Book of Abstracts - Geyseco

P - Posters
Atkinson, N.* - Urwin, P.E-
University of Leeds
*Corresponding author e-mail: bsnjsj@leeds.ac.uk
Plants respond to different biotic and abiotic stresses using specific
gene signalling pathways leading to stress tolerance or acclimation.
Traditionally each stress and its molecular effect on a
plant have been studied independently, although field environments
are likely to present coincident stresses. Recent research
suggests that the molecular and metabolomic reaction of plants
to multiple stresses is different to that for individual stresses. Furthermore
it has been found that stress signalling pathways may act
antagonistically. To fully understand the nature of plant responses
it is therefore essential to study stress factors in combination.
In this study Affymetrix ATH1 microarray chips were used to
study the transcriptome response of Arabidopsis thaliana to combined
abiotic and biotic stress. Plants were exposed to infection
by the plant-parasitic nematode Heterodera schachtii and then
subjected to drought stress by dehydration under stringently controlled
conditions. The response of plants to combined drought
stress and nematode infection was found to be distinct from that
of each stress individually. In roots 1067 gene transcripts were
differentially regulated specifically in response to joint stress (P <
0.05) whilst in leaves 1282 such genes were identified. Transcription
factors were highly represented amongst these gene subsets,
as well as genes induced by stress signalling-related hormones
abscisic acid and jasmonic acid. Thus a new pattern of multiple
stress defence response has been identified. The identification of
genes controlling the crossover between multiple stress signalling
pathways may provide opportunities for the future development
of broad-spectrum stress tolerant crops.
P07-018: CATION SELECTIVITY OF THE NA+/H+ EX-
CHANGER ATSOS1
Feki, k. 1 * - Pardo, J. M. 1 - Masmoudi, K. 2 - Quintero, F.J 1
1
Instituto de Recursos Naturales y Agrobiología de Sevilla (CSIC)
2
Center of Biotechnology of Sfax
*Corresponding author e-mail: kaouther_feki@yahoo.fr
The plasma membrane Na + /H + antiporter AtSOS1 is a key determinant
for salt tolerance. This protein mediates Na + extrusion
from plant cells and shows a high specificity for Na + in biochemical
and in vivo assays. Interestingly, the Arabidopsis transporter
AtNHX8, phylogenetically related to AtSOS1, was characterized
as a Li + /H + antiporter with little affinity for Na + . Although the
substrate specifity is different in the two proteins, they show a
high degree of similarity at the protein sequence level. Little is
known about topological determinants involved in the cation specifity
of antiporters. Critical residues of the pore domain and the
regulatory cytosolic
C-terminal domains are both thought to be important. We have
studied the effect of the C-terminal part of the Arabidopsis proteins
in the process of cation selectivity. The C-terminal regions
of AtSOS1 and AtNHX8 were swapped and the transport activity
of the chimerical proteins was analyzed in a Na + and Li + sensitive
yeast strain. Results supporting a role for the C-terminal region
in determining the substrate specificity of the transporter will be
presented.
P07-019: GENETIC AND PHYSIOLOGICAL ANALYSES
OF THE ROLE OF VACUOLAR NHX EXCHANGERS IN
POTASSIUM METABOLISM
Andrés González, Z.* - Andrés, Z. - Barragán, V. - Leidi, E. O. -
Pardo, J. M. - Cubero, B.
Instituto de Recursos Naturales y Agrobiología de Sevilla (IR-
NASE-CSIC)
*Corresponding author e-mail: zandres@irnase.csic.es
The physiological role of tonoplast NHX-type cation/H+ antiporters
is thought to relate mainly to the plant salt stress response by
mediating compartmentation of Na+ in vacuoles. However, all
isoforms characterized so far catalyze both Na+/H+ and K+/H+
exchange. Genetic evidence will be presented that the regulation
of K+ homeostasis by NHX-type antiporters is essential for normal
plant growth and development, and plays an important role
in the response to osmotic stress by improving K+ accumulation.
Thus, NHX-typeproteins are likely candidates for the H+-linked
K+-transport that is thought to facilitate active K+ uptake at the
tonoplast and the partitioning of K+ between vacuole and cytosol.
This critical function should be taken into consideration for
understanding the salt tolerance phenotype of plants overexpressing
NHX-type exchangers.
P07-020: PIN-DRIVEN AUXIN REGULATION OF SHADE
AVOIDANCE
Keuskamp, D.* - Voesenek, L. A. C. J. - Pierik, R.
Plant Ecophysiology, Institute of Environmental Biology , Utrecht
University
*Corresponding author e-mail: d.h.keuskamp@uu.nl
Plants usually grow in a dynamic environment with oftentimes
severe competition for light with surrounding neighbours. As a
result, not only light intensity is affected, but also the light quality
and the latter is exploited by plants to sense neighbours. Light
quality signals are a reduced red to far-red ratio (R:FR) and blue
light depletion, which are perceived by the phytochrome and
cryptochrome photoreceptors respectively. These signals can
independently induce shade avoidance responses, which include
shoot elongation to consolidate light capture. It has been shown
for low R:FR-exposed plants that elevated auxin levels1 and proper
auxin transport2 are essential to this response. We show here
that PIN proteins, which control polar auxin transport (PAT), are
essential regulators of light quality-mediated shoot elongation in
Arabidopsis. We show that low R:FR conditions regulate PINs at
both the transcriptional level and cellular location. Knockout mutants
display inhibited shade avoidance responses to low R:FR
and are consequently out-competed in dense stand mixtures with
WT neighbours. These data show how auxin transport is regulated
to control shade avoidance responses, and how this regulation
determines plant competitive vigour.
1) Tao Y, et al. Cell 2008; 133:164-176.
2) PierikR, et al. Plant Physiol 2009; 149:1701-1712.
P07-021: OVEREXPRESSION OF ARABIDOPSIS CO-
PPER TRANSPORTERS AFFECTS THE EXPRESSION
OF CCA1 AND LHY CIRCADIAN CLOCK COMPO-
NENTS
Andrés-Colás, N.* - Perea-García, A. - Puig, S. - Peñarrubia, L.
Universitat de València
nuria.andres@uv.es
Copper is an essential cofactor for key processes in plants, but it
becomes harmful when in excess. The overexpression of either
Arabidopsis COPT1 or COPT3 high affinity copper transporters
in transgenic plants drives increased endogenous copper levels
and sensitivity to the copper in the growth medium. Additional
phenotypes include decreased hypocotyls growth in red light and
differentially affected flowering times depending on the photoperiod,
as well as compromised plant survival in the absence of
environmental cycles such as light and temperature. Furthermore,
the expression of the nuclear circadian clock genes CCA1 and
LHY is substantially reduced in these transgenic plants. Copper
induces the down-regulation of the expression of CCA1 and
LHY in wild type plants and it also drives a reduction in the expression
of circadian clock output genes. These results reveal that
the spatial-temporal control of copper transport is a key aspect
of metal homeostasis that is required for Arabidopsis fitness, especially
in the absence of environmental clues. In this sense, Cu
homeostasis could participate in the integral cellular circadian
system, possibly through the effect of Cu on the expression of
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