Contribution of Phenotypic Heterogeneity to plant colonization by Pseudomonas syringae

In bacterial clonal populations, cell to cell differences can be originated by the response to different stimuli present in the environment. However, the sources of variation may not always be directly correlated with stimuli. In some cases, these differences are merely a consequence of the noise in gene expression or in others, a programmed event under genetic or epigenetic control. The presence of different phenotypes can allow some individuals to survive sudden environmental changes (risk-spreading) and can also lead to the division of labour between individuals. The relevance of this process has been demonstrated in Salmonella and other human pathogens for the expression of virulence genes and has been linked to the establishment of a successful infection. However, little is known about the importance of this process in the colonization of the plant tissue. In the phytopathogenic bacteria Pseudomonas syringae we have demonstrated that the T3SS show phenotypic heterogeneity during the colonization of the plant. We have also established that flagella is expressed and displays phenotypic heterogeneity during colonization of the apoplast. These processes are counter-regulated. Nonetheless, all possible combinations for T3SS and flagella expression are formed within the apoplastic population, including T3SSON/FlagellaON and T3SSOFF/FlagellaOFF bacteria. We show that expression and function of these virulence-relevant loci impact bacterial fitness and describe how plant defences modulate their expression at the population level. All these observations support the notion that the phenotypic heterogeneity is a relevant process for the adaptation of P. syringae to the plant host.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Heterogeneidad fenotípica en el Sistema de Secreción tipo III de Pseudomonas syringae durante la interacción con la planta

La heterogeneidad fenotípica es un fenómeno que se ha descrito en poblaciones bacterianas de diversas especies. Un patrón de expresión génica heterogéneo puede llegar a volverse bimodal en ambientes homogéneos, proceso conocido como bistabilidad. El desarrollo de métodos de análisis de células individuales, como la microscopía confocal, la citometría o la microfluídica, ha llevado a la identificación de nuevos ejemplos de variación fenotípica y de biestabilidad. La relevancia de estos procesos se ha demostrado en patógenos humanos y de animales. No obstante, se conoce muy poco sobre la relevancia de este tipo de procesos en el proceso de adaptación a huéspedes no animales. P. syringae es una bacteria patógena de plantas con un amplio rango de hospedador, existiendo más de 50 patovares. La virulencia de Pseudomonas syringae dependiende del Sistema de Secreción Tipo III (T3SS) y de los efectores tipo III (T3E). Mediante fusiones transcripcionales a proteínas fluorescentes generadas en el genoma de P. syringae pv. phaseolicola, y el uso de microscopía de fluorescencia y citometría de flujo, nuestro laboratorio ha demostrado que la expresión del T3SS y de T3E es heterogénea en el interior de la planta y biestable en medio mínimo. En este trabajo presentamos los resultados obtenidos en nuestro análisis del impacto de la expresión heterogénea del T3SS para la adaptación a la planta, que incluyen la evaluación de la viabilidad de las variantes (T3SSON/T3SSOFF) en el apoplasto de la hoja, y de la dinámica de expresión en la población en diferentes escenarios de activación de defensa en la planta.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A combined procedure to evaluate the global antioxidant response of bread

International audienc

Dynamics of heterogeneous populations of Pseudomonas syringae within plant tissues reveal a diversity of interactions with potential evolutionary

Bacterial populations have been traditionally assumed to be clonal, and as such, genetically and phenotipically identical. However, research carried out in the last few decades has proven this view naïve. Formation of distinct bacterial subpopulations has been seen to take place under stressing conditions, such as those encountered by pathogenic bacteria within the host, and is often associated to epigenetic changes that give rise to phenotypic heterogeneity without altering the genotype (Casadesús and Low, 2013). A somewhat different example of reversible genomic changes that can affect virulence can be found in Pseudomonas syringae pv. phaseolicola, the causing agent of halo blight in bean. Inoculation of this bacterium into resistant plants triggers the excision of PPHGI-1, a genomic island encoding the effector that causes the resistance, AvrPphB, from the chromosome (Pitman et al, 2005). In recent years, extensive research has focused on the interaction between individual bacterial strains and the plant host (Dodds & Rathjen, 2010), although little is known about how heterogeneous (or mixed isogenic) bacterial populations of a given pathogen interact and develop with the host plant. In this work, we aimed to analyse how mixed isogenic populations, varying in their virulence, develop within the plant host. Using confocal microscopy, we investigate the cellular basis that determine whether co-existing P. syringae bacteria with different virulence capabilities interfere with the growth of each other. Moreover, we analyse the consequences of such interferences on the development of disease and the activation of a defence response.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

A novel targeted RNA-Seq panel identifies a subset of adult patients with acute lymphoblastic leukemia with BCR-ABL1-like characteristics

BCR-ABL1-like B-cell precursor acute lymphoblastic leukemia (BCP-ALL) remains poorly characterized in adults. We sought to establish the frequency and outcome of adolescent and adult BCR-ABL1-like ALL using a novel RNA-Seq signature in a series of patients with BCP-ALL. To this end, we developed and tested an RNA-Seq custom panel of 42 genes related to a BCR-ABL1-like signature in a cohort of 100 patients with BCP-ALL and treated with risk-adapted ALL trials. Mutations related to BCR-ABL1-like ALL were studied in a panel of 33 genes by next-generation sequencing (NGS). Also, CRLF2 overexpression and IKZF1/CDKN2A/B deletions were analyzed. Twenty out of 79 patients (12-84 years) were classified as BCR-ABL1-like (25%) based on heatmap clustering, with significant overexpression of ENAM, IGJ, and CRLF2 (P ≤ 0.001). The BCR-ABL1-like subgroup accounted for 29% of 15-60-year-old patients, with the following molecular characteristics: CRLF2 overexpression (75% of cases), IKZF1 deletions (64%), CDKN2A/B deletions (57%), and JAK2 mutations (57%). Among patients with postinduction negative minimal residual disease, those with the BCR-ABL1-like ALL signature had a higher rate of relapse and lower complete response duration than non-BCR-ABL1-like patients (P = 0.007). Thus, we have identified a new molecular signature of BCR-ABL1-like ALL that correlates with adverse prognosis in adult patients with ALL