Evaluación bio-económica y calidad de los pastos Carimagua (Andropogón gayanus) y Jaraguá (Hyparrhenia ruffa) a diferentes niveles de fertilización nitrogenada

El presente trabajo de investigación evaluación bio-económica y calidad de los pastos Carimagua (andropogón gayanus) y Jaraguá (Hyparrhenia ruffa) a diferentes niveles de fertilización nitrogenada, se realizó en el Departamento de Ciencias Agronómicas de la Facultad Multidisciplinaria Oriental, localizada en el Cantón El Jute, jurisdicción y departamento de San Miguel. Las coordenadas geográficas del lugar son: 132° 16' latitud Norte y 88° 09 longitud Oeste, con altura sobre el nivel del mar de 140 metros. La realización de éste experimento tiene como propósito conocer el efecto de los diferentes niveles de fertilización nitrogenada utilizando las variables de producción y diferencias bromatológicas, bajo un análisis económico de las especies en estudio. Este experimento se llevó a cabo bajo un diseño estadístico factorial en parcelas divididas, distribuidas en bloques al azar, con 2 factores en estudio, 8 tratamientos y 5 repeticiones. Al realizar los resultados se concluye que la mayor altura de planta (168.53 cm) para la especie Carimagua se logró bajo el tratamiento 120 kg/ha de nitrógeno; mientras que para la espacie Jaraguá la mayor altura de planta (90.47 cm) se logró con el tratamiento 60 kg/ha de nitrógeno; sin embargo bajo estos mismos tratamientos no hubo incremento en peso de materia verde para ambas especies, por lo que se concluye que la mayor altura de plantas en la especie Carimagua se compensa con la mayor población y cantidad de hojas por parte de la especie Ja- raguá, logrando de esta manera pesos semejantes en cuanto a materia verde se refiere. En cuanto a materia seca, no hubo un tratamiento que afectara dicha variable; pero si hubo un incremento para las épocas de corte, las que tuvieron un orden creciente del primer al tercer corte de lo que se concluye que a medida el invierno declina disminuye la cantidad de humedad en las plantas, lo que permite un aumento en la cantidad de materia seca. Al analizar el porcentaje de grasa en los 3 cortes se observó que fue mayor en el segundo corte. Para la variable cenizas hubo disminución del primer al tercer corte, atribuyéndole esto a la disminución del número de hojas presentes en las especies en estudio. El porcentaje de fibra cruda fue mayor para el primer corte y no hubo ninguna influencia de los tratamientos de Nitrógeno sobre esta variable en estudio. El contenido de Carbohidratos presentó una variación creciente de la primera a la última época de corte, aumento que se debió al mayor tiempo de establecimiento de las especies

Identification of O-mannosylated Virulence Factors in Ustilago maydis

The O-mannosyltransferase Pmt4 has emerged as crucial for fungal virulence in the animal pathogens Candida albicans or Cryptococcus neoformans as well as in the phytopathogenic fungus Ustilago maydis. Pmt4 O-mannosylates specific target proteins at the Endoplasmic Reticulum. Therefore a deficient O-mannosylation of these target proteins must be responsible for the loss of pathogenicity in pmt4 mutants. Taking advantage of the characteristics described for Pmt4 substrates in Saccharomyces cerevisiae, we performed a proteome-wide bioinformatic approach to identify putative Pmt4 targets in the corn smut fungus U. maydis and validated Pmt4-mediated glycosylation of candidate proteins by electrophoretic mobility shift assays. We found that the signalling mucin Msb2, which regulates appressorium differentiation upstream of the pathogenicity-related MAP kinase cascade, is O-mannosylated by Pmt4. The epistatic relationship of pmt4 and msb2 showed that both are likely to act in the same pathway. Furthermore, constitutive activation of the MAP kinase cascade restored appressorium development in pmt4 mutants, suggesting that during the initial phase of infection the failure to O-mannosylate Msb2 is responsible for the virulence defect of pmt4 mutants. On the other hand we demonstrate that during later stages of pathogenic development Pmt4 affects virulence independently of Msb2, probably by modifying secreted effector proteins. Pit1, a protein required for fungal spreading inside the infected leaf, was also identified as a Pmt4 target. Thus, O-mannosylation of different target proteins affects various stages of pathogenic development in U. maydis

The General Transcriptional Repressor Tup1 Is Required for Dimorphism and Virulence in a Fungal Plant Pathogen

