Biomedical subjects

Odile Chatagnier

Publications and source records attributed to Odile Chatagnier.

3 recordsLinked to original sources

PubMed2004

Fungal elicitation of signal transduction-related plant genes precedes mycorrhiza establishment and requires the dmi3 gene in Medicago truncatula.

Suppressive subtractive hybridization and expressed sequence tag sequencing identified 29 plant genes which are upregulated during the appressorium stage of mycorrhiza establishment between Medicago truncatula J5 (Myc+) and Glomus mosseae. Eleven genes coding plant proteins with predicted functions in signal transduction, transcription, and translation were investigated in more detail for their relation to early events of symbiotic interactions. Expression profiling showed that the genes are activated not only from the appressorium stage up to the fully established symbiosis in the Myc+ genotype of M. truncatula, but also when the symbionts are not in direct cell contact, suggesting that diffusible fungal molecules (Myc factors) play a, role in the induction of a signal-transduction pathway. Transcript accumulation in roots of a mycorrhiza-defective Myc- dmi3 mutant of M. truncatula is not modified by appressorium formation or diffusible fungal molecules, indicating that the signal transduction pathway is required for a successful G. mosseae-M. truncatula interaction leading to symbiosis development. The symbiotic nodulating bacterium Sinorhizobium meliloti does not activate the 11 genes, which supposes early discrimination by plant roots between the microbial symbionts.

Gene Expression Regulation, Plant↗

PubMed2002

Exploring root symbiotic programs in the model legume Medicago truncatula using EST analysis.

We report on a large-scale expressed sequence tag (EST) sequencing and analysis program aimed at characterizing the sets of genes expressed in roots of the model legume Medicago truncatula during interactions with either of two microsymbionts, the nitrogen-fixing bacterium Sinorhizobium meliloti or the arbuscular mycorrhizal fungus Glomus intraradices. We have designed specific tools for in silico analysis of EST data, in relation to chimeric cDNA detection, EST clustering, encoded protein prediction, and detection of differential expression. Our 21 473 5'- and 3'-ESTs could be grouped into 6359 EST clusters, corresponding to distinct virtual genes, along with 52 498 other M.truncatula ESTs available in the dbEST (NCBI) database that were recruited in the process. These clusters were manually annotated, using a specifically developed annotation interface. Analysis of EST cluster distribution in various M.truncatula cDNA libraries, supported by a refined R test to evaluate statistical significance and by 'electronic northern' representation, enabled us to identify a large number of novel genes predicted to be up- or down-regulated during either symbiotic root interaction. These in silico analyses provide a first global view of the genetic programs for root symbioses in M.truncatula. A searchable database has been built and can be accessed through a public interface.

Cluster Analysis↗

PubMedDate not supplied

Repetitive DNA sequences include retrotransposons in genomes of the Glomeromycota.

Twenty-five repetitive elements are first described in the genomes of the arbuscular mycorrhizal (AM) fungi Gigaspora margarita, Gig. rosea and Glomus mosseae. Nineteen repetitive DNA sequences isolated by genomic library screening and four by self-priming PCR had no homology to known DNA sequences, except for two Gig. margarita sequences and one Gig. rosea sequence which showed amino acid similarity to retrotransposons. Part of the Gig. rosea sequence was also similar to a DNA transposon. Two other retrotransposon sequences were isolated using PCR targeting of reverse transcriptase and ribonuclease H domains. Evidence is provided for three gypsy-like LTR retrotransposon and two non-LTR retrotransposon sequences in the AM fungal genomes. Four contain stop codons indicating that they cannot be active. Expression of three retrotransposons was not detected in germinating spores or intraradical hyphae of Gig. margarita. Southern blot analyses indicated that these three sequences are dispersed in the genome and that two are methylated. Sequence analysis of different GmarLTR1 copies showed they have undergone mutations by transitions, which may have been induced by cytosine methylation. Transposable elements may have played a major role in shaping genome structure and size during evolution of the Glomeromycota.

Base Sequence↗