Dinâmica populacional de Pseudomonas savastanoi pv. phaseolicola em feijoeiro, durante as fases epifítica e patogênica

The objective of this work was to monitor traits of the life cycle of Pseudomonas savastanoi pv. phaseolicola, in order to better understand the outbreak of bean halo blight, originating from a bacterial population in asymptomatic plants. Five experiments were conducted in the field, in greenhouses, and in humidity chambers. Changes in population size were evaluated in three field plantings, by introducing the bacteria in contamination focal points and observing the weather conditions favoring an outbreak. The dispersion of the bacteria in the field was followed by isolation and Bio‑PCR analysis. Two assays were conducted in greenhouses and humidity chambers to evaluate the effect of leaf age on disease expression and the relationship between population level and number of leaf spots. The bacteria multiply intensively when in contact with a compatible host and reach high population sizes, with or without symptoms. The most favorable factor for bacterial multiplication and symptom triggering was water, and its role in the changeover from the epiphytic to the pathogenic phase might be linked to rainfall volume and intensity. Bacterial asymptomatic dispersion in the field is greater than disease emergence. In Brazil, the bacteria should be categorized as a present quarantine pest.O objetivo deste trabalho foi monitorar características do ciclo de vida de Pseudomonas savastanoi pv. phaseolicola, para melhor compreender a manifestação do crestamento aureolado do feijoeiro, originada de uma população bacteriana em plantas assintomáticas. Cinco experimentos foram conduzidos em campo, casas de vegetação e câmaras de cultura. Alterações no tamanho da população foram avaliadas em três plantios no campo, por meio da introdução da bactéria em focos de contaminação e da observação das condições climáticas que favoreceram a manifestação da doença. A dispersão da bactéria no campo foi acompanhada por isolamento e análise Bio‑PCR. Dois ensaios foram conduzidos em casas de vegetação e câmaras de cultura, para avaliar o efeito da idade das folhas na expressão da doença e a relação entre o nível populacional e o número de manchas foliares. A bactéria multiplica-se intensamente logo que entra em contato com hospedeiro compatível e atinge níveis populacionais elevados, com a presença ou não de sintomas. O fator que mais favoreceu a multiplicação bacteriana e o surgimento dos sintomas foi a água, e seu papel na passagem da fase epifítica à patogênica pode estar associado ao volume e à intensidade das chuvas. A dispersão não sintomática da bactéria no campo é maior que o aparecimento da doença. No Brasil, a bactéria deve ser categorizada como praga quarentenária presente

A Functional and Regulatory Network Associated with PIP Expression in Human Breast Cancer

BACKGROUND: The PIP (prolactin-inducible protein) gene has been shown to be expressed in breast cancers, with contradictory results concerning its implication. As both the physiological role and the molecular pathways in which PIP is involved are poorly understood, we conducted combined gene expression profiling and network analysis studies on selected breast cancer cell lines presenting distinct PIP expression levels and hormonal receptor status, to explore the functional and regulatory network of PIP co-modulated genes. PRINCIPAL FINDINGS: Microarray analysis allowed identification of genes co-modulated with PIP independently of modulations resulting from hormonal treatment or cell line heterogeneity. Relevant clusters of genes that can discriminate between [PIP+] and [PIP-] cells were identified. Functional and regulatory network analyses based on a knowledge database revealed a master network of PIP co-modulated genes, including many interconnecting oncogenes and tumor suppressor genes, half of which were detected as differentially expressed through high-precision measurements. The network identified appears associated with an inhibition of proliferation coupled with an increase of apoptosis and an enhancement of cell adhesion in breast cancer cell lines, and contains many genes with a STAT5 regulatory motif in their promoters. CONCLUSIONS: Our global exploratory approach identified biological pathways modulated along with PIP expression, providing further support for its good prognostic value of disease-free survival in breast cancer. Moreover, our data pointed to the importance of a regulatory subnetwork associated with PIP expression in which STAT5 appears as a potential transcriptional regulator

Deciphering cellular states of innate tumor drug responses

BACKGROUND: The molecular mechanisms underlying innate tumor drug resistance, a major obstacle to successful cancer therapy, remain poorly understood. In colorectal cancer (CRC), molecular studies have focused on drug-selected tumor cell lines or individual candidate genes using samples derived from patients already treated with drugs, so that very little data are available prior to drug treatment. RESULTS: Transcriptional profiles of clinical samples collected from CRC patients prior to their exposure to a combined chemotherapy of folinic acid, 5-fluorouracil and irinotecan were established using microarrays. Vigilant experimental design, power simulations and robust statistics were used to restrain the rates of false negative and false positive hybridizations, allowing successful discrimination between drug resistance and sensitivity states with restricted sampling. A list of 679 genes was established that intrinsically differentiates, for the first time prior to drug exposure, subsequently diagnosed chemo-sensitive and resistant patients. Independent biological validation performed through quantitative PCR confirmed the expression pattern on two additional patients. Careful annotation of interconnected functional networks provided a unique representation of the cellular states underlying drug responses. CONCLUSION: Molecular interaction networks are described that provide a solid foundation on which to anchor working hypotheses about mechanisms underlying in vivo innate tumor drug responses. These broad-spectrum cellular signatures represent a starting point from which by-pass chemotherapy schemes, targeting simultaneously several of the molecular mechanisms involved, may be developed for critical therapeutic intervention in CRC patients. The demonstrated power of this research strategy makes it generally applicable to other physiological and pathological situations

