Book of Abstracts - Geyseco

FESPB 2010 - XVII Congress of the Federation of European Societies of Plant Biology
the expression of PID and WAG2 kinase genes, thus affecting the
subcellular localisation of PIN auxin efflux carriers and creating
an auxin minimum necessary for VM formation. Our recent
work, primarily based on expression analysis and ChIP experiment,
has led to the identification of two other IND-dependant
pathways required for proper development of VM tissues. IND
directly regulates Gibberellins biosynthesis, which appears to be
crucial as a local depletion in bioactive Gibberellins affect the
formation of VMs. IND also directly activates the expression of
SPATULA (SPT), a bHLH-encoding gene previously described
in the patterning of other fruit tissues. IND and SPT proteins interact
when expressed in epidermal onion cells and in yeast, and
the analysis of over-expressing Arabidopsis lines suggests that
this interaction is important for the function of the proteins in
planta. Finally, phenotypic analysis of single and double mutants
shows that IND and SPT are together required for the patterning
of several fruits tissues ; this leads to the identification of previously
unknown roles for IND in stigma and transmitting tract
formation and for SPT in VM development. Cross talks between
the three IND-regulated pathways involved in VM patterning
will be discussed.
P04-021: B-FUNCTION MADS-BOX GENES IN LEGU-
MES: GENE DUPLICATION AND SUBFUNCTIONALI-
ZATION IN MEDICAGO TRUNCATULA
Roque, E.* - Rochina, MC. – Serwatowska, J. – Yenush, L. - Beltrán
J.P. - Cañas L.A.
Instituto de Biología Molecular y Celular de Plantas (CSIC-
UPV)
*Corresponding author e-mail: edroque@ibmcp.upv.es
Using the MADS-box of the AmDEFICIENS gene as a probe to
screen a floral cDNA library of Medicago truncatula, we have
isolated four B-function genes involved in the specification of
petal and stamen identity: two APETALA 3 (MtAP3 and MtN-
MH7) and two PISTILLATA (MtPI and MtNGL9) orthologs. The
expression patterns of these genes have been studied by in situ
hybridization analysis and we have also performed two-hybrid
assays to identify possible protein-protein interactions. Both
MtPI and MtNGL9 proteins lack the PI motif described as essential
for the functionality of PISTILLATA in Arabidopsis. Using
RNAi and Tnt1 mutagenesis, we generated MtPI loss-of-function
mutants. These plants showed flowers with sepaloid petals and
carpelloid stamens. Our results suggest that the differences in the
functional constrictions among the paralogs MtPI and MtNGL9
could have generated a high degree of structural conservation in
MtPI, which maintains a predominant role during floral development,
whereas MtNGL9 could have accumulated mutations
in the expression activation elements of the regulatory regions,
in addition to acquiring new cis-regulatory elements, thus providing
new spatial expression patterns. Therefore, these genes
could have followed a quantitative subfunctionalization process
in parallel, followed by a possible neofunctionalization process.
The M. truncatula AP3 orthologs could have undergone
a qualitative subfunctionalization with the subsequent partition
of the ancestral functions. This hypothesis is reinforced by the
non-overlapping spatial expression patterns in the 2nd and 3rd
floral whorls and by the phenotypes of partial loss-of-B function
in both mutants.
P04-022: GENOME-WIDE ANALYSIS OF FLORAL OR-
GAN FORMATION
Raganelli, A.* - Wellmer, F.
Smurfit Institute of Genetics Trinity College Dublin
*Corresponding author e-mail: andrea.raganelli@gmail.com
How complex organs are formed by multicellular organisms
is a key question in developmental biology. Flower formation
is an excellent system for studying the molecular mechanisms
underlying organogenesis in plants. Several genes that control
flower development have been identified in the model plant
Arabidopsis thaliana but only few of them are known to specifically
control the formation of the different types of floral
organs, i.e.: sepals, petals, stamens and carpels. Most of these
genes encode transcription factors or other proteins involved in
the regulation of transcription, indicating the existence of a complex
gene regulatory network that underlies flower development.
Nevertheless, the target genes of the known transcriptional regulators,
the regulatory elements, and how these genes interact is
still for the most part unknown. We focus on the dissection of the
genes network that underlies floral organ formation by the identification
and functional characterization of target genes of key
regulatory transcription factors at a global level. To this end, we
are generating and testing different induction systems to separately
control the onset of flowering with a floral induction system
that allows the isolation of a large number of synchronized floral
buds and the expression of artificial microRNAs (amiRNAs) directed
against the transcription factor analyzed. This will enable
us to specifically knock down the expression of floral regulators
at different stages of flower development and through the use of
genome-wide expression profiling by DNA microarray analysis,
to identify the downstream responsive genes.
P04-023: FUNCTIONAL STUDY OF TRANSCRIPTION
FACTORS POTENTIALLY INVOLVED IN THE JUVENI-
LE TO ADULT PHASE TRANSITION IN CITRUS
Castillo, MC.¹* - Gas, M.E.² - Navarro, L.¹ - Ancillo, G.¹
¹Instituto Valenciano Investigaciones Agrarias
²Institut de Génétique et de Biologie Moléculaire et Cellulaire
*Corresponding author e-mail: mccastillo@ivia.es
In higher plants, development has two different phases, juvenile
and adult. Plants are not reproductively competent until they
reach the adult phase. In citrus the juvenile phase can be as large
as 5-20 years depending on the variety what is a serious constraint
for molecular and conventional breeding of citrus genotypes.
With the aim of identifying regulatory genes involved in the process
of juvenile to adult phase transition we developed a citrus
transcription factors (TF) microarray, and used it to screen for TF
differentially expressed between juvenile and adult plants in four
citrus species: Sweet Orange (C. sinensis (L.) Pineapple), Tangor
Murcott (C. reticulata x C. sinensis), Grapefruit (C. paradisi
Macf. Duncan) and Rough Lemon (C. limon (L.)). Several transcription
factors were identified as differentially expressed. Some
of these genes showed high homology with MADS-box genes
which are a diverse class of TF that are involved in regulating developmental
processes, particularly meristem and organ identity
during floral development. On the other hand, some other genes
showed no significant homology to genes of known function, indicating
that they may be specific factors. Since the juvenility in
citrus and Arabidopsis has differential aspects, those genes could
be good candidates to study these particular aspects.
To deep into their functional study, transgenic Arabidopsis lines
over expressing some of these genes have been generated. Number
of leaves without abaxial trichomes, flowering time and morphology
of leaves, siliques and hole plant have been analysed.
Some lines showed shortening of the juvenile phase, indicating
that those genes are most likely involved in determining the reproductive
phase transition in citrus.
P04-024: STRUCTURE AND DNA BINDING SPECIFICI-
TY OF THE LEAFY FLORAL TRANSCRIPTION FAC-
TOR
Moyroud, E. – Blanchet, S. – Minguet, E.G.* – Hames, C. – Thevenon,
E. – Parcy, F.
Physiologie Cellulaire Végétale. CNRS-INRA-CEA-UJF
*Corresponding author e-mail: eugeniogomez@ono.com
The LEAFY gene is present in all land plant and plays a central
role in flower development of angiosperms [1]. It encodes a plant