34 research outputs found
Genome structure and pathogenicity of the fungal wheat pathogen Mycosphaerella graminicola
The phytopathogenic fungus Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn (asexual stage: Zymoseptoria tritici (Desm.) Quaedvlieg & Crous) causes septoria tritici leaf blotch (STB) in wheat and is one of the most important diseases of this crop worldwide. However, STB control, mainly based on the use of resistant cultivars and fungicides, is significantly hampered by the limited understanding of the genetic and biochemical bases of pathogenicity, and mechanisms of infection and resistance in the host. M. graminicola has a very active sexual cycle under field conditions, which is an important driver of STB epidemics. Moreover, it results in high genetic diversity of field populations that causes a major challenge for the development and sustainable management of resistant cultivars and the discovery of new antifungal compounds. Understanding the role of the sexual and asexual life cycles on genome composition of this versatile pathogen and its infection strategy is crucial in order to develop novel control methods. Chapter 1 is an introduction to the biology and pathogenicity of M. graminicola. In addition, it shortly describes the impact of improved and novel technologies on the speed, scope and scale of comparative genomics research. Chapter 2 provides detailed genetic analyses of two M. graminicola mapping populations, using mainly DArT markers, and the analysis of the meiotic transmission of unequal chromosome numbers. Polymorphisms in chromosome length and number were frequently observed in progeny isolates, of which 15â20% lacked one or more chromosomes despite their presence in one or both parents, but these had no apparent effect on sexual and pathogenic fitness. M. graminicola has up to eight so called dispensable chromosomes that can be easily lost - collectively called the dispensome - which is, so far, the highest number of dispensable chromosomes reported in filamentous fungi. They represent small-sized chromosomes and make up 38% of the chromosome complement of this pathogen. Much of the observed genome plasticity is generated during meiosis and could explain the high adaptability of M. graminicola in the field. The generated linkage map was crucial for finishing the M. graminicola genome sequence. Chapter 3 describes the M. graminicola genome sequence with highlights on genome structure and organization including the eight dispensable chromosomes. The genome comprises a core set of 13 chromosomes and a dispensome, consisting of eight chromosomes that are distinct from the core chromosomes in structure, gene and repeat content. The dispensome contains a higher frequency of transposons and the genes have a different codon use. Most of the genes present one the dispensome are also present on the core chromosomes but little synteny is observed neither between the M. graminicola dispensome and the core chromosomes nor with the chromosomes of other related Dothideomycetes. The dispensome likely originates from ancient horizontal transfer(s) from (an) unknown donor(s). Chapter 4 shows a global analysis of proteins secreted by M. graminicola in apoplastic fluids during infection. It focuses mainly on fungal proteins secreted in a compatible interaction. The study showed that many of the annotated secreted proteins have putative functions in fungal pathogenicity, such as cell wall degrading enzymes and proteases, but the function of a substantial number of the identified proteins is unknown. During compatible interactions proteins are primarily secreted during the later stages. However, many pathogenesis-related host proteins, such as PR-2, PR-3 and PR-9, accumulated earlier and at higher concentrations during incompatible interactions, indicating that fungal effectors are recognized by resistant plants and trigger resistant gene-mediated defence responses, though without a visible hypersensitive response. Chapter 5 further details the initial identification and characterization of necrosis-inducing proteins that are produced in culture filtrates (CFs) of M. graminicola. The necrosis-inducing activity of CFs is light dependent and inactivated by proteinase K and heat treatment (100ï°C). This is reminiscent of the necrosis-inducing properties of host selective toxins of other Dothideomycete pathogens such as Stagonospora nodorum and Pyrenophora tritici-repentis. Subsequent purifications of CFs and mass spectrometry identified several candidate proteins with necrosis-inducing activity. Heterologous expression of the two most prominent proteins in Pichia pastoris produced sufficient quantities for infiltration assays in a panel of wheat cultivars that showed differential responses, suggesting specific recognition. Chapter 6 provides a general discussion of the thesis and puts the results obtained in a broader perspective with a focus on the genome structure of M. graminicola and its function. In addition, aspects of the hemi-biotrophic lifestyle, the relevance of secreted proteins for the wheat-M. graminicola pathosystem in relation to gene-for-gene models and the potential implications for resistance breeding strategies are discussed. </p
