Biomedical subjects

Pierre Abad

Publications and source records attributed to Pierre Abad.

15 recordsLinked to original sources

PubMed2006

Characterization of a new beta-1,4-endoglucanase gene from the root-knot nematode Meloidogyne incognita and evolutionary scheme for phytonematode family 5 glycosyl hydrolases.

Cellulases from plant parasitic nematodes are encoded by multiple gene families and are thought to originate from horizontal gene transfer. Unraveling the evolution of these genes in the phylum will help understanding the evolution of plant parasitism in nematodes. Here we describe a new gene, named MI-eng-2, that encodes a family 5 glycosyl hydrolase (GHF5) with a predicted signal peptide and devoid of linker domain and cellulose-binding domain. The beta-1,4-endoglucanase activity of the protein MI-ENG-2 was confirmed in vitro and the transcription of the gene was localized in the secretory oesophageal glands of infective juveniles, suggesting that MI-ENG-2 is involved in plant cell wall degradation during parasitism. Phylogenetic and exon/intron structure analyses of beta-1,4-endoglucanase genes in the order Tylenchida strengthen the hypothesis that nematode GHF5 genes result from horizontal gene transfer of a bacterial gene with a cellulose-binding domain. GHF5 gene families in Tylenchida result from gene duplications associated with occasional loss of the cellulose-binding domain and the linker domain during their evolution.

Amino Acid Sequence↗

PubMed2005

Conserved and variable domains in satellite DNAs of mitotic parthenogenetic root-knot nematode species.

Two satellite DNAs have been characterized in the mitotic parthenogenetic root-knot nematodes Meloidogyne javanica and M. paranaensis, agriculturally important phytoparasitic species. The satellite repeat variants cloned from M. javanica could not be resolved from those described earlier in M. arenaria [Castagnone-Sereno, P., Leroy, F., Abad, P., 2000. Cloning and characterization of an extremely conserved satellite DNA family from the root-knot nematode Meloidogyne arenaria. Genome 43, 346-353] and are therefore classified as a single satellite named MARJA. However, this satellite shows 34.3% sequence divergence in comparison with the MPA1 satellite characterized in M. paranaensis, and monomer variants of both satellites are clearly distinguished by homogenized nucleotide substitutions. Nucleotide variability analysis revealed in one segment of the satellite monomer domains of high and low variability, conserved both within and between monomer variants of the two satellites. Intersatellite conservation of these domains indicates evolution of satellite sequence under different constraints, probably due to some functional interactions. In addition, high intrasatellite homogeneity, presence of ancestral mutations in groups of MARJA monomers in both M. javanica and M. arenaria and highly homogenized divergent positions in comparison with the MPA1 indicate similar sequence dynamics in mitotic parthenogenetic taxa to that observed in amphimictic species.

Amino Acid Sequence↗

PubMed2005

Loss of susceptibility as an alternative for nematode resistance.

Among plant pathogens, sedentary endoparasitic nematodes are one of the most damaging pests in global agriculture. These obligate parasites interact with their hosts in a quite unique and intriguing way. They induce the redifferentiation of root cells into specialized feeding cells essential for nematode growth and reproduction; thus, nematodes have evolved the ability to exploit plant genes and hijack host functions for their own requirements. Various approaches to engineer plants with resistance to parasitic nematodes have been pursued, most focusing on the introduction of resistance genes. An alternative strategy to achieve resistance is to exploit the susceptibility of plant disease. Better knowledge of the plant response during the compatible interaction should allow the identification of targets to engineer resistance to parasitic nematodes in crop species.

Alleles↗

PubMed2005

In planta secretion of a calreticulin by migratory and sedentary stages of root-knot nematode.

Esophageal secretions from endoparasitic sedentary nematodes are thought to play key roles throughout plant parasitism, in particular during the invasion of the root tissue and the initiation and maintenance of the nematode feeding site (NFS) essential for nematode development. The secretion in planta of esophageal cell-wall-degrading enzymes by migratory juveniles has been shown, suggesting a role for these enzymes in the invasion phase. Nevertheless, the secretion of an esophageal gland protein into the NFS by nematode sedentary stages has never been demonstrated. The calreticulin Mi-CRT is a protein synthesized in the esophageal glands of the root-knot nematode Meloidogyne incognita. After three-dimensional modeling of the Mi-CRT protein, a surface peptide was selected to raise specific antibodies. In planta immunolocalization showed that Mi-CRT is secreted by migratory and sedentary stage nematodes, suggesting a role for Mi-CRT throughout parasitism. During the maintenance of the NFS, the secreted Mi-CRT was localized outside the nematode at the tip of the stylet. In addition, Mi-CRT accumulation was observed along the cell wall of the giant cells that compose the feeding site, providing evidence for a nematode esophageal protein secretion into the NFS.

