Synergistic Degradation of Linuron by a Bacterial Consortium and Isolation of a Single Linuron-Degrading Variovorax Strain

The bacterial community composition of a linuron-degrading enrichment culture and the role of the individual strains in linuron degradation have been determined by a combination of methods, such as denaturing gradient gel electrophoresis of the total 16S rRNA gene pool, isolation and identification of strains, and biodegradation assays. Three strains, Variovorax sp. strain WDL1, Delftia acidovorans WDL34, and Pseudomonas sp. strain WDL5, were isolated directly from the linuron-degrading culture. In addition, subculture of this enrichment culture on potential intermediates in the degradation pathway of linuron (i.e., N,O-dimethylhydroxylamine and 3-chloroaniline) resulted in the isolation of, respectively, Hyphomicrobium sulfonivorans WDL6 and Comamonas testosteroni WDL7. Of these five strains, only Variovorax sp. strain WDL1 was able to use linuron as the sole source of C, N, and energy. WDL1 first converted linuron to 3,4-dichloroaniline (3,4-DCA), which transiently accumulated in the medium but was subsequently degraded. To the best of our knowledge, this is the first report of a strain that degrades linuron further than the aromatic intermediates. Interestingly, the rate of linuron degradation by strain WDL1 was lower than that for the consortium, but was clearly increased when WDL1 was coinoculated with each of the other four strains. D. acidovorans WDL34 and C. testosteroni WDL7 were found to be responsible for degradation of the intermediate 3,4-DCA, and H. sulfonivorans WDL6 was the only strain able to degrade N,O-dimethylhydroxylamine. The role of Pseudomonas sp. strain WDL5 needs to be further elucidated. The degradation of linuron can thus be performed by a single isolate, Variovorax sp. strain WDL1, but is stimulated by a synergistic interaction with the other strains isolated from the same linuron-degrading culture

Identificación de secuencias que se expresan diferencialmente en la interacción no compatible Musa acuminata - Mycosphaerella fijiensis Morelet

Black leaf streak disease caused by Mycosphaerella fijiensis Morelet is considered the most destructive and costly foliar disease of bananas and plantain. An important step for the elucidation of molecular mechanisms of the disease resistance is to know about genes involved in plant defense response to pathogens. Identification of differentially expressed sequences in resistant genotype ‘Calcutta 4’ (Musa acuminata, AA) at an early stage of infection with M. fijiensis (6 to 12 days post inoculation) from a suppressed subtractive library (SSH) was carried out. A number of 63 ESTs, which include 42 singletons and 21 contigs were obtained by assembling 97 sequences with CAP3 algorithm. Identification of sequences according to their homology with sequences stated at protein non-redundant database GenBank, allowed to gather them in six functional categories: protein destiny (1.6%), oxidative stress (4.8%), metabolism (6.3%), energy production (6.3%), unknown function (38.1%) and without homology (42.8%). Results obtained will contribute to a better understanding of pathosystem, which allow the design of new strategies related to genetic improvement of banana.Keywords: Black leaf streak disease, expressed sequence tags, functional gene classification, Musa spp.,subtractive libraryLa Sigatoka negra se considera la enfermedad foliar más destructiva y costosa a nivel mundial que afecta la producción de bananos y plátanos. El conocimiento acerca de los genes involucrados en la respuesta de defensa en la planta ante el ataque por patógenos, constituye un paso importante para la elucidación de los mecanismos moleculares de resistencia a enfermedades. En este estudio a partir de una biblioteca sustractiva de ácido desoxirribonucleico complementaria (ADNc) realizada en el genotipo resistente ‘Calcutta 4’ (Musa acuminata, AA) en un estadio temprano de la infección con M. fijiensis (6 a 12 días posteriores a la inoculación), se realizó la identificación de las secuencias expresadas diferencialmente. Como resultado del ensamblaje con la herramienta bioinformática CAP3, de 97 secuencias de la biblioteca sustractiva fueron obtenidas 63 secuencias blanco expresadas, que incluían 42 secuencias aisladas y 21 ensamblajes. La identificación de las mismas según su homología con secuencias anotadas en la base de datos para proteínas no redundante (GenBank), permitió agruparlas en: destino de proteínas (1.6%), estrés oxidativo (4.8%), metabolismo (6.3%), producción de energía (6.3%), función desconocida (38.1%) y sin homología (42.8%). Los resultados obtenidos contribuirán a un mejor entendimiento del patosistema, lo cual permitirá el diseño de nuevas estrategias relacionadas con el mejoramiento genético en banano.Palabras clave: biblioteca sustractiva, clasificación funcional de genes, Musa spp., secuencias blanco expresadas, Sigatoka negr