Ga and GĂ Proteins Regulate the Cyclic AMP Pathway That Is Required for Development and Pathogenicity of the Phytopathogen Mycosphaerella graminicola
We identified and functionally characterized genes encoding three G alpha proteins and one G beta protein in the dimorphic fungal wheat pathogen Mycosphaerella graminicola, which we designated MgGpa1, MgGpa2, MgGpa3, and MgGpb1, respectively. Sequence comparisons and phylogenetic analyses showed that MgGPA1 and MgGPA3 are most related to the mammalian G alpha(i) and G alpha(s) families, respectively, whereas MgGPA2 is not related to either of these families. On potato dextrose agar (PDA) and in yeast glucose broth (YGB), MgGpa1 mutants produced significantly longer spores than those of the wild type (WT), and these developed into unique fluffy mycelia in the latter medium, indicating that this gene negatively controls filamentation. MgGpa3 mutants showed more pronounced yeast-like growth accompanied with hampered filamentation and secreted a dark-brown pigment into YGB. Germ tubes emerging from spores of MgGpb1 mutants were wavy on water agar and showed a nested type of growth on PDA that was due to hampered filamentation, numerous cell fusions, and increased anastomosis. Intracellular cyclic AMP (cAMP) levels of MgGpb1 and MgGpa3 mutants were decreased, indicating that both genes positively regulate the cAMP pathway, which was confirmed because the WT phenotype was restored by adding cAMP to these mutant cultures. The cAMP levels in MgGpa1 mutants and the WT were not significantly different, suggesting that this gene might be dispensable for cAMP regulation. In planta assays showed that mutants of MgGpa1, MgGpa3, and MgGpb1 are strongly reduced in pathogenicity. We concluded that the heterotrimeric G proteins encoded by MgGpa3 and MgGpb1 regulate the cAMP pathway that is required for development and pathogenicity in M. graminicola
Les osteomes des sinus de la face
Introduction : Le but de notre travail est prĂ©ciser le profil Ă©pidĂ©mio-clinique de cette pathologie, lâapport de lâimagerie dans le diagnostic, et discuter les modalitĂ©s de lâexĂ©rĂšse chirurgicale et lâapport de la voie endoscopique.Patients et mĂ©thode : il sâagit dâune Ă©tude rĂ©trospective de 18 patients porteurs dâostĂ©omes des sinus paranasaux opĂ©rĂ©s entre 1993 Ă 2010. Ont Ă©tĂ© exclus les patients non opĂ©rĂ©s et les malades perdus de vue.RĂ©sultats : il sâagit de 18 patients porteurs dâun ostĂ©ome symptomatique des sinus de la face, dâĂąge moyen 40 ans, sex ratio 0,38. La localisation la plus frĂ©quente Ă©tait le sinus frontal dans 55.5% des cas. Le traitement chirurgical Ă©tait de mise pour les patients symptomatiques. La voie endonasale Ă©tait indiquĂ©e dans 6 cas.la rĂ©cidive a intĂ©ressĂ© deux patients (11%) ayant un ostĂ©ome frontal et fronto-ethmoĂŻdal. Pour le reste des malades lâĂ©volution Ă©tait favorable avec un recul moyen de 36 mois.Conclusion : LâostĂ©ome des sinus paranasaux reste longtemps asymptomatique mais peut se compliquer par extension orbitaire ou cĂ©rĂ©brale. Lâabord endonasal a permis dâamĂ©liorer la prise en charge.Mots clĂ©s : OstĂ©ome, sinus de la face, tomodensitomĂ©trie, chirurgie, voie endonasaleObjective : Lymph node infection is the most frequent localization of extrapulmonary tuberculosis. The treatment does not make general agreement. The aim of this study is to specify, from a review of the literature, the different ways of antimicrobial treatment and the indications of surgery.Patients and methods : il is about a retrospective study including 18 patients with paranasal sinus osteomas operated between 1993 and 2010. Were excluded unoperated and lost patients.Results : in this group of 18 patients with symptomatic sinus osteoma of the face, the mean age was 40 years, sex ratio was 0.38. the frontal sinus was the most affected, 55.5% of cases. Surgical treatment was set for symptomatic patients. The endonasal route was indicated in 6 cases. Recurrence was observed in two patients (11%) having a frontal osteoma and fronto-ethmoid. Outcomes were favorable in the remaining patients, mean follow-up was 36 months.Conclusion: Paranasal sinuses osteoma is a long asymptomatic tumor, but it may be complicated with orbital extending or stroke. Endonasal approach contributed to improve the treatment.Keyswords : Osteoma, paranasal sinus, computed tomography, surgery, endonasal approac
Les MĂ©lanomes Malins Nasosinusiens
Le mélanome malin nasosinusien est une tumeur rare prenant naissance au niveau des mélanocytes de la muqueuse respiratoire. Les auteurs rapportent deux observations de mélanomes malins nasosinusiens suivis et traités au service d\'ORL et de CCF de l\'hÎpital Habib Thameur entre 1999 et 2005. Il s\'agit d\'un homme et d\'une femme ùgés respectivement de 62 et 68 ans. La symptomatologie clinique est dominée par l\'obstruction nasale et l\'épistaxis. Le diagnostic est histologique aprÚs biopsie de la tumeur. Le traitement chirurgical est suivi d\'une radiothérapie externe dans les deux cas.
