Book of Abstracts - Geyseco

P - Posters
growth and development as specific phenotypes related to sugar
partitioning, carbon allocation and stress resistance were found.
This is more linked to the change in the level of the intermediate
Trehalose-6-Phosphate (T6P), which is strongly related to
sugar status, than to T itself. Arabidopsis has 21 genes putatively
involved in T biosynthesis, only one has showed T6P synthase
activity and surprisingly 10 of them, known as T6P Phosphatases
(TPPA-TPPJ), are active TPPs. Identification of TPP promoter
cell-type activity revealed specific expression patterns of these
genes in different organs of the plant. By analyzing loss and gain
of function mutants we could find that some TPPs are involved
in the development of lateral root primordia and their outgrowth.
Phenotypes related to the formation of flowers and high/low biomass
have been found also. These observations suggest that TPP
genes could be tightly controlling T6P levels in particular cells
and times of plant growth instead of producing more or less T.
Nevertheless sugars, T6P and metabolite measurements are needed
to confirm this hypothesis and to understand why T metabolism
is so relevant for plant growth.
P06-018: BELOWGROUND VOLATILES FROM WHEAT
(TRITICUM AESTIVUM L.) AND FROM PLANT
GROWTH-PROMOTING BACTERIA OF THE WHEAT
RHIZOSPHERE
du Jardin, P.* - Delaplace, P. - Ormenõ, E. - d’Ans, S. - Fauconnier,
M.L. - Wathelet, J.P.
University of Liège - Gembloux Agro-Bio Tech
*Corresponding author e-mail: patrick.dujardin@ulg.ac.be
The relevance of organic volatile compounds (VOC) released
by leaves in plant–to–plant communication and in the interaction
with herbivores, pathogens and their natural enemies is well
acknowledged, but their roles in the root environment are much
less known. In order to contribute to the unravelling of the nature,
origins and functions of volatiles emitted by roots, wheat
(Triticum aestivum L.) was chosen as a model with the aim to
characterize VOC-mediated interactions between roots and rhizospheric
bacteria defined as promoters of plant growth („Plant
Growth Promoting Bacteria, or PGPRs). Regarding the plant
partner, three questions were first raised: what is the profile of
extractable volatiles of roots (in the absence of biotic or abiotic
stress), how similar/different is this profile with that of leaf volatiles,
and do the released volatiles match the extractable VOCs
found within the root organs? Regarding the bacterial partners,
19strains from 8 genera (Azospirillum, Azotobacter, Bacillus,
Burkholderia, Paenibacillus, Pseudomonas, Raoultella, Serratia)
were selected. Their growth parameters were defined in order
to standardize the physiological conditions used when analyzing
their VOC emissions. Volatiles were analysed by gas chromatography
– mass spectrometry (GC-MS) after both extraction from
plant tissues and adsorption of the released volatiles on solidphase
micro-extraction fibers. The results indicate that wheat
roots produce and release a blend of VOCs mainly derived from
the enzymatic oxydation of unsaturated fatty acids. Preliminary
results on the VOC profiling of the selected rhizobacteria will
also be presented.
P06-019: RETINOBLASTOMA-RELATED PROTEIN
CONTROLS ROOT EPIDERMAL CELL DIFFERENTIA-
TION IN ARABIDOPSIS THALIANA.
Desvoyes, B. - Gutierrez, C.
Centro de Biología Molecular Severo Ochoa, CSIC-UAM
The role of the retinoblastoma related protein (RBR) in restricting
cells to enter S-phase by modulating the activity of E2F
transcription factors is now well established. New roles of RBR
in cell differentiation processes are now emerging. To assess the
relevance of the RBR pathway in cell fate specification we are
using Arabidopsis root epidermal cells as a model. Root epidermal
cells are generated at the root apical meristem and differentiate
either in hair or hairless cells in a cell-position dependent
manner. The genetic network that control root hair cell patterning
is well known and relies on the expression of the homeodomain
protein GLABRA2 (GL2), an inhibitor of hair cell specification.
Ectopic expression of RBR prevents cell proliferation of meristematic
cells and alters cell fate specification provoking the
appearance of ectopic hairs. Likewise, inactivation of RBR by
expression of the RBR-binding RepA protein affects root hair
patterning. We will present evidence that RBR is implicated in
the control of epidermal cell fate in a dual manner: one that is
cell cycle-dependent and, another by regulating specifically the
expression of cell fate genes. Our study identifies a novel role of
RBR in linking cell proliferation control and cell fate determination
during root growth.
P06-020: LOCAL SUPPLY OF IRON DISTINCTLY DEFI-
NES LATERAL ROOT NUMBER AND ELONGATION IN
ARABIDOPSIS THALIANA
Ricardo F. H. Giehl* - Joni E. Lima - Nicolaus von Wirén
University of Hohenheim
*Corresponding author e-mail: hetgiehl@yahoo.com.br
Morphological adaptations of the root system to a localized nutrient
source are seen as an indication for nutrient sensing by
plant roots. With regard to the low mobility of iron (Fe) in soils,
we investigated changes in the root system architecture of Arabidopsis
plants in response a localized supply of Fe. Increasing Fe
concentrations in a homogenous or localized supply on separated
agar plates enhanced lateral root number in a similar manner.
Lateral root length, however, was twofold higher under localized
relative to homogenous Fe supply. With further increasing
Fe concentrations lateral root length was repressed even though
shoot growth was unaffected. Observing early lateral root development
by the use of CYCB1::GUS reporter lines indicated that
in particular the emergence of lateral root initials was stimulated
by local Fe. We then investigated lateral root growth in the
Fe uptake-defective mutant irt1 and in the frd3-1 mutant, which
is defective in root-to-shoot translocation of Fe. Based on these
observations we propose a differential regulation of lateral root
initiation and elongation in response to localized Fe supply that is
subject to a local regulation by Fe and involves the high-affinity
Fe transporter IRT1.
P06-021: ANATOMICAL CHARACTERIZATION OF
ROOT SYSTEM OF MAIZE MUTANT LRT1
Husáková, E. - Soukup, A.
Charles University in Prague, Faculty of Science, Department of
Experimental Plant Biology
Maize mutant lrt1 (lateral rootless1) is one of few mutants out of
Arabidopsis with defect in lateral root formation. Since its description
we present the first detailed anatomical-histochemical
analyse along the developing main root.
Mutant lrt1 was described as incapable of lateral root initiation
during early post germination growth. Our data indicate that lrt1
competency to initiate of the lateral root primordium is highly
dependent on environmental factors. However, lrt1 primordia
didn’t emerge from the main root, their cells are more vacuolized
and the cellular organization of primordia is affected coparing
to wildtype. Disturbances with oxidized polyphenolic substances
were often found in pericycle where initiation normaly takes
place. The outer layers of lrt1 cortex were disorganized and
continual ring of exodermal layers were also interrupted. The
permeability test of root surface detected changes in exodermis
function. Strong activity of peroxidase was detected in all tissues
of lrt1 root. The highest activity appeared in central cylinder,
mainly in pericycle, and in the subepidermal layers of the root.
Our results indicate, that phenotypical traits described for the
mutant might be related to cell wall modifications and subsequent
higher rigidity of cell walls and/or differentiation of cells.
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