Amino Acid Sequence↗

PubMed2005

Genome-wide expression profiling of the host response to root-knot nematode infection in Arabidopsis.

During a compatible interaction, root-knot nematodes (Meloidogyne spp.) induce the redifferentiation of root cells into multinucleate nematode feeding cells (giant cells). Hyperplasia and hypertrophy of the surrounding cells leads to the formation of a root gall. We investigated the plant response to root-knot nematodes by carrying out a global analysis of gene expression during gall formation in Arabidopsis, using giant cell-enriched root tissues. Among 22 089 genes monitored with the complete Arabidopsis transcriptome microarray gene-specific tag, we identified 3373 genes that display significant differential expression between uninfected root tissues and galls at different developmental stages. Quantitative PCR analysis and the use of promoter GUS fusions confirmed the changes in mRNA levels observed in our microarray analysis. We showed that a comparable number of genes were found to be up- and downregulated, indicating that gene downregulation might be essential to allow proper gall formation. Moreover, many genes belonging to the same family are differently regulated in feeding cells. This genome-wide overview of gene expression during plant-nematode interaction provides new insights into nematode feeding-cell formation, and highlights that the suppression of plant defence is associated with nematode feeding-site development.

Animals↗

PubMed2004

Arabidopsis formin AtFH6 is a plasma membrane-associated protein upregulated in giant cells induced by parasitic nematodes.

Plant-parasitic nematodes Meloidogyne spp induce an elaborate permanent feeding site characterized by the redifferentiation of root cells into multinucleate and hypertrophied giant cells. We have isolated by a promoter trap strategy an Arabidopsis thaliana formin gene, AtFH6, which is upregulated during giant cell formation. Formins are actin-nucleating proteins that stimulate de novo polymerization of actin filaments. We show here that three type-I formins were upregulated in giant cells and that the AtFH6 protein was anchored to the plasma membrane and uniformly distributed. Suppression of the budding defect of the Saccharomyces cerevisiae bni1Delta bnr1Delta mutant showed that AtFH6 regulates polarized growth by controlling the assembly of actin cables. Our results suggest that AtFH6 might be involved in the isotropic growth of hypertrophied feeding cells via the reorganization of the actin cytoskeleton. The actin cables would serve as tracks for vesicle trafficking needed for extensive plasma membrane and cell wall biogenesis. Therefore, determining how plant parasitic nematodes modify root cells into giant cells represents an attractive system to identify genes that regulate cell growth and morphogenesis.

Actins↗

PubMed2003

Characterization of Mcmar1, a mariner-like element with large inverted terminal repeats (ITRs) from the phytoparasitic nematode Meloidogyne chitwoodi.

Two copies of a new mariner-like element (MLE) presenting unusual inverted terminal repeats (ITRs), Mcmar1-1 and Mcmar1-2, were cloned and sequenced in the genome of the phytoparasitic nematode Meloidogyne chitwoodi. Although the sequence features of these Mcmar1 transposons are commonplace and link them to the mariner family, at their extremities they have large 355-pb long inverted terminal repeats that are perfectly conserved. This characteristic distinguishes them from all the other MLEs so far described that have imperfectly conserved ITRs of about 26-30 bp. In consequence, the sequenced full-length Mcmar1-1 element is 2000 bp long, and comprises an uninterrupted open reading frame (ORF) that encodes a putatively active transposase with 340 amino acid residues. The Mcmar1-2 element is a deleted form of Mcmar1-1 that contains a deletion overlapping most of the internal region of the 5'ITR and the 5' region of the transposase ORF. The presence of large ITRs in different transposons related to the Tc1-mariner super-family is discussed.

Amino Acid Sequence↗

PubMed2003

A set of genes differentially expressed between avirulent and virulent Meloidogyne incognita near-isogenic lines encode secreted proteins.

