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P Castagnone-Sereno

Publications and source records attributed to P Castagnone-Sereno.

14 recordsLinked to original sources
PubMed2006

Genetic variability and adaptive evolution in parthenogenetic root-knot nematodes.

Root-knot nematodes (RKN) of the genus Meloidogyne are biotrophic plant parasites of major agricultural importance, which exhibit very variable modes of reproduction, from classical amphimixis to mitotic parthenogenesis. This review focuses on those RKN species that reproduce exclusively by mitotic parthenogenesis (apomixis), in contrast to those that have meiotic/amphimitic events in their life cycle. Although populations of clonal organisms are often represented as being ecologically isolated and evolutionary inert, a considerable volume of literature provides evidence that asexual RKN are neither: they are widely distributed, extremely polyphagous, and amenable to selection and adaptive variation. The ancestors of the genus are unknown, but it is assumed that the parthenogenetic RKN have evolved from amphimictic species through hybridization and subsequent aneuploidization and polyploidization events. Molecular studies have indeed confirmed that the phylogenetic divergence between meiotic and mitotic RKN lineages occurred early, and have revealed an unexpected level of clonal diversity among populations within apomictic species. Laboratory experiments have shown that asexual RKN can rapidly adapt to new environmental constraints (eg host resistance), although with some fitness costs. Lastly, the molecular and chromosomal mechanisms that could contribute to genome plasticity leading to persistent genetic variation and adaptive evolution in apomictic RKN are discussed. It is concluded that RKN provide an excellent model system in which to study the dynamic nature and adaptive potential of clonal genomes.

Adaptation, Physiological↗
PubMed2001

Molecular cloning of a cDNA encoding an amphid-secreted putative avirulence protein from the root-knot nematode Meloidogyne incognita.

Amplified fragment length polymorphism fingerprinting of three pairs of Meloidogyne incognita near-isogenic lines (NILs) was used to identify markers differential between nematode genotypes avirulent or virulent against the tomato Mi resistance gene. One of these sequences, present only in the avirulent lines, was used as a probe to screen a cDNA library from second-stage juveniles (J2s) and allowed cloning of a cDNA encoding a secretory protein. The putative full-length cDNA, named map-1, encoded a 458 amino acid (aa) protein containing a predictive N-terminal secretion signal peptide. The MAP-1 sequence did not show any significant similarity to proteins deposited in databases. The internal part of the protein, however, was characterized by highly conserved repetitive motives of 58 or 13 aa. Reverse transcription polymerase chain reaction (RT-PCR) experiments confirmed that map-1 expression was different between avirulent and virulent NILs. In PCR reactions, map-1-related sequences were amplified only in nematode populations belonging to the three species against which the Mi gene confers resistance: M. arenaria, M. incognita, and M. javanica. Polyclonal antibodies raised against a synthetic peptide deduced from the MAP-1 sequence strongly labeled J2 amphidial secretions in immunofluorescence microscopy assays, suggesting that MAP-1 may be involved in the early steps of recognition between (resistant) plants and (avirulent) nematodes.

Amino Acid Sequence↗
PubMed2000

Identification of mariner-like elements from the root-knot nematode Meloidogyne spp.

The Meloidogyne species are agriculturally important pests widespread in the world. These polyphagous endoparasitic nematodes possess an astonishing ability to bypass the plant resistance genes in few generations. However, the genes and mechanisms involved in this molecular determinism are not yet known. Except cytogenetic and cytotaxonomic studies, few data are available concerning their genome. There is therefore an important need of molecular tools for genetic investigation of their virulence character and other aspects of host-pathogen interactions. In that respect, the presence of mariner-like-elements (MLEs) was assessed in these endoparasitic nematodes by a polymerase chain reaction (PCR) assay using degenerate primers designed from two conserved regions of the mariner transposase open reading frame (ORF). Four Meloidogyne species of the five tested revealed the presence of MLEs in their genome. Southern blot analysis indicated that sequences hybridizing to the mariner transposase-like PCR clones occur at a moderate to low copy number in the different Meloidogyne spp. genomes. The phylogenetic analysis show that the Meloidogyne MLEs may form new subfamilies of mariner. Moreover, five PCR clones were shown to possess a continuous ORF suggesting the presence of putative transposase-like coding regions.

