Determinantes moleculares que participan en la interacción Fusarium oxysporum-tomate

En este trabajo se ha investigado sobre las bases moleculares que determinan la patogenicidad del hongo Fusarium oxysporum f. sp. lycopersici sobre plantas de tomate, estudiando particularmente la importancia de la detoxificación de compuestos antifúngicos producidos por las plantas de tomate, así como la relación entre la morfogénesis del patógeno y el desarrollo de la enfermedad. Las enzimas detoxificadoras de saponinas, producidas por hongos patógenos, están implicadas en el proceso de infección de sus plantas hospedadoras. F. oxysporum produce la enzima tomatinasa Tom1, que degrada la α-tomatina hasta derivados menos tóxicos. Para estudiar el papel del gen tom1 en la virulencia de F. oxysporum, se ha llevado a cabo la interrupción dirigida y la expresión constitutiva del gen en la estirpe silvestre del hongo. El proceso de infección de plantas de tomate inoculadas con transformantes del hongo con expresión constitutiva de la enzima Tom1 resulta en un incremento en el desarrollo de los síntomas de enfermedad. Por el contrario, las plantas de tomate infectadas con los mutantes deficientes en el gen muestran un retraso en el proceso de infección, lo que indica que Tom1, aunque no es esencial para la patogenicidad, es necesaria para la virulencia completa de F. oxysporum. La actividad tomatinasa total en las estirpes deficientes (Δtom1) se ve reducida solo un 25%, y se observa β2- tomatina como el mayor producto de hidrólisis de la saponina in vitro. El análisis in silico del genoma de F. oxysporum revela la existencia de cuatro posibles genes responsables de otras tantas tomatinasas con identidad a otras ortólogas de la familia 3 de glicosil hidrolasas. Los productos de estos genes podrían ser los responsables de la actividad tomatinasa reminiscente en los mutantes Δtom1, y por tanto, la detoxificación de la α-tomatina en F. oxysporum sería llevada a cabo por varias actividades enzimáticas independientes, lo que sugiere la importancia de estas enzimas durante el proceso de infección. En otro capítulo, se ha estudiado si la causa de la avirulencia del mutante ΔchsV de F. oxysporum, deficiente en un gen sintasa de quitina de..

The Fusarium oxysporum gnt2, Encoding a Putative NAcetylglucosamine Transferase, Is Involved in Cell Wall Architecture and Virulence

With the aim to decipher the molecular dialogue and cross talk between Fusarium oxysporum f.sp. lycopersci and its host during infection and to understand the molecular bases that govern fungal pathogenicity, we analysed genes presumably encoding N-acetylglucosaminyl transferases, involved in glycosylation of glycoproteins, glycolipids, proteoglycans or small molecule acceptors in other microorganisms. In silico analysis revealed the existence of seven putative N-glycosyl transferase encoding genes (named gnt) in F. oxysporum f.sp. lycopersici genome. gnt2 deletion mutants showed a dramatic reduction in virulence on both plant and animal hosts. Δgnt2 mutants had αalterations in cell wall properties related to terminal αor β-linked N-acetyl glucosamine. Mutant conidia and germlings also showed differences in structure and physicochemical surface properties. Conidial and hyphal aggregation differed between the mutant and wild type strains, in a pH independent manner. Transmission electron micrographs of germlings showed strong cell-to-cell adherence and the presence of an extracellular chemical matrix. Δgnt2 cell walls presented a significant reduction in N-linked oligosaccharides, suggesting the involvement of Gnt2 in N-glycosylation of cell wall proteins. Gnt2 was localized in Golgi-like sub-cellular compartments as determined by fluorescence microscopy of GFP::Gnt2 fusion protein after treatment with the antibiotic brefeldin A or by staining with fluorescent sphingolipid BODIPY-TR ceramide. Furthermore, density gradient ultracentrifugation allowed colocalization of GFP::Gnt2 fusion protein and Vps10p in subcellular fractions enriched in Golgi specific enzymatic activities. Our results suggest that N-acetylglucosaminyl transferases are key components for cell wall structure and influence interactions of F. oxysporum with both plant and animal hosts during pathogenicity