A cDNA-amplification fragment length polymorphism (AFLP)-based strategy has been used to identify genes differentially expressed between two pairs of near-isogenic lines (NIL) of the root-knot nematode Meloidogyne incognita either avirulent or virulent against the tomato Mi resistance gene. Gene expression profiles from infective second-stage juveniles (J2) were compared, and 22 of the 24,025 transcript-derived fragments (TDF) generated proved to be differential, i.e., present in both avirulent NIL and absent in both virulent NIL. Fourteen of the TDF sequences did not show any significant similarity to known proteins, while eight matched reported sequences from nematodes and other invertebrates. The differential expression of nine genes was confirmed by reverse transcription-polymerase chain reaction (RT-PCR) experiments. In situ hybridization conducted with five of the sequences showed that two were specifically expressed in the intestinal cells (HM10 and PM1), one in the subventral esophageal glands (HM1), and two in the dorsal esophageal gland of J2 (HM7 and HM12). Analysis of full-length cDNA sequences revealed the presence of a signal peptide for HM1, HM10, and HM12, indicating that the encoded proteins are putatively secreted. Since secreted products in general and esophageal gland secretions in particular are thought to be among the main M. incognita pathogenicity factors, this result suggests a possible dual role for some of the genes encoding such secretions, i.e., they could be involved in both pathogenicity and virulence or avirulence of these biotrophic parasites.

Animals↗

PubMed2003

The Medicago species A2-type cyclin is auxin regulated and involved in meristem formation but dispensable for endoreduplication-associated developmental programs.

Phytohormones as well as temporal and spatial regulation of the cell cycle play a key role in plant development. Here, we investigated the function and regulation of an alfalfa (Medicago sativa) A2-type cyclin in three distinct root developmental programs: in primary and secondary root development, nodule development, and nematode-elicited gall formation. Using transgenic plants carrying the Medsa;cycA2;2 promoter-beta-glucuronidase gene fusion, in combination with other techniques, cycA2;2 expression was localized in meristems and proliferating cells in the lateral root and nodule primordia. Rapid induction of cycA2;2 by Nod factors demonstrated that this gene is implicated in cell cycle activation of differentiated cells developing to nodule primordia. Surprisingly, cycA2;2 was repressed in the endoreduplicating, division-arrested cells both during nodule development and formation of giant cells in nematode-induced galls, indicating that CycA2;2 was dispensable for S-phase in endoreduplication cycles. Overexpression of cycA2;2 in transgenic plants corresponded to wild type protein levels and had no apparent phenotype. In contrast, antisense expression of cycA2;2 halted regeneration of somatic embryos, suggesting a role for CycA2;2 in the formation or activity of apical meristems. Expression of cycA2;2 was up-regulated by auxins, as expected from the presence of auxin response elements in the promoter. Moreover, auxin also affected the spatial expression pattern of this cyclin by shifting the cycA2;2 expression from the phloem to the xylem poles.

Animals↗

PubMed2002

A polygalacturonase of animal origin isolated from the root-knot nematode Meloidogyne incognita.

The first animal polygalacturonase (PG, EC 2.1.15) encoding cDNA, Mi-pg-1, was cloned from the plant parasitic nematode Meloidogyne incognita. The enzymatic activity of MI-PG-1 was confirmed after heterologous expression in Escherichia coli. The presence of a predicted signal peptide on the MI-PG-1 sequence together with the specific localization of the transcripts of the Mi-pg-1 gene in the oesophageal glands of infective juveniles imply that MI-PG-1 could be secreted into plant tissues. The potential role of MI-PG-1 in parasitism is discussed.

Animals↗

PubMed2002

Direct identification of stylet secreted proteins from root-knot nematodes by a proteomic approach.

The stylet secretions produced by plant parasitic root-knot nematodes are thought to be pathogenicity factors involved in the invasion of the root tissue and in the induction and maintenance of feeding cells. A new procedure was established that allowed the direct qualitative analysis of proteins secreted by Meloidogyne incognita infective juveniles. Purified proteins whose isoelectric point (pI) ranged from 5.0 to 7.5 were separated by two-dimensional (2D) electrophoresis and the seven most abundant proteins were identified by micro-sequencing. A calreticulin (CRT) was isolated and transcription of its gene in infective juveniles and adults was demonstrated. Moreover, evidence for expression of the CRT in the subventral oesophageal glands of infective juveniles was obtained. The potential roles of this secreted protein in pathogenesis and the advantages of developing this strategy to obtain new insights into plant-nematode interactions are discussed.