Amino Acid Sequence↗
PubMed2000

Virulence and molecular diversity of parthenogenetic root-knot nematodes, Meloidogyne spp.

Root-knot nematodes (RKN) are sedentary endoparasites causing severe damage to a wide variety of crops, including tomato. Among them, the parthenogenetic species Meloidogyne arenaria, M. incognita and M. javanica are of particular economic importance. The genetic diversity and relationships of 17 populations belonging to these three major species, either avirulent or virulent against the tomato Mi resistance gene, were investigated in order to determine whether (a)virulence of the nematodes could be related to their molecular fingerprints. Genomic polymorphisms between populations were assessed by using amplified fragment length polymorphism (AFLP) markers, and data were treated by means of a multiple correspondence analysis. A total of 1550 polymorphic amplified DNA fragments were identified and used to compute the relationships between the populations. As expected, the three RKN species were clearly distributed into distinct groups, but combination of data for virulence phenotypes and DNA markers showed that clustering of populations was not associated with their (a)virulence against the tomato Mi resistance gene. Such a lack of correlation indicates that most of the observed DNA polymorphism is independent of virulence, which is presumably under host selection. This result demonstrates that virulent populations do not share a common origin, and strongly suggests that they might have appeared late after the establishment of these clonal lineages, as the result of independent mutational events.

Animals↗
PubMed2000

Cloning and characterization of an extremely conserved satellite DNA family from the root-knot nematode Meloidogyne arenaria.

A new satellite DNA family, named pMaE, has been cloned from the genome of the phytoparasitic nematode, Meloidogyne arenaria (Nematoda: Tylenchida). It is represented as tandemly repeated sequences with a monomeric unit of 172 bp. The monomers are present at approximately 15700 copies per haploid genome, and represent about 5.3% of the total genomic DNA. Twenty-seven independent monomers have been cloned and sequenced. The deduced consensus sequence is 70.9% A + T rich, with frequent stretches of A and (or) T. Several direct or inverted sub-repeats are present in the sequence, which may allow the formation of a dyad structure, suggesting some potential role of this repetitive sequence in heterochromatin condensation. The monomers are very homogeneous in sequence, showing on average 1.8% divergence from their consensus sequence. Moreover, Southern blot experiments and sequence analysis of homologous monomers from the genome of geographically distinct M. arenaria populations have shown that this satellite DNA is uniformly distributed and highly conserved within the species. Therefore, it is hypothesized that this unusually low level of variability, either within the genome of a given population or between populations, could be achieved as the result of some highly effective homogenization mechanism acting upon the nematode genome.

Animals↗
PubMed1998

Unusual and strongly structured sequence variation in a complex satellite DNA family from the nematode Meloidogyne chitwoodi.

An AluI satellite DNA family has been isolated in the genome of the root-knot nematode Meloidogyne chitwoodi. This repeated sequence was shown to be present at approximately 11,400 copies per haploid genome, and represents about 3.5% of the total genomic DNA. Nineteen monomers were cloned and sequenced. Their length ranged from 142 to 180 bp, and their A + T content was high (from 65.7 to 79.1%), with frequent runs of As and Ts. An unexpected heterogeneity in primary structure was observed between monomers, and multiple alignment analysis showed that the 19 repeats could be unambiguously clustered in six subfamilies. A consensus sequence has been deduced for each subfamily, within which the number of positions conserved is very high, ranging from 86.7% to 98.6%. Even though blocks of conserved regions could be observed, multiple alignment of the six consensus sequences did not enable the establishment of a general unambiguous consensus sequence. Screening of the six consensus sequences for evidence of internal repeated subunits revealed a 6-bp motif (AAATTT), present in both direct and inverted orientation. This motif was found up to nine times in the consensus sequences, also with the occurrence of degenerated subrepeats. Along with the meiotic parthenogenetic mode of reproduction of this nematode, such structural features may argue for the evolution of this satellite DNA family either (1) from a common ancestral sequence by amplification followed by mechanisms of sequence divergence, or (2) through independent mutations of the ancestral sequence in isolated amphimictic nematode populations and subsequent hybridization events. Overall, our results suggest the ancient origin of this satellite DNA family, and may reflect for M. chitwoodi a phylogenetic position close to the ancestral amphimictic forms of root-knot nematodes.

