RÉSUMÉ
Oak gall wasps have evolved strategies to manipulate the developmental pathways of their host to induce gall formation. This provides shelter and nutrients for the developing larva. Galls are entirely host tissue; however, the initiation, development, and physical appearance are controlled by the inducer. The underlying molecular mechanisms of gall formation, by which one or a small number of cells are reprogrammed and commit to a novel developmental path, are poorly understood. In this study, we sought a deeper insight into the molecular underpinnings of this process. Oak gall wasps have two generations each year, one sexual, and one asexual. Galls formed by these two generations exhibit a markedly different appearance. We sequenced transcriptomes of both the asexual and sexual generations of Neuroterus quercusbaccarum and Neuroterus numismalis. We then deployed Nanopore sequencing to generate long-read sequences to test the hypothesis that gall wasps introduce DNA insertions to determine gall development. We detected potential genome rearrangements but did not uncover any non-host DNA insertions. Transcriptome analysis revealed that transcriptomes of the sexual generations of distinct species of wasp are more similar than inter-generational comparisons from the same species of wasp. Our results highlight the intricate interplay between the host leaves and gall development, suggesting that season and requirements of the gall structure play a larger role than species in controlling gall development and structure.
Sujet(s)
Tumeurs végétales , Quercus , Transcriptome , Guêpes , Animaux , Guêpes/physiologie , Guêpes/génétique , Tumeurs végétales/parasitologie , Tumeurs végétales/génétique , Quercus/génétique , Quercus/parasitologie , Transcriptome/génétique , Reproduction asexuée/génétique , Interactions hôte-parasite/génétique , Analyse de profil d'expression de gènesRÉSUMÉ
* The transcriptome of an organism is its set of gene transcripts (mRNAs) at a defined spatial and temporal locus. Because gene expression is affected markedly by environmental and developmental perturbations, it is widely assumed that transcriptome divergence among taxa represents adaptive phenotypic selection. This assumption has been challenged by neutral theories which propose that stochastic processes drive transcriptome evolution. * To test for evidence of neutral transcriptome evolution in plants, we quantified 18 494 gene transcripts in nonsenescent leaves of 14 taxa of Brassicaceae using robust cross-species transcriptomics which includes a two-step physical and in silico-based normalization procedure based on DNA similarity among taxa. * Transcriptome divergence correlates positively with evolutionary distance between taxa and with variation in gene expression among samples. Results are similar for pseudogenes and chloroplast genes evolving at different rates. Remarkably, variation in transcript abundance among root-cell samples correlates positively with transcriptome divergence among root tissues and among taxa. * Because neutral processes affect transcriptome evolution in plants, many differences in gene expression among or within taxa may be nonfunctional, reflecting ancestral plasticity and founder effects. Appropriate null models are required when comparing transcriptomes in space and time.
Sujet(s)
Arabidopsis/génétique , Brassicaceae/génétique , Évolution moléculaire , Analyse de profil d'expression de gènes , Gènes de plante , Dérive génétique , Protéines d'Arabidopsis/génétique , Sondes d'ADN , Expression des gènes , Variation génétique , Génome de chloroplaste , Protéines à homéodomaine/génétique , Modèles génétiques , Phylogenèse , Racines de plante/génétique , Pseudogènes , ARN messager/génétique , Processus stochastiques , Facteurs de transcription/génétiqueRÉSUMÉ
Many gram-negative bacteria employ N-acylhomoserine lactones (AHL) to regulate diverse physiological processes in concert with cell population density (quorum sensing [QS]). In the plant pathogen Erwinia carotovora, the AHL synthesized via the carI/expI genes are responsible for regulating the production of secreted plant cell wall-degrading exoenzymes and the antibiotic carbapen-3-em carboxylic acid. We have previously shown that targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in planta of the cognate AHL signaling molecules N-(3-oxohexanoyl)-L-homoserine lactone (3-oxo-C6-HSL) and N-hexanoylhomoserine lactone (C6-HSL), which in turn, were able to complement a carI-QS mutant. In the present study, we demonstrate that transgenic potato plants containing the yenI gene are also able to express AHL and that the presence and level of these AHL in the plant increases susceptibility to infection by E. carotovora. Susceptibility is further affected by both the bacterial level and the plant tissue under investigation.