Amino Acid Sequence↗

PubMed2002

Flanking sequence tags in Arabidopsis thaliana T-DNA insertion lines: a pilot study.

Eight hundred and fifty Arabidopsis thaliana T-DNA insertion lines have been selected on a phenotypic basis. The T-DNA flanking sequences (FST) have been isolated using a PCR amplification procedure and sequenced. Seven hundred plant DNA sequences have been obtained revealing a T-DNA insertion in, or in the immediate vicinity of 482 annotated genes. Limited deletions of plant DNA have been observed at the site of insertion of T-DNA as well as in its left (LB) and right (RB) T-DNA signal sequences. The distribution of the T-DNA insertions along the chromosomes shows that they are essentially absent from the centrometric and pericentrometric regions.

Arabidopsis↗

PubMed2002

Characterization of a cDNA related to K-Cl Cotransporters in the root-knot nematode Meloidogyne incognita.

We report the cloning of a full-length cDNA from the plant-parasitic nematode Meloidogyne incognita, which encodes a putative protein of 1082 amino acids showing high similarity with K-Cl cotransporters (KCCs) from the free-living nematode Caenorhabditis elegans (54% identity) and from a number of mammals, including human. Hydropathy analysis indicates typical KCC topology patterns, with a hydrophylic NH2-terminal region, 12 membrane-spanning domains, and a long COOH-terminal hydrophylic region. Alignment of the nematode sequences with eleven KCC sequences from mammals suggests that the nematode proteins may constitute a separated family of KCCs. The M. incognita gene was shown to be expressed in both motile and sedentary stages, which suggests an important function in general physiology of the nematode. By analogy with known proteins, it is hypothesized that this gene is involved in the regulation of cell osmotic pressure to maintain nematode body fluids hyperosmotic to the environment.

Amino Acid Sequence↗

PubMed2002

The endosymbiosis-induced genes ENOD40 and CCS52a are involved in endoparasitic-nematode interactions in Medicago truncatula.

Plants associate with a wide range of mutualistic and parasitic biotrophic organisms. Here, we investigated whether beneficial plant symbionts and biotrophic pathogens induce distinct or overlapping regulatory pathways in Medicago truncatula. The symbiosis between Sinorhizobium meliloti and this plant results in the formation of nitrogen-fixing root nodules requiring the activation of specific genes in the host plant. We studied expression patterns of nodule-expressed genes after infection with the root-knot nematode Meloidogyne incognita. Two regulators induced during nodule organogenesis, the early nodulin gene ENOD40 involved in primordium formation and the cell cycle gene CCS52a required for cell differentiation and endoreduplication, are expressed in galls of the host plant. Expression analysis of promoter-uidA fusions indicates an accumulation of CCS52a transcripts in giant cells undergoing endoreduplication, while ENOD40 expression is localized in surrounding cell layers. Transgenic plants overexpressing ENOD40 show a significantly higher number of galls. In addition, out of the 192 nodule-expressed genes tested, 38 genes were upregulated in nodules at least threefold compared with control roots, but only two genes, nodulin 26 and cyclin D3, were found to be induced in galls. Taken together, these results suggest that certain events, such as endoreduplication, cell-to-cell communication with vascular tissues, or water transport, might be common between giant cell formation and nodule development.

Animals↗

PubMed2000

Nematode Parasitism Genes.

The ability of nematodes to live on plant hosts involves multiple parasitism genes. The most pronounced morphological adaptations of nematodes for plant parasitism include a hollow, protrusible stylet (feeding spear) connected to three enlarged esophageal gland cells that express products that are secreted into plant tissues through the stylet. Reverse genetic and expressed sequence tag (EST) approaches are being used to discover the parasitism genes expressed in nematode esophageal gland cells. Some genes cloned from root-knot (Meloidogyne spp.) and cyst (Heterodera and Globodera spp.) nematodes have homologues reported in genomic analyses of Caenorhabditis elegans and animal-parasitic nematodes. To date, however, the candidate parasitism genes endogenous to the esophageal glands of plant nematodes (such as the ß-1,4-endoglucanases) have their greatest similarity to microbial genes, prompting speculation that genes for plant parasitism by nematodes may have been acquired by horizontal gene transfer.

functional genomics↗