Animals↗
PubMed1998

High-resolution DNA fingerprinting of parthenogenetic root-knot nematodes using AFLP analysis.

Amplified fragment length polymorphism (AFLP) analysis has been used to characterize 15 root-knot nematode populations belonging to the three parthenogenetic species Meloidogyne arenaria, M. incognita and M. javanica. Sixteen primer combinations were used to generate AFLP patterns, with a total number of amplified fragments ranging from 872 to 1087, depending on the population tested. Two kinds of polymorphic DNA fragments could be distinguished: bands amplified in a single genotype, and bands polymorphic between genotypes (i.e. amplified in not all but at least two genotypes). Based on presence/absence of amplified bands and pairwise similarity values, all the populations tested were clustered according to their specific status. Significant intraspecific variation was revealed by AFLP, with DNA fragments polymorphic among populations within each of the three species tested. M. arenaria appeared as the most variable species, while M. javanica was the least polymorphic. Within each specific cluster, no general correlation could be found between genomic similarity and geographical origin of the populations. The results reported here showed the ability of the AFLP procedure to generate markers useful for genetic analysis in root-knot nematodes.

Animals↗
PubMed1998

A new AluI satellite DNA in the root-knot nematode Meloidogyne fallax: relationships with satellites from the sympatric species M. hapla and M. chitwoodi.

A highly abundant satellite DNA comprising 20% of the Meloidogyne fallax (Nematoda, Tylenchida) genome was cloned and sequenced. The satellite monomer is 173 bp long and has a high A + T content of 72.3%, with frequent runs of A's and T's. The sequence variability of the monomers is 2.7%, mainly due to random distribution of single-point mutations. A search for evidence of internal repeated subunits in the monomer sequence revealed a 6-bp motif (AAATTT) for which five degenerated repeats, differing by just a single base pair, could be identified. Pairwise comparison of the M. fallax satellite with those from the sympatric species Meloidogyne chitwoodi and Meloidogyne hapla revealed a high sequence similarity (68.39%) with one satellite DNA subfamily in M. chitwoodi, which indicated an unexpected close relationship between them. Given the high copy number and the extreme sequence homogeneity among monomeric units, it may be assumed that the satellite DNA of M. fallax could have evolved through some recent and extensive amplification burst in the nematode genome. In this case, its relatively short life would not yet have allowed the accumulation of random mutations in independent amplified repeats. Considering the morphological resemblance between the two species and their ability to produce interspecific fertile hybrids under controlled conditions, these results indicate that M. fallax may share a common ancestor with M. chitwoodi, from which it could have diverged recently. All these data suggest that M. fallax could be the result of a recent speciation process and show that Meloidogyne satellite DNAs may be of interest to resolve phylogenetic relationships among closely related species from this genus.

Animals↗
PubMed1997

Satellite DNA sequences as taxonomic markers in nematodes of agronomic interest.

The success of alternative crop protection practices against plant-parasitic nematodes using host resistance genes depends fundamentally upon identification of the species and pathotypes effectively controlled by these genes. In the same way, biological control of insects by entomopathogenic nematodes will work only if the nematode strains used are indeed active against the pests to be eliminated. For these applications, the accurate interspecific and/or intraspecific identification of nematodes is thus of outstanding importance. Here, Eric Grenier, Philippe Castagnone-Sereno and Pierre Abad discuss the recent use of satellite DNA sequences in nematode taxonomic diagnostics.

Journal Article↗
PubMed1995

Satellite DNA as a target for PCR-specific detection of the plant-parasitic nematode Meloidogyne hapla.