Análisis molecular de la patogénesis en Fusarium oxysporum

El proceso de infección del hongo Fusarium oxysporum es complejo y requiere algunos mecanismos bien regulados: 1) el reconocimiento de señales de la planta, 2) la adhesión a la superficie de la raíz y la diferenciación de hifas de penetración, 3) la invasión del córtex de la raíz y la degradación de barreras físicas hasta llegar al tejido vascular, 4) adaptación al entorno adverso del tejido vegetal, incluyendo la tolerancia a compuestos antifúngicos, 5) la proliferación de las hifas y producción de conidios en los vasos del xilema y, 6) la secreción de factores de virulencia tales como enzimas, péptidos o fitotoxina

Distinct colonization patterns and cDNA-AFLP transcriptome profiles in compatible and incompatible interactions between melon and different races of Fusarium oxysporum f. sp. melonis

Background: Fusarium oxysporum f. sp. melonis Snyd. & Hans. (FOM) causes Fusarium wilt, the most important infectious disease of melon (Cucumis melo L.). The four known races of this pathogen can be distinguished only by infection on appropriate cultivars. No molecular tools are available that can discriminate among the races, and the molecular basis of compatibility and disease progression are poorly understood. Resistance to races 1 and 2 is controlled by a single dominant gene, whereas only partial polygenic resistance to race 1,2 has been described. We carried out a large-scale cDNA-AFLP analysis to identify host genes potentially related to resistance and susceptibility as well as fungal genes associated with the infection process. At the same time, a systematic reisolation procedure on infected stems allowed us to monitor fungal colonization in compatible and incompatible host-pathogen combinations. Results: Melon plants (cv. Charentais Fom-2), which are susceptible to race 1,2 and resistant to race 1, were artificially infected with a race 1 strain of FOM or one of two race 1,2 w strains. Host colonization of stems was assessed at 1, 2, 4, 8, 14, 16, 18 and 21 days post inoculation (dpi), and the fungus was reisolated from infected plants. Markedly different colonization patterns were observed in compatible and incompatible host-pathogen combinations. Five time points from the symptomless early stage (2 dpi) to obvious wilting symptoms (21 dpi) were considered for cDNA-AFLP analysis. After successful sequencing of 627 transcript-derived fragments (TDFs) differentially expressed in infected plants, homology searching retrieved 305 melon transcripts, 195 FOM transcripts expressed in planta and 127 orphan TDFs. RNA samples from FOM colonies of the three strains grown in vitro were also included in the analysis to facilitate the detection of in planta-specific transcripts and to identify TDFs differentially expressed among races/strains. Conclusion: Our data suggest that resistance against FOM in melon involves only limited transcriptional changes, and that wilting symptoms could derive, at least partially, from an active plant response. We discuss the pathogen-derived transcripts expressed in planta during the infection process and potentially related to virulence functions, as well as transcripts that are differentially expressed between the two FOM races grown in vitro. These transcripts provide candidate sequences that can be further tested for their ability to distinguish between races. Sequence data from this article have been deposited in GenBank, Accession Numbers: HO867279-HO867981

Breve informe por los herederos de Jayme Tribes y Pareja, vecinos de la Villa de Callosa de Segura, en el pleyto que siguen por esta Real Audiencia con los herederos de Don Juan Antonio Ornedal y Maza, Governador que fue de la Ciudad de Cartagena, sobre el riego de cierta heredad : Hecho, y seguida de los Autos.

Sobre el tít.: "[cristus] Jesus, Maria, Joseph, Joaquin, y Ana"Caplletra ornada al començament del textSign.: A-C2Text amb postil·les marginalsReclam