A critical step in the life cycle of many fungal pathogens is the transition between yeast-like growth and the formation of filamentous structures, a process known as dimorphism. This morphological shift, typically triggered by multiple environmental signals, is tightly controlled by complex genetic pathways to ensure successful pathogenic development. In animal pathogenic fungi, one of the best known regulators of dimorphism is the general transcriptional repressor, Tup1. However, the role of Tup1 in fungal dimorphism is completely unknown in plant pathogens. Here we show that Tup1 plays a key role in orchestrating the yeast to hypha transition in the maize pathogen Ustilago maydis. Deletion of the tup1 gene causes a drastic reduction in the mating and filamentation capacity of the fungus, in turn leading to a reduced virulence phenotype. In U. maydis, these processes are controlled by the a and b mating-type loci, whose expression depends on the Prf1 transcription factor. Interestingly, Δtup1 strains show a critical reduction in the expression of prf1 and that of Prf1 target genes at both loci. Moreover, we observed that Tup1 appears to regulate Prf1 activity by controlling the expression of the prf1 transcriptional activators, rop1 and hap2. Additionally, we describe a putative novel prf1 repressor, named Pac2, which seems to be an important target of Tup1 in the control of dimorphism and virulence. Furthermore, we show that Tup1 is required for full pathogenic development since tup1 deletion mutants are unable to complete the sexual cycle. Our findings establish Tup1 as a key factor coordinating dimorphism in the phytopathogen U. maydis and support a conserved role for Tup1 in the control of hypha-specific genes among animal and plant fungal pathogens

New insights into the evolutionary conservation of the sole PIKK pseudokinase Tra1/TRRAP

International audienc

The hos2 histone deacetylase controls Ustilago maydis virulence through direct regulation of mating-type genes

This is an open access article distributed under the terms of the Creative Commons Attribution License.Morphological changes are critical for host colonisation in plant pathogenic fungi. These changes occur at specific stages of their pathogenic cycle in response to environmental signals and are mediated by transcription factors, which act as master regulators. Histone deacetylases (HDACs) play crucial roles in regulating gene expression, for example by locally modulating the accessibility of chromatin to transcriptional regulators. It has been reported that HDACs play important roles in the virulence of plant fungi. However, the specific environment-sensing pathways that control fungal virulence via HDACs remain poorly characterised. Here we address this question using the maize pathogen Ustilago maydis. We find that the HDAC Hos2 is required for the dimorphic switch and pathogenic development in U. maydis. The deletion of hos2 abolishes the cAMP-dependent expression of mating type genes. Moreover, ChIP experiments detect Hos2 binding to the gene bodies of mating-type genes, which increases in proportion to their expression level following cAMP addition. These observations suggest that Hos2 acts as a downstream component of the cAMP-PKA pathway to control the expression of mating-type genes. Interestingly, we found that Clr3, another HDAC present in U. maydis, also contributes to the cAMP-dependent regulation of mating-type gene expression, demonstrating that Hos2 is not the only HDAC involved in this control system. Overall, our results provide new insights into the role of HDACs in fungal phytopathogenesis.This work was funded by BIO2010-16787 and BIO2013–48858—P from MICIN and MEC from Spain, by an ATIP-Avenir Grant from the CNRS, a Marie Curie Actions Career Integration Grants (FP7-PEOPLE-2012-CIG/COACTIVATOR), and the Centre National de la Recherche Scientifique (CNRS) to DH. AEV was supported by a Postdoctoral Fellowship from the Fondation pour la Recherche Médicale (SPF20130526854).Peer Reviewe

Protein glycosylation in the phytopathogen Ustilago maydis: From core oligosaccharide synthesis to the ER glycoprotein quality control system, a genomic analysis

The corn smut fungus Ustilago maydis has, over recent decades, become established as a robust pathogenic model for studying fungi–plant relationships. This use of U. maydis can be attributed to its biotrophic host interaction, easy culture and genetic manipulation in the laboratory, and the severe disease symptoms it induces in infected maize. Recent studies have shown that normal protein glycosylation is essential for pathogenic development, but dispensable for the saprophytic growth or mating. Given the relevance of protein glycosylation for U. maydis virulence, and consequently its role in the plant pathogenesis, here we review the main actors and events implicated in protein glycosylation. Furthermore, we describe the results of an in silico search, where we identify all the conserved members of the N- and O-glycosylation pathways in U. maydis at each stage: core oligosaccharide synthesis, addition of the core oligosaccharide to nascent target proteins, maturation and extension of the core oligosaccharide, and the quality control system used by the cell to avoid the presence of unfolded glycoproteins. Finally, we discuss how these genes could affect U. maydis virulence and their biotechnological implications.This work was supported by Ministerio de Ciencia e Innovación Grant BIO2007-60531. A.F.A and A.E.V were supported by fellowships from Ministerio de Ciencia e Innovación. CABD is institutionally supported by CSIC, Universidad Pablo de Olavide and the Junta de Andalucía.Peer Reviewe