The polymerase chain reaction was evaluated for its ability to amplify DNA sequences specific for the root-knot nematode Meloidogyne hapla, using oligonucleotides whose sequence was deduced from the satellite DNA previously cloned in this species as primers. As expected, ladder patterns of monomers and multimers of an approximate 150-170-bp repeat were amplified from purified genomic DNA of all the M. hapla isolates studied, while no amplification was detected with the five other Meloidogyne species tested. Moreover, the satellite DNA nature of the amplification products was confirmed through Southern-blot hybridization with the previously cloned monomeric unit. In further experiments, DNA was extracted from single females, males, juveniles, or eggs according to a simple procedure, and used as a template in PCR assays. Amplification products were obtained, whose electrophoretic patterns were always very similar to those from M. hapla genomic DNA, thus demonstrating the high sensitivity of the method. This satellite DNA-based strategy can be exploited to develop species-specific primer sets for use on a routine basis as a diagnostic tool for unambiguous nematode identification procedures.

Animals↗
PubMed1994

Cloning and characterization of two satellite DNAs in the low-C-value genome of the nematode Meloidogyne spp.

Two highly reiterated StyI satellite DNAs have been cloned from two nematode species: one from Meloidogyne hapla and another from M. incognita. The monomeric units of these two satellites have a repeat length of 169 and 295 bp, respectively. These StyI repeated element families constitute 5% of the M. hapla and 2.5% of the M. incognita haploid genomes. The A + T content is elevated in both families (i.e., 68% and 77%, respectively). Nucleotide methylation and transcriptional activity are negative. No similarity was found between the two satellites, nor to other known highly repetitive elements. These StyI satellite DNAs are quite homogenous in sequence, showing on average 3% and 3.5% divergence from their respective calculated consensus sequence. An internal subrepeating unit of about 11 bp is observed in the StyI satellite monomer sequences of M. hapla, suggesting that it could have evolved from a shorter sequence. Because of the small size of the Meloidogyne genome (51 Mb) and the abundance of repeated sequences, this genus approaches a limit in terms of coding fraction.

Animals↗
PubMed1994

Genetic polymorphism between and within Meloidogyne species detected with RAPD markers.

Genetic analyses were conducted on root-knot nematode populations belonging to the four major species of the genus Meloidogyne and originating from many countries throughout the world. Discrete genetic markers used in this study were random genomic DNA sequences amplified by the polymerase chain reaction (RAPD). Primers of 17-30 nucleotides with 30-55% G + C content were tested. Five of them generated a total of 74 scorable markers that provided reliable polymorphisms both between and within species. Using RAPD patterns alone or in combination, all the Meloidogyne species and populations studied could be unambiguously discriminated. Based on the presence or absence of bands, maximum-parsimony analysis of the data resulted in clustering of species and populations congruent with previous isoenzymatic and molecular data. The resulting tree confirmed the early divergence of M. hapla from the other species and also that M. arenaria is closer to M. javanica than it is to M. incognita. The boot-strap analysis significantly supported most of the specific branching observed in the topology but did not identify the three M. arenaria populations as a monophyletic group.

Animals↗
PubMed1991

Sequences homologous to Tc(s) transposable elements of Caenorhabditis elegans are widely distributed in the phylum nematoda.

To have a better understanding of the evolutionary history of mobile elements within the nematodes, we examined the distribution and the conservation of homologues to transposable elements from Caenorhabditis elegans (Tc1, Tc2, Tc3, Tc4, Tc5, and FB1) in 19 nematode species belonging to the class Secernentea. Our results show that Tc1 elements display a distribution restricted to the family Rhabditidae with poor conservation. The Tc2 and FB1 homologous elements have the same patchy distribution within the Rhabditidae. They were only found in Caenorhabditis and in Teratorhabditis. The Tc3 element is widely distributed among nematode species. Tc3 homologous elements are present in the majority of the Rhabditidae but also in two genera within the family Panagrolaimidae, and in Bursaphelenchus, which belongs to the order Aphelenchida. Tc4 and Tc5 homologues show the most limited distribution of all tested elements, being strictly limited to C. elegans. These data indicate that in some cases, the distribution of transposable elements in the nematode cannot be explained by strict vertical transmission. The distribution of Tc3, Tc4, and Tc5 suggests that horizontal transmission may have occurred between reproductively isolated species during their evolutionary history.

Animals↗