMEOSTASIS OF CYTOKI-<br />
NINS<br />
Kiran, N. S.* - Dubova, J. - Brzobohaty, B. -<br />
*Corresponding author, e-mail: kiran@mendelu.cz<br />
Reversible glucosylation <strong>of</strong> zeatin-type cytokinins is important<br />
for the homeostasis <strong>of</strong> active cytokinin forms at certain developmental<br />
stages. The sub-cellular location <strong>of</strong> this conversion<br />
P