Open Access
Necesidades de formación especializada en Fitopatología de los profesionales de la Sanidad Vegetal
(Phytoma España, 2012) López, María Milagros; Murillo Martínez, Jesús; Producción Agraria; Nekazaritza Ekoizpena
La Fitopatología es la ciencia que estudia las enfermedades de las plantas, que como es bien sabido, constituyen un importante factor limitante de la producción agrícola. Esta ciencia, que trata de la naturaleza, etiología y epidemiología de las enfermedades, estudia asimismo métodos de control de virus, viroides, bacterias, mollicutes, hongos, oomicetos, nematodos y plantas parásitas, por lo que presenta una indudable complejidad que es imposible simplificar. Es necesaria, por lo tanto, una formación especializada en Fitopatología que permita a los profesionales asesorar con conocimiento sobre los diferentes temas, cumpliendo los requisitos de la Directiva 2009/128 CE. Ello obliga a reconocer que los planes de estudio actualmente vigentes en España no proporcionan a los estudiantes la formación que será requerida para el desempeño de sus funciones profesionales en dicho campo y que tanto los fitopatólogos como los organismos públicos y privados, debemos poner todos los medios a nuestro alcance para su mejora.
Open Access
Comparative genomics of native plasmids from plant pathogenic Gammaproteobacteria
(Oxford University Press, 2025-04-01) Urriza Leoz, Miriam; Dimaria, Giulio; Oliveira, Luiz Orlando de; Catara, Vittoria; Murillo Martínez, Jesús; Agronomía, Biotecnología y Alimentación; Agronomia, Bioteknologia eta Elikadura; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Plasmids are key in the evolution and adaptation of plant pathogenic Gammaproteobacteria (PPG), yet their diversity and functional contributions remain underexplored. Here, comparative genomics revealed extensive variation in plasmid size, replicon types, mobility, and genetic content across PPG. Most plasmids are small (< 200 kb), except in Pantoea, exhibiting high coding densities (76% to 78%). Five ancestral replicon types were identifed across multiple orders, indicating vertical descent yet effcient horizontal transfer across taxa, although with limited genetic conservation. Virulence plasmids are widespread (56% to 68%) but differ in virulence gene content across orders: type III effector (T3E) genes are common in Pseudomonas and Xanthomonas, but rare in Enterobacterales and Xylella, aligning with their smaller effector repertoires. Plasmids frequently carry regulatory genes, highlighting their role in bacterial phenotype modulation. Distinct patterns were observed among orders: Enterobacterales plasmids often harbor thiamin biosynthesis operons and transcriptional regulators but lack post-transcriptional regulators, while most Pseudomonas and Xanthomonas plasmids are mobile, enriched in T3E genes, and exhibit high insertion sequence densities, fostering DNA mobility. Resistance to ultraviolet light is common, but not to antimicrobial compounds. These fndings highlight the dynamic role of plasmids in spreading adaptive traits, shaping virulence, and driving the evolution of plant pathogenic bacteria.
Open Access
Expression of the gene for resistance to phaseolotoxin (argK) depends on the activity of genes phtABC in Pseudomonas syringae pv. Phaseolicola
(Public Library of Science, 2012) Aguilera, Selene; Torre Zavala, Susana de la; Hernández Flores, José Luis; Murillo Martínez, Jesús; Bravo, Jaime; Álvarez Morales, Ariel; Producción Agraria; Nekazaritza Ekoizpena
The bacterium Pseudomonas syringae pv. phaseolicola produces phaseolotoxin in a temperature dependent manner, being optimally produced between 18 degrees C and 20 degrees C, while no detectable amounts are present above 28 degrees C. Phaseolotoxin is an effective inhibitor of ornithine carbamoyltransferase (OCTase) activity from plant, mammalian and bacterial sources and causes a phenotypic requirement for arginine. To protect the cell from its own toxin, P. syringae pv. phaseolicola synthesizes a phaseolotoxin-resistant OCTase (ROCT). The ROCT is the product of the argK gene and is synthesized only under conditions leading to phaseolotoxin synthesis. The argK gene is included in a chromosomal fragment named Pht cluster, which contains genes involved in the synthesis of phaseolotoxin. The aim of the present work was to investigate the possible involvement of other genes included in the Pht cluster in the regulation of gene argK. We conducted transcriptional analyses of argK in several mutants unable to produce phaseolotoxin, transcriptional fusions and electrophoretic mobility shift assays, which allowed us to determine that genes phtABC, located within the Pht cluster, participate in the transcriptional repression of gene argK at temperatures not permissive for phaseolotoxin biosynthesis. This repression is mediated by a protein present in both toxigenic and nontoxigenic strains of P. syringae and in E. coli, and requires the coordinated participation of phtA, phtB and phtC products in order to carry out an efficient argK repression.