Population dynamics of Pseudomonas savastanoi pv. phaseolicola in bean, throughout the epiphytic and pathogenic phases

The objective of this work was to monitor traits of the life cycle of Pseudomonas savastanoi pv. phaseolicola, in order to better understand the outbreak of bean halo blight, originating from a bacterial population in asymptomatic plants. Five experiments were conducted in the field, in greenhouses, and in humidity chambers. Changes in population size were evaluated in three field plantings, by introducing the bacteria in contamination focal points and observing the weather conditions favoring an outbreak. The dispersion of the bacteria in the field was followed by isolation and Bio-PCR analysis. Two assays were conducted in greenhouses and humidity chambers to evaluate the effect of leaf age on disease expression and the relationship between population level and number of leaf spots. The bacteria multiply intensively when in contact with a compatible host and reach high population sizes, with or without symptoms. The most favorable factor for bacterial multiplication and symptom triggering was water, and its role in the changeover from the epiphytic to the pathogenic phase might be linked to rainfall volume and intensity. Bacterial asymptomatic dispersion in the field is greater than disease emergence. In Brazil, the bacteria should be categorized as a present quarantine pest

Influence du nématode des tiges, Ditylenchus dipsaci (Kühn) Fil. dans le développement de la bactériose « café au lait » de l'ail (Allium sativum L.) occasionnée par un biovar de Pseudomonas fluorescens Migula

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Recherches sur la résistance des sols aux maladies. XV. Comparaison des populations de Pseudomonas fluorescents dans un sol résistant et un sol sensible aux fusarioses vasculaires

Dans un article précédent, nous avons montré que la compétition pour le fer joue un rôle dans le mécanisme de résistance des sols de Chateaurenard. L’objet de cet article est donc d’apprécier la participation des Pseudomonas fluorescents à cette compétition. Les populations de Pseudomonas fluorescents du sol résistant de Chateaurenard et du sol sensible de Carquefou sont comparées pour leur densité dans la terre adhérente (rhizoplan) ou non aux racines et pour leur aptitude à se développer en milieu carencé en fer. Les sols sont cultivés et maintenus à 3 valeurs différentes de potentiel hydrique : pF 1, pF 2,5 et pF 4. Au sein de la microflore aérobie totale, la fréquence de Pseudomonas fluorescents est 7 à 8 fois plus faible dans le sol résistant que dans le sol sensible. L’effectif des populations bactériennes, plus élevé dans le rhizoplan que dans la terre, varie peu avec les valeurs de potentiel hydrique auxquelles sont maintenus les sols. Les souches de Pseudomonas fluorescents collectées lors des dénombrements bactériens sont cultivées en milieu succinate additionné de concentrations croissantes de 8-hydroxyquinoléine. Chaque souche est caractérisée par la concentration minimale inhibitrice (CMI) de ce ligand qui diminue la disponibilité en fer du milieu. Les populations du rhizoplan et des sols à pF 1 et pF 2,5 sont respectivement mieux adaptées à la carence en fer que celles de la terre sans racine et des sols à pF 4. Les populations de Pseudomonas du sol résistant sont par ailleurs significativement plus sensibles à la carence en fer que celles du sol sensible. La participation des Pseudomonas fluorescents à la compétition pour le fer et donc au mécanisme de résistance des sols de Chateaurenard semble réduite. Ils sont en effet moins nombreux en valeur relative et moins aptes à croître en milieu carencé en fer que ceux du sol sensible de Carquefou.In a previous paper, we showed that competition for iron plays a role in the mechanism of wilt suppressiveness of the soils from Chateaurenard. The aim of the present work was to test the role of fluorescent Pseudomonas in this competition. The bulk soil and rhizoplane populations of fluorescent Pseudomonas from a Chateaurenard suppressive soil and from a Carquefou conducive soil were compared in this respect and also for their ability to grow in a low iron-content medium. In addition, they were maintained at three different levels of hydric potential : pF 1, pF 2.5 and pF 4. The percentage of fluorescent Pseudomonas in the total aerobic microflora was 7 or 8 times lower in the suppressive soil than in the conducive soil. The size of the bacterial population, higher in the rhizoplane than in the bulk soil, depended on the soil matric potential. The strains of fluorescent Pseudomonas collected during bacterial counting were grown on a succinate medium containing increasing concentrations of 8-hydroxyquinoline. Each strain was characterized by its inhibitory minimal concentration (IMC) of this ligand, which decreases iron availability in the medium. The populations from the rhizoplane and from the soils maintained at pF 1 and pF 2.5 were better adapted to iron deficiency than those from the bulk soil and from the soils maintained at pF 4. The populations of fluorescent Pseudomonas from the suppressive soil were significantly more sensitive to iron deficiency than those from the conducive soil. The participation of fluorescent Pseudomonas in competition for iron and also in the suppressiveness of the Chateaurenard soils seems limited, in so for as their relative level and ability to grow in an iron-deficient medium was lower than those from the conducive soil of Carquefou

Description and identification of the new phytopathogenic bacterium causing bacterial black spots on Corn salad (Valerianella locusta), as Acidovorax valerianellae

Description and identification of the new phytopathogenic bacterium causing bacterial black spots on Corn salad ([i]Valerianella locusta[/i]), as[i] Acidovorax valerianellae[/i]. 10. International Conference of Plant Pathogenic Bacteri