15th International Conference on Arabidopsis Research - TAIR

T03-067
Study of root hair tip growth of Arabidopsis by videoenhanced
light microscopy
Miroslav Ovečka(1, 2), František Baluška(3, 2), Irene
Lichtscheidl(1)
1-Institute of Ecology and Conservation Biology, University of Vienna, Vienna, Austria
2-Institute of Botany, Slovak Academy of Sciences, Bratislava, Slovak Republic
3-Institute of Botany, University of Bonn, Bonn, Germany
Non-invasive methods of light microscopy are important tools in cell
biological research; they allow the study of plant morphology and structure
as well as a characterisation of the phenotype of Arabidopsis roots. We used
the technique of electronic light microscopy to analyse the morphology and
the organelle dynamics of living root hairs. This approach takes advantage
of video- and computer techniques to utilise the maximum resolution of the
light microscope or even improve it; thereby we can observe sub-resolution
particles in living cells.
With computer-assisted high-resolution light microscopy we analysed
root hairs after treatment with chemicals that monitored and modulated the
physiology and function of the plasma membrane and membrane trafficking.
It is documented with the example of structural sterols and their distribution
in the plasma membrane of root hairs. We observed changes in the rate of
tip growth, in the cytoarchitecture of the tip and in the motility of organelles
within the different developmental stages of root hairs after complexation of
sterols.
Results bring basic characteristics of the cytoarchitecture of root hair tips
of Arabidopsis thaliana essentially involved in tip growth.
This work was supported by a grant for the research trainings network TIPNET (HPRN-CT-2002-
00265) from the European Comm
T03 Cell Biology
T03-068
Role of Heat Stress Granules for mRNP Storage and
Decay
Christian Weber(1), Markus Fauth(1)
1-Department of Molecular Cellbiology, Johann-Wolfgang Goethe University, 60439-Frankfurt,
Germany
The plant heat stress response is characterized by the rapid and reversible
assembly of large cytoplasmic complexes (heat stress granules, HSG). They
serve as storage and stabilization sites of denatured proteins and contain a
considerable portion of untranslated house keeping mRNPs. The fate of these
mRNPs in the recovery period remains to be determined (reinitiation into
polysomes vs degradation). In animal cells it was shown that stress granules
induced by heat or oxidative stress contain mRNA and associated RNA binding
proteins. It was speculated that these mRNP complexes resemble defect
initiation complexes and that the mRNA binding capacity of the nuclear
hnRNP TIA-1 is essential for the formation of the granules. We will show that
the HSG complexes contain components of the translation initiation complex
like eIF4E, iso4E, 2alpha, and PABPI members. The HSG complexes are associated
with mRNP granules containing polyA-RNA and Ubp the plant homolog
of TIA-1. Whereas the interaction partners of Ubp Uba 1a and 2a stay nuclear
as well as PABPII. By in situ hybridisation we will show the cytoplasmic
behaviour of individual RNAs. However, dependent on the composition of
mRNP and the cellular situation, the mRNP in the HSG can also be destined
for decay. To address this question we cloned tagged versions of putative
mRNA decay enzymes from Arabidopsis thaliana (AtXRN4, AtDcp1, AtRrp41,
AtRrp4) and proteins that are involved in the decay pathways (AtLsm1, 2, 5,
8). Using immunofluorescence analysis, we found that AtXrn4, AtDcp1 and
AtLsm1, 2, 5 colocalize in distinct cytoplasmic foci under control conditions
and are comparable to the yeast P bodies and those structures observed
in mammalian cells. Whereas under heat stress conditions the AtDcp1 and
AtXrn4 are immediately adjacent of foci containing Hsp17-CI as indicator
of HSG complexes. In contrast Lsm proteins are localized in the HSG. We
assume that the HSG combine beside their function as storage sides for denatured
proteins also mRNP specific functions of stress granules, P-Bodies,
exosomes, and mRNP storage sides.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin