15th International Conference on Arabidopsis Research - TAIR

T04-077
P-regulated transcription factors in Arabidopsis
revealed by comprehensive real-time RT-PCR
Wenming Zheng(1), Rajendra Bari(1), Georg Leggewie(1), Katrin Piepenburg(1),
Michael Udvardi(1), Wolf-Ruediger Scheible(1)
1-Max-Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14424 Potsdam,
Germany
Evolution has endowed plants with an array of adaptive responses to
phosphorous limitation, which are manifest at different levels: morphological;
physiological; and biochemical (Raghothama, 1999). Changes in gene
expression underpin many of these responses, which imply the involvement
of transcription factors (TFs). We are using a reverse-genetics approach to
identify TF genes that orchestrate plant responses to P-stress.
To begin, we developed a real-time RT-PCR resource to profile transcripts of
all known transcription factor (TF) genes in Arabidopsis (Czechowski et al.,
2004). This resource was then used to identify TF genes that are regulated
by changes in phosphate supply. RNA was isolated from ecotype Columbia
plants grown in axenic culture under different P-regimes: Full phosphate nutrition
(1); 48 hours of P-deprivation (2); 30 minutes of phosphate re-supply to
deprived plants (3), and 3 hours of phosphate re-supply (4). Transcript levels
for approximately 1400 TF genes were measured from whole plants exposed
to the four P-treatments, using real-time RT-PCR. Ubiquitin and ß-tubulin
transcript levels were used to normalize the data. Expression of 180 TF genes
changed in response to altered P nutrition (>5-fold changes). Biological
replicates confirmed changes for about half of these. Approximately onethird
of all P-regulated TF genes responded rapidly to phosphate re-addition,
by reversal of their P-deprivation response. Comparisons between RT-PCR
and Affymetrix chip data obtained from the same RNA indicated greater sensitivity
and precision for the former method. Nine P-regulated TF genes have
been selected for further investigation. These will be expressed ectopically in
Arabidopsis, under the control of an alcohol-inducible promoter (Roslan et al.,
2001), before physiological and molecular analysis of the resulting plants.
1, Ann. Rev. Plant Physiol. Plant Mol. Bio. 50, 665-693; 2, Plant J. 28, 225¯235;3, Plant J. 38,
366-379.
15 th <strong>International</strong> <strong>Conference</strong> on Arabidopsis Research 2004 · Berlin
T04-078
LESION SIMULATING DISEASE 1 is required for
acclimation to conditions that promote excess
excitation energy
Alfonso Mateo(1), Per Mühlenbock(1), Christine Rustérucci(3), Chang Chi-
Chen(1), Zbigniew Miszalski(4), Barbara Karpinska(1), Jane E. Parker(3), Philip M.
Mullineaux(2), Stanislaw Karpinski(1)
1-Department of Botany, Stockholm University, Stockholm SE-106 91, Sweden
2-Department of Disease and Stress Biology, John Innes Centre, Colney, Norwich NR4 7UH, United
Kingdom
3-Department of Plant-Microbe Interactions, Max-Planck Institute for Plant Breeding Research,
Carl-von-Linné-Weg 10, D-50829 Cologne, Germany
4-Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek 21, 30-239 Krakow,
Poland
The lsd1 mutant of Arabidopsis thaliana fails to limit the boundaries of hypersensitive
cell death response (HR) during avirulent pathogen infection and
initiates unchecked lesions in long day photoperiod giving rise to the runaway
cell death (rcd) phenotype. We link here the initiation and propagation of
the rcd phenotype to the activity of photosystem II (PSII), stomata conductance
and ultimately to photorespiratory H2O2. The cross of lsd1 with the
chlorophyll a/b binding harvesting-organelle specific (designated gene CAO)
mutant, which has a reduced PSII antenna, led to a reduced lesion formation
in the lsd1/cao double mutant. The mutant had also reduced stomatal
conductance and catalase activity in short-day permissive conditions and induced
H2O2 accumulation followed by rcd when stomatal gas exchange was
further impeded. These traits depended on the defense regulators EDS1 and
PAD4. Furthermore, non-photorespiratory conditions retarded propagation of
lesions in lsd1. In accordance to these observations, we consider that lsd1
failed to acclimate to light conditions that promote excess excitation energy
(EEE) and that LSD1 function was required for optimal catalase activity.
Through this regulation LSD1 can control the effectiveness of photorespiration
in dissipating EEE and consequently be a key determinant of acclimatory
processes. Salicylic acid, which induces stomatal closure, inhibits catalase
activity and triggers the rcd phenotype in lsd1, also impaired acclimation of
wild type plants to conditions that promote EEE. We propose that the roles of
LSD1 in light acclimation and in restricting pathogen-induced cell death are
functionally linked.
Rusterucci et al. (2001) Plant Cell, 13:2211-24.
Willekens et al. (1997) EMBO J, 16: 4806-16
T04 Interaction with the Environment 1 (Abiotic)