Identification of virulence associated loci in the emerging broad host range plant pathogen Pseudomonas fuscovaginae

BACKGROUND: Pseudomonas fuscovaginae (Pfv) is an emerging plant pathogen of rice and also of other gramineae plants. It causes sheath brown rot disease in rice with symptoms that are characterized by brown lesions on the flag leaf sheath, grain discoloration and sterility. It was first isolated as a high altitude pathogen in Japan and has since been reported in several countries throughout the world. Pfv is a broad host range pathogen and very little is known about its virulence mechanisms. RESULTS: An in planta screen of 1000 random independent Tn5 genomic mutants resulted in the isolation of nine mutants which showed altered virulence. Some of these isolates are mutated for functions which are known to be virulence associated factors in other phytopathogenic bacteria (eg. pil gene, phytotoxins and T6SS) and others might represent novel virulence loci. CONCLUSIONS: Being an emerging pathogen worldwide, the broad host range pathogen Pfv has not yet been studied for its virulence functions. The roles of the nine loci identified in the in planta screen are discussed in relation to pathogenicity of Pfv. In summary, this article reports a first study on the virulence of this pathogen involving in planta screening studies and suggests the presence of several virulence features with known and novel functions in the Pseudomonas group of bacteria

Global distribution of <I>Erysiphe platani</I>: new records, teleomorph formation and re-examination of herbarium collections

Une enquête globale aété menée sur la propagation d\u27Erysiphe platani agent causal de l\u27oïdium du platane. Le téléomorphe d\u27E. platani a été découvert dans les pays où l\u27anamorphe existe déjà depuis plusieurs années. Les premières observations des chasmothèces de ce champignon ont été réalisées en Autriche, en République tchèque, en France, en Italie et en Slovaquie. Par ailleurs, la présence de l\u27holomorphe d\u27E. platani a été signalée en Belgique, en Croatie et au Danemark. La présence de ce champignon en Suède et dans deux pays d\u27Afrique du Nord (Algérie et Maroc) a été confirmée. Cette étude donne la description des caractéristiques morphologiques, ainsi que les illustrations et la distribution mondiale d\u27E. platani. En outre, les collections d\u27herbiers de l\u27oïdium de Platanus spp. ont été réexaminées et révisées. La présence de Phyllactinia guttata sur le platane est discutée.A global survey of the spread of the Platanus powdery mildew, Erysiphe platani, has been carried out. E. platani teleomorph formation was recorded in countries where the fungus anamorph has been present for several years. The first findings of chasmothecia were recorded in Austria, Czech Republic, France, Italy and Slovakia. New records of E. platani (including the teleomorph) were found in Belgium, Croatia and Denmark. The occurrence of this fungus in Sweden and in two countries of North Africa (Algeria and Morocco) was confirmed. Descriptions of morphological features, illustrations, and worldwide distribution of E. platani are provided. Herbarium collections of powdery mildews on Platanus spp. were re-examined and revised. The occurrence of Phyllactinia guttata on Platanus is discussed and questioned.</p

Lipopeptide families at the interface between pathogenic and beneficialPseudomonas-plant interactions

