Book of Abstracts - Geyseco

FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology
P10-038: GENETIC EVIDENCE ON THE ROLE OF THE
CLADE A PROTEIN PHOSPHATASE-2C HAB2 IN ABA
SIGNALING
Fernandez-Arbaizar, A. 1 - Nonogaki, H. 2 - Lorenzo, O. 1
1
Centro Hispano-Luso de Investigaciones Agrarias (CIALE)-
Dpto. Fisiología Vegetal. Universidad de Salamanca
2
Department of Horticulture. Oregon State University
Seed biology is a highly topical subject in Plant Biology research.
Essential regulatory molecules, such as abscisic acid
(ABA) and jasmonates (JAs), have been related to seed germination
although most of the molecular bases of the ABA and JAs
action during this developmental cue are currently unknown.
It is well-known that alterations in a concrete signal transduction
pathway may affect plant sensitivity to other hormonal signaling
pathways. In this way, the JA-insensitive mutants coi1-16 and
jar1-1 additionally show ABA-hypersensitive phenotypes being
a good strategy to isolate mutants affected in ABA responses.
Based on this observation, we have developed a screening strategy
to find novel ABA mutants during germination using the JA
insensitive background coi1-16. Screening of 105.000 M2 seedlings
from 17 M1 EMS-mutagenized coi1-16 families, yielded
72 M2 new putative mutants able to supress the coi1-16 ABAhypersensitive
phenotype.
As a proof-of-concept, we have isolated the previously identified
abi1-1 mutant and new alleles of the abi3 and abi4 mutants.
In addition, we have isolated one hypermorphic mutation on
higher arm of Chromosome I, affecting the protein phosphatase
type-2C HAB2 that negatively regulates the ABA signaling
pathway during seed germination. Double mutant hab2;coi1-16
shows aberrant seed development and suppresses coi1-16 hypersensitive
phenotype to the pathogen Botrytiscinerea but not to
Pythiumirregulare. Finally, this mutant is also insenstive to salt
and osmotic stresses, highlighting a key role in the regulation of
ABA responses.
P10-039: TRANSCRIPTIONAL REGULATION OF PHE-
NOLIC COMPOUNDS BIOSYNTHESIS IN GRAPEVINE
(VITIS VINIFERA L.)
Hichri, I. 1 - Bogs, J. 2 - Guillaumie, S. 1 - Mzid, R. 3 - Heppel, S.C. 2 -
Pillet, J. 1 - Czemmel, S. 2 - Mechin, V. 1 - Leon, C. 1
Destrac-Irvine, A.1 - Trossat-Magnin, C,1 - Delrot, S.1 - Lauvergeat,
V.1
1UMR EGFV, France
2Heidelberger Institut Für Pflanzenwissenschaften, Germany
3Centre De Biotechnologie De Borj Cedria, Tunisia
Plant phenolics encompass several classes of molecules such as
stilbenes, flavonoids and lignins, which are involved in many
physiological processes during the plant development. Grape berry
flavonoids, like anthocyanins and condensed tannins, play a
key role in the quality of table fruits and wines. They also display
potential human health benefits due to their powerful antioxidant
activity.The flavonoid pathway is regulated by complexes
of transcription factors belonging to MYB, bHLH and WDR
families. We have identified a grape cDNA encoding a bHLH,
VvMYC1, highly homologous to AN1 which is involved in the
regulation of the anthocyanin pathway in Petunia. Transient promoter
and yeast two-hybrid assays showed that VvMYC1 interacts
with different grape MYB proteins to induce promoters of
flavonoid pathway genes. The co-expression of VvMYC1 and
VvMYBA1 in grape cells induces anthocyanin accumulation.
In addition to VvMYC1 expression pattern in the berry during
development, these results strongly suggest that VvMYC1 is
part of the transcriptional cascade controlling the anthocyanin
and condensed tannins biosynthesis in grapevine (Hichri et al.,
2010).The regulation of lignin biosynthesis has also been investigated.
