TABLE CONTENTS

(3,338) had a lower expression level in syncytia as compared to control roots with a multipletesting
corrected False Discovery Rate below 5%. A Gene Ontology (GO) analysis of up- and
downregulated genes showed that categories related to high metabolic activity were
preferentially upregulated. A principal component analysis was applied to compare the
transcriptome of syncytia with the transcriptome of different Arabidopsis organs obtained by
the AtGenExpress project. This analysis revealed that syncytia are transcriptionally clearly
distinct from roots (and all other organs) and thus form a new organ inside the root.
Among the most strongly upregulated genes in syncytia were MIOX4 and MIOX5, coding
for myo-inositol oxygenase. In plants, UDP-glucuronic acid is synthesized by the oxidation
of UDP-glucose by UDP-glucose dehydrogenase. However a second pathway has been
described and involves the oxidation of free myo inositol by myo-inositol oxygenase. In
Arabidopsis, myo-inositol oxygenase is encoded by four genes (MIOX1, MIOX2, MIOX4,
MIOX5), MIOX3 being a pseudogene. We have started a project to analyze the role of the
MIOX gene family in the development and function of syncytia.
Silencing of Plant Cell Cycle Genes Inhibits Nematode Development
Van de Cappelle, E. (1), E. Plovie (1), J. de Almeida-Engler (2) & G. Gheysen (1)
(1) Department of Molecular Biotechnology, Ghent University, 9000 Ghent Belgium; (2) Department Plant
Microbe Interactions and Plant Health, INRA Sophia Antipolis, France
Inhibitor studies showed that activation of the cell cycle is important for development of
nematode feeding sites (NFS). The aim of this study was to silence expression of cell cycle
genes to interfere with NFS development.
First, the AtCDKA;1 gene was chosen for its importance throughout the cell cycle in
combination with the nematode-induced AtWRKY23 promoter. Transgenic A. thaliana lines
containing inverted repeats of the AtCDKA;1 gene and with reduced AtCDKA;1 expression in
roots, leaves and galls were analysed in more detail. When the lines were infected with the
root-knot nematode Meloidogyne incognita, significantly fewer galls and eggmasses
developed on the roots of the transgenic compared to wild type plants. Infection of the
AtCDKA;1 silenced lines with Heterodera schachtii resulted in a significantly lower number
of cysts compared to the controls. The S266 and S306 lines showed no phenotypic
aberrations in root morphology and analysis at different time points after infection
demonstrated that the number of penetrating nematodes was the same but fewer nematodes
could develop to maturity in the silenced lines. In conclusion, our results demonstrate that
silencing of CDKA;1 can be used as strategy to produce transgenic plants less sensitive to
sedentary plant-parasitic nematodes.
Second, the AtCCS52 gene was choosen for its importance in endoreduplication. Transgenic
A. thaliana lines with hairpin constructs of the AtCCS52 gene in combination with different
promoters were generated and several lines with reduced AtCCS52 expression level and
lower ploidy were shown to be also less susceptible to nematode infection compared to the
controls.
5 th International Congress of Nematology, 2008 177