15th International Conference on Arabidopsis Research - TAIR

T04-061
LOW-LIGHT- AND ETHYLENE-INDUCED HYPONASTIC
GROWTH IN ARABIDOPSIS THALIANA
F.F Millenaar(1), M. Cox(1), L.A.C.J Voesenek(1), A.J.M. Peeters(1)
1-Utrecht University, Plant Ecophysiology, The Nederlands
Hyponastic growth is upward bending of leaves in response to low-light, a
low red/far-red light ratio and ethylene. Using a computer controlled digital
camera setup the kinetics of hyponastic growth is measured in great detail.
Natural accessions of Arabidopsis thaliana (Be0, Col, Cvi, Kas, Ler, Nd, Rld,
Shah and Ws) showed considerable genetic variation in hyponastic growth
upon exposure to ethylene (Col strongest, Ler no effect) and low light (both
Col and Ler show effect). In order to unravel the signal transduction chain,
mutants in the ethylene and light perception were exposed to 5ppm ethylene
and/or low-light (LL). Ethylene signal transduction mutants, which not responded
to ethylene, did show hyponastic growth after transfer to low-light. Also
some light perception mutants that did not respond to LL, showed hyponastic
growth upon ethylene exposure. Therefore, we concluded that ethylene-
and LL-induced hyponastic growth are regulated by, at least partly, parallel
operating pathways. Since differential growth often is associated with auxin,
mutants in auxin ubiquitination, transport and transcription were studied
during ethylene addition and/or LL. All these mutants are characterized by
a wild-type hyponastic growth, only a few auxin transport or transcription
mutants did not respond to LL and ethylene. Micro-array analysis did not
show an up-regulation of ethylene responsive genes in LL.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T04-062
Functional analysis and subcellular localization of
STO in planta
Martin Indorf(1), Ralf Markus(1), Gunther Neuhaus(1), Marta Rodriguez-Franco(1)
1-Universität Freiburg, Institut für Biologie II/Zellbiologie, Schänzlestr.1, D-79104 Freiburg,
Germany
Calcium is involved in the response of plants and microorganisms to various
stimuli, among them salt stress. We developed a yeast complementation
system using a knock out mutant of the CCH1 gene of Saccharomyces
cerevisiae that encodes a putative calcium channel. This KO strain is growth
sensitive to high salt concentrations. Complementation analysis of the cch1
mutant with an A. thaliana cDNA library resulted in the isolation of 16 clones
that could rescue the salt sensitive growth phenotype of the mutant. One
of this clones contained the cDNA of STO, a gene that previously has been
shown to complement other salt defective growth yeast mutants (Lippuner et
al., 1996). STO encodes a Constans-like B-box Zn-finger protein. It has been
shown that STO expression does not change in response to high salt concentrations,
therefore we focused our studies on the pattern expression and the
subcellular localization of the protein in planta, and investigate the possible
functions of STO using a knock out line of Arabidopsis and transgenic plants
overexpressing the protein.
The putative promoter of STO was cloned upstream the GFP and the
expression pattern of the gene was analyzed by epifluorescence microscopy
in transgenic plants. STO becomes expressed in various tissues including
cotyledons, hypocotyls, and roots in dark etiolated seedlings. Similar results
were obtained using GUS as reporter gene. To get experimental evidence of
the subcellular localization in planta, STO was fused to the GFP protein driven
by the constitutive 35S promoter. Transient expression of the GFP::STO fusion
protein in onion cells lead to an accumulation of the protein preferentially
in the nucleus. Similar results were obtained in roots of transgenic dark
etiolated seedlings. Deletion constructs of the STO protein to investigate for
the nuclear localization signal will be analyzed.
We verified an Arabidopsis KO line containing the T-DNA in the first intron of
STO. First results indicate that the KO mutant is in general affected in root
growth. Further investigations on possible phenotypes using the KO and
overexpressor lines will be carried out.
Lippuner V, Cyert MS, and Gasser CS. (1996), J Biol Chem., 271,12859-66.
T04 Interaction with the Environment 1 (Abiotic)