In addition to impart strength and stiffness to the cell
wall, lignins are essential components in waterproofing vascular
cells, thus enabling the transport of water and solutes through
the plant. We recently showed that overexpression of a WRKY
gene, VvWRKY2, in tobacco, induces modifications of cell wall
structure, xylem development and gene expression in stems and
petioles. In situ hybridization and transient activation assays
confirmed a role of this transcription factor in the regulation of
lignification in grapevine (Guillaumie et al., 2010).
P10-040: TREHALOSE-6-PHOSPHATE AND SUCROSE
SIGNALLING IN ARABIDOPSIS THALIANA
Yadav, U. - Feil, R. - Stitt, M. - Lunn, J.
Max Planck Institute of Molecular Plant Physiology
Trehalose-6-phosphate “(Tre6P)”, the intermediate of trehalose
biosynthesis, plays an essential role in the control of plant metabolism
and growth, although its precise functions are uncertain.
It has been proposed that Tre6P acts as a signalling metabolite
that reflects the availability of sucrose, and thereby regulates the
growth and metabolism of the plant. The aims of the work were
to test the hypothesis that Tre6P is a specific signal of sucrose
status in plants, and to elucidate the upstream signal transduction
pathway linking Tre6P to changes in sucrose levels, using
Arabidopsis thaliana seedlings grown in liquid culture as the experimental
system. Resupply of sucrose to C-starved seedlings
led to rapid and massive “(up to 70-fold)” increases in the level
of Tre6P. Addition of glucose, fructose or maltose also led to a
rise in Tre6P. However, these three sugars also increased sucrose
levels in the seedlings, and in all experiments Tre6P showed a
stronger correlation with sucrose than with glucose or fructose,
irrespective of which sugar was supplied. These results suggested
that the rise in Tre6P was linked to changes in the level of
sucrose, rather than directly to the other sugars. Inhibition of
transcription by cordycepin had little effect on the sucrose-induced
rise in Tre6P. In contrast, inhibition of protein synthesis by
cycloheximide essentially blocked the Tre6P response to sucrose.
The Tre6P response to sucrose is enhanced by treatment of the
seedlings with MG132, which inhibits protein turnover via the
ubiquitin-26S proteasome pathway. Based on these observations,
it is postulated that sucrose induces synthesis of a short-lived regulatory
protein that either activates TPS to increase the rate of
Tre6P synthesis, or inhibits the hydrolysis of Tre6P by TPP.
P10-041: INTERPLAY BETWEEN PHYTOCHROME A
AND RETROGRADE SIGNALLING ESSENTIAL FOR
PLASTID DEVELOPMENT
Kremnev D 1 * - Piñas Fernandéz, A. 2 - Strand, Å. 1
1
Umeå Plant Science Centre
2
University of Edinburgh
*Corresponding author, e-mail: dmitry.kremnev@plantphys.umu.se
Expression of the nuclear genes that encode components of the
photosynthetic apparatus depends on the tightly regulated interaction
between pathways mediated by PHYA and Mg-ProtoIX
during plastid development.
To investigate the role of tetrapyrroles in modulating light signalling,
phyA, gun5 and crd mutants were used. Three experimental
conditions where LHCB1.1 expression in the gun5 mutant is
uncoupled from the state of chloroplast were used to study the
interaction between light and retrograde signalling pathways:
Far-Red block of greening, exposure to continuous Far-Red
light and seedling deetiolation in white light. Far-Red block of
greening treatment is not lethal for the gun5 seedlings and under
continuous Far-Red light the gun5 seedlings accumulate higher
amounts of LHCB1.1 transcript compared to wild type and the
crd mutant. During the first four hours of white light illumination,
expression of LHCB1.1 is higher in gun5 and lower in crd
compared to wild type. Similarly to the crd mutant, the phyA
seedlings show a delay in LHCB1.1 transcript accumulation.
Analysis of tetrapyrrole content revealed that Mg-ProtoIX acts
as a negative regulator of PHYA driven expression of nuclear encoded
photosynthesis genes. Taken together our results indicate