Sujet(s)
Carboxylic ester hydrolases/métabolisme , Pectobacterium carotovorum/pathogénicité , Solanum tuberosum/génétique , Chromatographie sur couche mince , Numération de colonies microbiennes , Régulation de l'expression des gènes bactériens , Pectobacterium carotovorum/génétique , Maladies des plantes/microbiologie , Tubercules/génétique , Tubercules/croissance et développement , Végétaux génétiquement modifiés , Solanum tuberosum/croissance et développement , Solanum tuberosum/microbiologieRÉSUMÉ
Many plant-associated microbes use secreted autoinducer molecules, including N-acylhomoserine lactones (AHLs), to regulate diverse behaviours in association with their population density (quorum sensing). Often, these responses are affected by environmental conditions, including the presence of other AHL-producing bacterial species. In addition, plant-derived metabolites, including products that arise as a direct result of the bacterial infection, may profoundly influence AHL-regulated behaviours. These plant products can interact directly and indirectly with the quorum-sensing network and can profoundly affect the quorum-sensing behaviour. Local conditions on a microscopic scale may affect signal molecule longevity, stability and accumulation, and this could be used to give information in addition to cell density. Furthermore, in many Gram-negative bacteria, AHL signalling is subservient to an additional two-component signalling system dependent upon homologues of GacS and GacA. The signal(s) to which GacS responds are not known, but recent research suggests that a self-produced ligand may be being detected. This review will focus on two well-studied examples of AHL-regulated plant-associated behaviour, Erwinia carotovora and Agrobacterium tumefaciens, to illustrate the complexity of such signalling networks.
Sujet(s)
Agrobacterium tumefaciens/métabolisme , Erwinia/métabolisme , Plantes/microbiologie , Transduction du signal/physiologie , Agrobacterium tumefaciens/composition chimique , Erwinia/composition chimique , Plantes/composition chimique , Plantes/métabolismeRÉSUMÉ
The Agrobacterium tumefaciens C58 genome contains three putative N-acyl homoserine lactone (acyl-HSL) hydrolases, which are closely related to the lactonase AiiA of Bacillus. When expressed in Escherichia coli, two of the putative acyl-HSL hydrolases, AttM and AiiB, conferred the ability to degrade acyl-HSLs on the host. In Erwinia strain 6276, the lactonases reduced the endogenous acyl-HSL level and the bacterial virulence in planta.
Sujet(s)
4-Butyrolactone/analogues et dérivés , Agrobacterium tumefaciens/génétique , Carboxylic ester hydrolases/génétique , Plasmides inducteurs de tumeurs de plantes , 4-Butyrolactone/métabolisme , Agrobacterium tumefaciens/enzymologie , Séquence d'acides aminés , Hydrolases/génétique , Données de séquences moléculairesRÉSUMÉ
The hormone ethylene regulates many aspects of plant growth and development, including fruit ripening. In transgenic tomato (Lycopersicon esculentum) plants, antisense inhibition of ethylene biosynthetic genes results in inhibited or delayed ripening. The dominant tomato mutant, Never-ripe (Nr), is insensitive to ethylene and fruit fail to ripen. The Nr phenotype results from mutation of the ethylene receptor encoded by the NR gene, such that it can no longer bind the hormone. NR has homology to the Arabidopsis ethylene receptors. Studies on ethylene perception in Arabidopsis have demonstrated that receptors operate by a "receptor inhibition" mode of action, in which they actively repress ethylene responses in the absence of the hormone, and are inactive when bound to ethylene. In ripening tomato fruit, expression of NR is highly regulated, increasing in expression at the onset of ripening, coincident with increased ethylene production. This expression suggests a requirement for the NR gene product during the ripening process, and implies that ethylene signaling via the tomato NR receptor might not operate by receptor inhibition. We used antisense inhibition to investigate the role of NR in ripening tomato fruit and determine its mode of action. We demonstrate restoration of normal ripening in Nr fruit by inhibition of the mutant Nr gene, indicating that this receptor is not required for normal ripening, and confirming receptor inhibition as the mode of action of the NR protein.