Open Access
La patología vegetal en los últimos 25 años
(Phytoma España, 2013) Murillo Martínez, Jesús; Ortiz Barredo, Amaia; Ayllón, María Ángeles; López, María Milagros; Producción Agraria; Nekazaritza Ekoizpena
En los últimos 25 años hemos asistido a una verdadera revolución de la Ciencia y la Tecnología que, por supuesto, también ha influido de manera importante sobre el desarrollo de la Patología Vegetal. A petición de la editorial Phytoma, en este artículo hemos recogido 25 acontecimientos (avances, logros, riesgos y amenazas) de especial importancia. Indudablemente, la revolución electrónica ha facilitado la comunicación entre investigadores, la diseminación del conocimiento científico y el desarrollo de nuevas técnicas de análisis, entre otras, que han facilitado la generación y análisis de datos. Además, en estos 25 años se han producido diversos avances y acontecimientos que han impactado de forma particular sobre el desarrollo de la Patología Vegetal en España y en el mundo.
Open Access
Detection by multiplex PCR and characterization of nontoxigenic strains of Pseudomonas syringae pv. phaseolicola from different places in Spain. Short communication
(Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), 2006) Rico, A.; Erdozáin García, María; Ortiz Barredo, Amaia; Ruiz de Galarreta, José Ignacio; Murillo Martínez, Jesús; Producción Agraria; Nekazaritza Ekoizpena
El control eficiente de la grasa de la judía causada por Pseudomonas syringae pv. phaseolicola se basa principalmente en la utilización de semilla libre del patógeno. La detección del patógeno en semilla se efectúa mediante métodos altamente sensibles basados en la detección por PCR de los genes responsables de la biosíntesis de la faseolotoxina, la cual, hasta ahora, se consideraba que era sintetizada por todas las cepas del patógeno con importancia epidemiológica. Sin embargo, en la Comunidad de Castilla y León, España, las epidemias de grasa de la judía en campo se asocian frecuentemente con cepas no toxigénicas de P. syringae pv. phaseolicola, que no pueden ser detectadas con los métodos moleculares y serológicos actuales. Los resultados presentados en este trabajo demuestran la existencia de aislados no toxigénicos de P. syringae pv. phaseolicola en zonas distintas de Castilla y León, lo que implica la necesidad de establecer una metodología fiable para la certificación de semillas de judía. Con este propósito, se presenta un sencillo protocolo en dos fases que permite la identificación de los dos tipos de aislados, y que se basa en una PCR multiplex con enriquecimiento a partir de extractos de semilla y en ensayos de patogenicidad.
Open Access
The influence of the accessory genome on bacterial pathogen evolution
(Taylor & Francis, 2011) Jackson, Robert W.; Vinatzer, Boris; Arnold, Dawn L.; Dorus, Steve; Murillo Martínez, Jesús; Producción Agraria; Nekazaritza Ekoizpena
Bacterial pathogens exhibit significant variation in their genomic content of virulence factors. This reflects the abundance of strategies pathogens evolved to infect host organisms by suppressing host immunity. Molecular arms-races have been a strong driving force for the evolution of pathogenicity, with pathogens often encoding overlapping or redundant functions, such as type III protein secretion effectors and hosts encoding ever more sophisticated immune systems. The pathogens’ frequent exposure to other microbes, either in their host or in the environment, provides opportunities for the acquisition or interchange of mobile genetic elements. These DNA elements accessorize the core genome and can play major roles in shaping genome structure and altering the complement of virulence factors. Here, we review the different mobile genetic elements focusing on the more recent discoveries and highlighting their role in shaping bacterial pathogen evolution.