L\'évolution est marquée par une récidive tumorale dans un cas. Primary mucosal melanoma of the nasal cavity and paranasal sinuses is an uncommun clinical entity occurring on the level of the melanocytes respiratory mucous membrane. The authors report two observations of malignant melanoma of sinonasal mucosa treated between 1999 and 2005. It acts of an old man and a woman respectively 62 and 68 years old, both presented with nasal obstruction and epistaxis. The diagnosis was histological after biopsy of the tumour. The surgical treatment was followed of an external radiotherapy in both cases. The evolution was marked by a local recurrence in one case. Journal Tunisien d\'ORL et de chirurgie cervico-faciale Vol. 16 2006: pp. 50-5
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Improved control of Septoria tritici blotch in durum wheat using cultivar mixtures
Mixtures of cultivars with contrasting levels of disease resistance are capable of suppressing infectious diseases in wheat, as demonstrated in numerous field experiments. Most studies focused on airborne pathogens in bread wheat, while splash-dispersed pathogens have received less attention, and no studies have been conducted in durum wheat. We conducted a two-year field experiment in Tunisia, a major durum wheat producer in the Mediterranean region, to evaluate the performance of cultivar mixtures in controlling the polycyclic, splash-dispersed disease Septoria tritici blotch (STB) in durum wheat. To measure STB severity, we used a novel, high-throughput method based on digital analysis of images captured from 3074 infected leaves collected from 42 and 40 experimental plots on the first and the second year, respectively. This method allowed us to quantify pathogen reproduction on wheat leaves and to acquire a large dataset that exceeds previous studies with respect to accuracy and statistical power. Our analyses show that introducing only 25% of a disease-resistant cultivar into a pure stand of a susceptible cultivar provides a substantial reduction of almost 50% in disease severity. However, adding a second resistant cultivar to the mixture did not further improve disease control, contrary to predictions of epidemiological theory. Susceptible cultivars can be agronomically superior to resistant cultivars or be better accepted by growers for other reasons. Hence, if mixtures with only a moderate proportion of the resistant cultivar provide similar degree of disease control as resistant pure stands, as our analysis indicates, such mixtures are more likely to be accepted by growers
Genome structure and pathogenicity of the fungal wheat pathogen Mycosphaerella graminicola
The phytopathogenic fungus Mycosphaerella graminicola (Fuckel) J. Schröt. in Cohn (asexual stage: Zymoseptoria tritici (Desm.) Quaedvlieg & Crous) causes septoria tritici leaf blotch (STB) in wheat and is one of the most important diseases of this crop worldwide. However, STB control, mainly based on the use of resistant cultivars and fungicides, is significantly hampered by the limited understanding of the genetic and biochemical bases of pathogenicity, and mechanisms of infection and resistance in the host. M. graminicola has a very active sexual cycle under field conditions, which is an important driver of STB epidemics. Moreover, it results in high genetic diversity of field populations that causes a major challenge for the development and sustainable management of resistant cultivars and the discovery of new antifungal compounds. Understanding the role of the sexual and asexual life cycles on genome composition of this versatile pathogen and its infection strategy is crucial in order to develop novel control methods. Chapter 1 is an introduction to the biology and pathogenicity of M. graminicola. In addition, it shortly describes the impact of improved and novel technologies on the speed, scope and scale of comparative genomics research. Chapter 2 provides detailed genetic analyses of two M. graminicola mapping populations, using mainly DArT markers, and the analysis of the meiotic transmission of unequal chromosome numbers. Polymorphisms in chromosome length and number were frequently observed in progeny isolates, of which 15â20% lacked one or more chromosomes despite their presence in one or both parents, but these had no apparent effect on sexual and pathogenic fitness. M. graminicola has up to eight so called dispensable chromosomes that can be easily lost - collectively called the dispensome - which is, so far, the highest number of dispensable chromosomes reported in filamentous fungi. They represent small-sized chromosomes and make up 38% of the chromosome complement of this pathogen. Much of the observed genome plasticity is generated during meiosis and could explain the high adaptability of M. graminicola in the field. The generated linkage map was crucial