Sujet(s)
Protéines végétales/génétique , Protéines végétales/métabolisme , ARN antisens/pharmacologie , Récepteurs de surface cellulaire/métabolisme , Solanum lycopersicum/physiologie , Technique de Northern , Régulation négative , Solanum lycopersicum/génétique , Solanum lycopersicum/métabolisme , Mutation , Phénotype , Protéines végétales/antagonistes et inhibiteurs , Végétaux génétiquement modifiés , ARN messager/analyse , ARN des plantes/analyse , Transduction du signalRÉSUMÉ
N-acylhomoserine lactones (AHLs) play a critical role in plant/microbe interactions. The AHL, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), induces exoenzymes that degrade the plant cell wall by the pathogenic bacterium Erwinia carotovora. Conversely, the antifungal activity of the biocontrol bacterium Pseudomonas aureofaciens 30-84 is due (at least in part) to phenazine antibiotics whose synthesis is regulated by N-hexanoylhomoserine lactone (HHL). Targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in plants of the cognate AHL signaling molecules (OHHL and HHL). The AHLs produced by the transgenic plants were sufficient to induce target gene expression in several recombinant bacterial AHL biosensors and to restore biocontrol activity to an HHL-deficient P. aureofaciens strain. In addition, pathogenicity was restored to an E. carotovora strain rendered avirulent as a consequence of a mutation in the OHHL synthase gene, carI. The ability to generate bacterial quorum-sensing signaling molecules in the plant offers novel opportunities for disease control and for manipulating plant/microbe interactions.
Sujet(s)
Génie génétique , Lactones/métabolisme , Pectobacterium carotovorum/métabolisme , Végétaux génétiquement modifiés/microbiologie , Protéines bactériennes/génétique , Transduction du signal , Transactivateurs/génétique , Yersinia enterocolitica/génétiqueRÉSUMÉ
Using the Arabidopsis ethylene receptor ETR1 as a probe, we have isolated a tomato homologue (tETR) from a ripening cDNA library. The predicted amino acid sequence is 70% identical to ETR1 and homologous to a variety of bacterial two component response regulators over the histidine kinase domain. Sequencing of four separate cDNAs indicates that tETR lacks the carboxyl terminal response domain and is identical to that encoded by the tomato Never ripe gene. Ribonuclease protection showed tETR mRNA was undetectable in unripe fruit or pre-senescent flowers, increased in abundance during the early stages of ripening, flower senescence, and in abscission zones, and was greatly reduced in fruit of ripening mutants deficient in ethylene synthesis or response. These results suggest that changes in ethylene sensitivity are mediated by modulation of receptor levels during development.