The requirement for protein O-mannosylation for Ustilago maydis virulence seems to be linked to intrinsic aspects of the infection process rather than an altered plant response

Article Addendum.Fungal plant pathogenesis involves complex crosstalk between fungi and their plant hosts. In the case of biotrophic fungi, the host interaction is finely controlled to maintain plant viability during infection since the fungus depends on the survival of colonized plant cells. Many proteins which participate in this process are thought to be glycosylated. Thus, defects in the glycosylation of fungal proteins might alter the normally attenuated plant response and consequently affect fungal progression. O-mannosyltransferases are responsible for adding mannose residues onto target proteins, with each O-mannosyltransferase having individual target specificities. In an earlier study, we showed that O-mannosylation is essential for Ustilago maydis virulence. We found that the loss of O-mannosyltransferase PMT4 was associated with a reduced formation frequency of the invasive morphogenic structure known as the appressorium, combined with a loss in their ability to penetrate plant cuticle. Here, we discuss the possible molecular causes of these phenotypes and present additional evidence, which argue against an alteration of plant response to fungal infection as the primary cause of the Δpmt4 phenotype.This work was supported by Ministerio de Ciencia e Innovación Grant BIO2007-60531. A.F.A. and A.E.V. were supported by fellowships from Ministerio de Ciencia e Innovación. CABD is institutionally supported by CSIC, Universidad Pablo de Olavide and Junta de Andalucía.Peer reviewe

La O-manosiltransferasa PMT4 es un nuevo factor esencial para el desarrollo de la estructura morfogénica del apresorio en Ustilago maydis

Resumen del póster presentado al XXXVII Congreso de la Sociedad Española de Genética, celebrado en Torremolinos (Málaga) del 29 de septiembre al 2 de octubre de 2009.Muchos hongos fitopatógenos consiguen superar el problema de la penetración de la cutícula de la planta desarrollando una estructura especializada conocida como apresorio. Este cambio morfogenético depende de numerosos factores en gran parte, dependientes de proteínas secretadas y constitutivas de la pared celular. Muchas de estas proteínas son glicosiladas, esto es, un tipo de modificación postraduccional que, en muchos casos, es relevante para la estabilidad, localización y función final de las proteínas. La O-manosilación es un tipo conservado de glicosilación que está involucrado en un amplio rango de procesos. Sin embargo, ni el papel de esta importante clase de glicosilación, ni sus componentes enzimáticos han sido caracterizados en hongos fitopatógenos. En Saccharomyces cerevisiae, las familias de proteínas PMT, KRE2/MNT1 y MNN1 catalizan cada paso de la ruta de O-manosilación añadiendo secuencialmente manosas a sus proteínas diana. Nosotros hemos identificado todos los miembros de estas tres familias y analizado su papel en la patogénesis de Ustilago maydis, responsable de la enfermedad del carbón del maíz. Además, mostramos que PMT4, uno de los tres miembros de la familia PMT en U. maydis es esencial para la formación de tumores en la planta. La proteína PMT4 parece ser sólo requerida para la patogénesis y dispensable para otros aspectos del ciclo de vida de U. maydis. En nuestro estudio mostramos que la deleción de pmt4 supone una fuerte reducción en la frecuencia de formación de apresorios y los pocos apresorios formados han perdido la capacidad de penetrar la cutícula vegetal. Nuestras observaciones sugieren que la ruta de O-manosilación es una modificación postraduccional que juega un papel clave en el desarrollo patogénico de U. maydis. Además, el hecho de la alta especificidad de una única Omanosiltrasferasa nos ha hecho iniciar la búsqueda de proteínas diana de PMT4 involucradas en la patogénesis, permitiendo avanzar en el conocimiento de la interacción hongo-planta y desarrollar nuevas estrategias para el control fúngico.Peer reviewe