for finishing the M. graminicola genome sequence. Chapter 3 describes the M. graminicola genome sequence with highlights on genome structure and organization including the eight dispensable chromosomes. The genome comprises a core set of 13 chromosomes and a dispensome, consisting of eight chromosomes that are distinct from the core chromosomes in structure, gene and repeat content. The dispensome contains a higher frequency of transposons and the genes have a different codon use. Most of the genes present one the dispensome are also present on the core chromosomes but little synteny is observed neither between the M. graminicola dispensome and the core chromosomes nor with the chromosomes of other related Dothideomycetes. The dispensome likely originates from ancient horizontal transfer(s) from (an) unknown donor(s). Chapter 4 shows a global analysis of proteins secreted by M. graminicola in apoplastic fluids during infection. It focuses mainly on fungal proteins secreted in a compatible interaction. The study showed that many of the annotated secreted proteins have putative functions in fungal pathogenicity, such as cell wall degrading enzymes and proteases, but the function of a substantial number of the identified proteins is unknown. During compatible interactions proteins are primarily secreted during the later stages. However, many pathogenesis-related host proteins, such as PR-2, PR-3 and PR-9, accumulated earlier and at higher concentrations during incompatible interactions, indicating that fungal effectors are recognized by resistant plants and trigger resistant gene-mediated defence responses, though without a visible hypersensitive response. Chapter 5 further details the initial identification and characterization of necrosis-inducing proteins that are produced in culture filtrates (CFs) of M. graminicola. The necrosis-inducing activity of CFs is light dependent and inactivated by proteinase K and heat treatment (100C). This is reminiscent of the necrosis-inducing properties of host selective toxins of other Dothideomycete pathogens such as Stagonospora nodorum and Pyrenophora tritici-repentis. Subsequent purifications of CFs and mass spectrometry identified several candidate proteins with necrosis-inducing activity. Heterologous expression of the two most prominent proteins in Pichia pastoris produced sufficient quantities for infiltration assays in a panel of wheat cultivars that showed differential responses, suggesting specific recognition. Chapter 6 provides a general discussion of the thesis and puts the results obtained in a broader perspective with a focus on the genome structure of M. graminicola and its function. In addition, aspects of the hemi-biotrophic lifestyle, the relevance of secreted proteins for the wheat-M. graminicola pathosystem in relation to gene-for-gene models and the potential implications for resistance breeding strategies are discussed
Gouvernance régionale et développement rural intégré en Italie. Enseignements pour les régions françaises
Convention dâassistance technique (Ă©valuation in itinere du PDRH) entre le CIHEAM-IAMM et le MinistĂšre de lâAlimentation, de l'Agriculture et de la PĂȘche de la RuralitĂ© et de lâAmĂ©nagement du Territoire (MAAPRAT), Direction gĂ©nĂ©rale des politiques agricole, agroalimentaire et des territoires (DGPAAT), sous-direction du dĂ©veloppement rural et du cheval.International audienceCette Ă©tude a pour objectif dâanalyser les modalitĂ©s de mises en Ćuvre et dâintĂ©gration des politiques europĂ©ennes au niveau des RĂ©gions italiennes. De part leurs histoire et leur mode de fonctionnement institutionnel, les RĂ©gions italiennes reprĂ©sentent un modĂšle de dĂ©centralisation avancĂ©e susceptible dâapporter des Ă©lĂ©ments de rĂ©ponses aux rĂ©flexions actuelles sur le devenir de la PAC post 2013 et son Ă©ventuelle intĂ©gration au sein de la politique rĂ©gionale de lâUE
Gouvernance régionale et développement rural intégré en Italie. Enseignements pour les régions françaises
Convention dâassistance technique (Ă©valuation in itinere du PDRH) entre le CIHEAM-IAMM et le MinistĂšre de lâAlimentation, de l'Agriculture et de la PĂȘche de la RuralitĂ© et de lâAmĂ©nagement du Territoire (MAAPRAT), Direction gĂ©nĂ©rale des politiques agricole, agroalimentaire et des territoires (DGPAAT), sous-direction du dĂ©veloppement rural et du cheval.International audienceCette Ă©tude a pour objectif dâanalyser les modalitĂ©s de mises en Ćuvre et dâintĂ©gration des politiques europĂ©ennes au niveau des RĂ©gions italiennes. De part leurs histoire et leur mode de fonctionnement institutionnel, les RĂ©gions italiennes reprĂ©sentent un modĂšle de dĂ©centralisation avancĂ©e susceptible dâapporter des Ă©lĂ©ments de rĂ©ponses aux rĂ©flexions actuelles sur le devenir de la PAC post 2013 et son Ă©ventuelle intĂ©gration au sein de la politique rĂ©gionale de lâUE