Sujet(s)
Régulation de l'expression des gènes végétaux , Protéines végétales/biosynthèse , Pousses de plante/croissance et développement , Récepteurs de surface cellulaire/biosynthèse , Solanum lycopersicum/croissance et développement , Séquence d'acides aminés , Séquence nucléotidique , Éthylènes/métabolisme , Solanum lycopersicum/génétique , Données de séquences moléculaires , Protéines végétales/génétique , ARN messager/biosynthèse , ARN des plantes/biosynthèse , Récepteurs de surface cellulaire/génétique , Similitude de séquences d'acides aminés , Distribution tissulaireSujet(s)
Alkyl et aryl transferases , Protéines de liaison à l'ADN , Épistasie , Régulation de l'expression des gènes végétaux , Gènes de plante , Végétaux génétiquement modifiés/génétique , ARN antisens/génétique , Solanum lycopersicum/génétique , Amino-acid oxidoreductases/biosynthèse , Amino-acid oxidoreductases/génétique , Amino-acid oxidoreductases/physiologie , Carboxylic ester hydrolases/biosynthèse , Carboxylic ester hydrolases/génétique , Carboxylic ester hydrolases/physiologie , Paroi cellulaire/métabolisme , Induction enzymatique , Éthylènes/métabolisme , Geranylgeranyl-diphosphate geranylgeranyltransferase , Lyases/biosynthèse , Lyases/génétique , Lyases/physiologie , Solanum lycopersicum/croissance et développement , Protéines végétales/biosynthèse , Protéines végétales/génétique , Protéines végétales/physiologie , Polygalacturonase/biosynthèse , Polygalacturonase/génétique , Polygalacturonase/physiologie , Transferases/biosynthèse , Transferases/génétique , Transferases/physiologieRÉSUMÉ
The nucleotide sequence and derived amino acid sequence were determined for a full-length version of the tomato cDNA clone, pTOM75, the mRNA for which has previously been shown to accumulate in roots, ripening fruit and senescing leaves. Computer analysis of the predicted protein product, which we have named tomato ripening-associated membrane protein (TRAMP) indicates strong homology to known transmembrane channel proteins from other organisms. Northern analysis showed that this gene was induced by waterstress and that this induction was unaffected in an ABA-deficient genetic background.
Sujet(s)
Protéines bactériennes/génétique , ADN complémentaire/génétique , Immunophilines , Protéines membranaires/génétique , Peptidylpropyl isomerase , Protéines végétales , Légumes/génétique , Séquence d'acides aminés , Séquence nucléotidique , Technique de Northern , ADN complémentaire/biosynthèse , Expression des gènes , Protéines membranaires/biosynthèse , Données de séquences moléculaires , ARN/analyse , ARN/biosynthèse , Similitude de séquences d'acides aminésRÉSUMÉ
Tomato ripening is an excellent system for studying control of gene expression in plants. A multiplicity of well-defined biochemical and genetic changes occur in a precise sequence, regulated by a gaseous hormone. The generation of targeted mutations using sense and antisense genes provides a means of manipulating endogenous gene expression, both for answering fundamental questions and for crop improvement.
Sujet(s)
Légumes/génétique , Expression des gènesRÉSUMÉ
Tomatoes (Lycopersicon esculentum Mill cv. Ailsa Craig) were transformed with a gene construct having 244 bp of the 5' end of a polygalacturonase (PG) cDNA, coding for a 71 amino acid N-terminal extension to the mature protein, fused to 1320 bp of a pectin-esterase (PE) cDNA encoding the full sequence of the mature PE protein. This chimaeric gene was inserted in a sense orientation between a CaMV 35S promoter and terminator for constitutive expression. In transformed tomato plants expression of the endogenous PG and PE genes in the fruit was inhibited; there was little or no observable PG and PE mRNA and a substantial reduction in the level of PG and PE enzyme activity. The transgene was expressed in the leaves of the transformed plants as demonstrated by the accumulation of mRNA, but no protein product could be identified. However, no transgene mRNA or protein were observed in the transgenic fruit. The paper represents the first report of the down-regulation of two non-homologous endogenous genes using a single gene construct. A sense gene construct was responsible for these effects. These findings are discussed in relation to possible mechanisms of action of co-suppression.