Lipopeptides (LPs) are a prominent class of molecules among the steadily growing spectrum of specialized metabolites retrieved from Pseudomonas, in particular soil-dwelling and plant-associated isolates. Among the multiple LP families, pioneering research focussed on phytotoxic and antimicrobial cyclic lipopeptides (CLPs) of the ubiquitous plant pathogen Pseudomonas syringae (syringomycin and syringopeptin). Their non-ribosomal peptide synthetases (NRPSs) are embedded in biosynthetic gene clusters (BGCs) that are tightly co-clustered on a pathogenicity island. Other members of the P. syringae group (Pseudomonas cichorii) and some species of the Pseudomonas asplenii group and Pseudomonas fluorescens complex have adopted these biosynthetic strategies to co-produce their own mycin and peptin variants, in some strains supplemented with an analogue of the P. syringae linear LP (LLP), syringafactin. This capacity is not confined to phytopathogens but also occurs in some biocontrol strains, which indicates that these LP families not solely function as general virulence factors. We address this issue by scrutinizing the structural diversity and bioactivities of LPs from the mycin, peptin, and factin families in a phylogenetic and evolutionary perspective. BGC functional organization (including associated regulatory and transport genes) and NRPS modular architectures in known and candidate LP producers were assessed by genome mining.status: publishe

Fluridone suppresses pathogen-induced transcription of ABA biosynthesis and response genes.

<p>(A) through (C). Relative expression of ABA biosynthesis and responsive genes, <i>OsNCED3</i>, <i>OsLip9</i> and <i>OsRab16</i>, in control (Ctrl) and fluridone-pretreated (0.4 µM) IRBB3 leaves inoculated with PXO99. Transcript levels were normalized using eukaryotic elongation factor <i>eEF1α</i> as an internal reference and expressed relative to the normalized expression levels in mock-inoculated control plants at the appropriate time point. Data are means ± SD of two technical and two biological replicates from a representative experiment, each biological replicate representing a pooled sample from 3 individual plants. Two sets of independent experiments were carried out with similar results. Asterisks indicate statistically significant differences per treatment compared to either control (0 dpi) or mock-treated samples (1, 2, 4 and 8 dpi).</p

ABA counteracts SA-mediated defenses to <i>Xoo</i>.

<p>(A) through (C). Expression of SA marker genes <i>OsWRKY45, OsNPR1</i> and <i>OsWRKY13</i> in control (Ctrl) and ABA pretreated IRBB3 leaves inoculated with PXO99. Transcript levels were normalized using eukaryotic elongation factor eEF1α as an internal reference and for each treatment expressed relative to the normalized expression levels in mock-inoculated control plants at the appropriate time point. Data are means ± SD of two technical and two biological replicates from a representative experiment, each biological replicate representing a pooled sample from 3 individual plants. Asterisks indicate statistically significant differences per treatment compared to either control (0 dpi) or mock-treated samples (1, 2, 4 and 8 dpi). (D). Effect of single and combined pretreatment with ABA (100 µM) and/or SA (500 µM) on BLB development in susceptible IRBB3 plants. Lesions were measured 14 days after inoculation with PXO99. Data are means ± SE of at least 10 plants. Different letters indicate statistically significant differences (Mann-Whitney; n ≥20; α = 0.05) (E) and (F). Effect of exogenous ABA treatment (100 µM) on BLB development in <i>OsNPR1</i>-OX and <i>OsWRKY13</i>-OX lines and their respective WT Taipei and Mudanjiang. Data are means ± SE of at least 10 plants. Different letters indicate statistically significant differences (Mann-Whitney; n ≥20; α = 0.05). Repetition of experiments led to results similar to those shown.</p

Dynamics of ABA pathway in response to virulent <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> (<i>Xoo</i>) infection.

<p>(A) through (D). Effect of ABA pretreatment on ABA-biosynthesis (<i>OsNCED3</i>, <i>OsNCED4</i>) and ABA-responsive genes (<i>OsLip9</i> and <i>OsRab16</i>) in IRBB3 leaves inoculated with <i>Xoo</i> strain PXO99. For details on ABA pretreatment and <i>Xoo</i> inoculation, see legend to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067413#pone-0067413-g001" target="_blank">Figure 1</a>. Transcript levels were normalized using eukaryotic elongation factor <i>eEF1α</i> as an internal reference and, for each treatment, expressed relative to the normalized expression levels in mock-inoculated control plants at the appropriate time point. Data are means ± SD of two technical and two biological replicates from a representative experiment, each biological replicate representing a pooled sample from 3 individual plants. Two sets of independent experiments were carried out with similar results. Asterisks indicate statistically significant differences per treatment compared to either control (0 dpi) or mock-treated samples (1, 2, 4 and 8 dpi).</p