Sujet(s)
Régulation de l'expression des gènes , Gènes de plante , Légumes/génétique , Technique de Northern , Technique de Southern , Carboxylic ester hydrolases/biosynthèse , Carboxylic ester hydrolases/génétique , Clonage moléculaire , Régulation négative , Électrophorèse sur gel de polyacrylamide , Polygalacturonase/biosynthèse , Polygalacturonase/génétique , Protéines de fusion recombinantes/génétique , Transformation génétique , Légumes/enzymologieRÉSUMÉ
A tomato phytoene synthase gene, Psy1, has recently been isolated as the clone GTOM5 and shown by sequence identity to be the gene from which the major fruit-ripening cDNA clone TOM5 was derived. Sequence analysis of transcripts from two allelic yellow-fruited tomato mutants, mapped to chromosome 3, has shown the lack of carotenoids in fruit of these mutants to be due to the production of aberrant TOM5 transcripts which are unlikely to encode a functional phytoene synthase enzyme. In one mutant (yellow flesh) the aberrant transcript contained a sequence that, by its strong hybridization to a wide size range of genomic fragments, appeared to be repeated many times within the genome. Southern and PCR analysis of the phytoene synthase genes in the mutant revealed restriction fragment length polymorphisms, suggesting that the production of altered mRNAs was associated with specific genomic rearrangements. Constitutive over-expression of a TOM5 cDNA clone in transgenic mutant plants restored synthesis of the carotenoid lycopene in ripening fruit and also led to unscheduled pigment production in other cell types. In some mutant plants transformed with the TOM5 cDNA construct, inhibition of carotenoid production in immature green fruit, leaves and flowers was observed, due to the phenomenon of co-suppression, indicating that different insertion events with the same gene construct can lead to overexpression or co-suppression in transgenic plants. Green organs of these plants were susceptible to photobleaching, due to the lack of carotenoids. These results suggest the existence of separate Psy genes for carotenoid synthesis in green organs.
Sujet(s)
Alkyl et aryl transferases , Fruit/génétique , Ligases/génétique , Pigmentation/génétique , Suppression génétique , Séquence nucléotidique , Caroténoïdes/analyse , Chlorophylle/analyse , Cartographie chromosomique , Test de complémentation , Génome , Geranylgeranyl-diphosphate geranylgeranyltransferase , Ligases/biosynthèse , Données de séquences moléculaires , Végétaux génétiquement modifiés/génétique , ARN messager/génétique , Protéines recombinantes/biosynthèse , Analyse de séquence d'ADN , Similitude de séquences d'acides nucléiques , Distribution tissulaire , Transformation génétiqueSujet(s)
Dysgerminome/diagnostic , Dysgénésie gonadique 46, XY/diagnostic , Dysgénésie gonadique/diagnostic , Adolescent , Appendicite/complications , Appendicite/chirurgie , Dysgerminome/complications , Dysgerminome/chirurgie , Femelle , Dysgénésie gonadique 46, XY/complications , Dysgénésie gonadique 46, XY/chirurgie , Humains , CaryotypageRÉSUMÉ
This study was designed to determine whether immunohistochemical stains for tumour-associated markers may be useful in the detection and differential diagnosis of premalignant and malignant lesions of the cervix. The expression of four markers detected by monoclonal antibodies, human milk fat globule 1 and 2 (HMFG-1 and 2), Ca1 and anti-carcinoembryonic antigen (anti-CEA) on conventional histological sections of various cervical lesions has been investigated. None of these markers was specific for neoplastic lesions of the cervix and all four markers were expressed by metaplastic as well as neoplastic cells, and it was concluded that their application in the histopathological examination of the cervix is limited.
Sujet(s)
Tumeurs du col de l'utérus/diagnostic , Anticorps/analyse , Anticorps monoclonaux , Antigène carcinoembryonnaire/analyse , Col de l'utérus/anatomopathologie , Femelle , Humains , Techniques immunoenzymatiques , Protéines membranaires/analyse , Métaplasie/diagnostic , Mucine-1 , Dysplasie du col utérin/diagnosticRÉSUMÉ
A case of herpes simplex genitalis producing radiculomyelopathy with urinary retention is reported. The patient was treated with adenosine arabinoside intravenously and made a complete recovery over 4 weeks. Although herpes simplex genitalis is common, neurological sequelae, particularly cord involvement, are distinctly rare. It should, nevertheless, be considered in the differential diagnosis of urinary retention, with or without long-tract signs, in young patients.