Open Access
Venturia inaequalis resistance in local Spanish cider apple germplasm under controlled and ﬁeld conditions
(Springer, 2012) Martínez Bilbao, Alejandro; Ortiz Barredo, Amaia; Montesinos, Emilio; Murillo Martínez, Jesús; Producción Agraria; Nekazaritza Ekoizpena; Gobierno de Navarra / Nafarroako Gobernua: PA123
Host resistance is a key method for the integrated management of apple scab caused by Venturia inaequalis, which is one of the most important diseases of apple. Artificial inoculation of 92 cider apple cultivars with a mixed inoculum of V. inaequalis identified 19 weakly resistant and 19 resistant cultivars. Twelve of these resistant cultivars were previously classified as having low susceptibility to fire blight, and four of them showed complete or weak resistance to races (1), (1, 6) and (6, 7, 13) of V. inaequalis. The analysis of a selection of 72 cultivars for 6 years under field conditions identified 14 cultivars that were classified as resistant to apple scab under high disease pressure involving one to six Mills periods of severe risk of infection each year. Eight out of these 14 cultivars previously showed high levels of resistance to fire blight, which would allow the incorporation of genetic resistance in the integrated production of cider apples in Spain through their use in breeding programs.
Open Access
Global genomic analysis of Pseudomonas savastanoi pv. savastanoi plasmids
(American Society for Microbiology, 2007) Pérez Martínez, Isabel; Zhao, Youfu; Murillo Martínez, Jesús; Sundin, George W.; Ramos, Cayo; Producción Agraria; Nekazaritza Ekoizpena
Pseudomonas savastanoi pv. savastanoi strains harbor native plasmids belonging to the pPT23A plasmid family (PFPs) which are detected in all pathovars of the related species Pseudomonas syringae examined and contribute to the ecological and pathogenic fitness of their host. However, there is a general lack of information about the gene content of P. savastanoi pv. savastanoi plasmids and their role in the interaction of this pathogen with olive plants. We designed a DNA macroarray containing 135 plasmid-borne P. syringae genes to conduct a global genetic analysis of 32 plasmids obtained from 10 P. savastanoi pv. savastanoi strains. Hybridization results revealed that the number of PFPs per strain varied from one to four. Additionally, most strains contained at least one plasmid (designated non-PFP) that did not hybridize to the repA gene of pPT23A. Only three PFPs contained genes involved in the biosynthesis of the virulence factor indole-3-acetic acid (iaaM, iaaH, and iaaL). In contrast, ptz, a gene involved in the biosynthesis of cytokinins, was found in five PFPs and one non-PFP. Genes encoding a type IV secretion system (T4SS), type IVA, were found in both PFPs and non-PFPs; however, type IVB genes were found only on PFPs. Nine plasmids encoded both T4SSs, whereas seven other plasmids carried none of these genes. Most PFPs and non-PFPs hybridized to at least one putative type III secretion system effector gene and to a variety of additional genes encoding known P. syringae virulence factors and one or more insertion sequence transposase genes. These results indicate that non-PFPs may contribute to the virulence and fitness of the P. savastanoi pv. savastanoi host. The overall gene content of P. savastanoi pv. savastanoi plasmids, with their repeated information, mosaic arrangement, and insertion sequences, suggests a possible role in adaptation to a changing environment.
Open Access
GacA reduces virulence and increases competitiveness in planta in the tumorigenic olive pathogen Pseudomonas savastanoi pv. savastanoi
(Frontiers Media, 2024) Lavado-Benito, Carla; Murillo Martínez, Jesús; Martínez Gil, Marta; Ramos, Cayo; Rodríguez Moreno, Luis; Institute for Multidisciplinary Research in Applied Biology - IMAB
GacS/GacA is a widely distributed two-component system playing an essential role as a key global regulator, although its characterization in phytopathogenic bacteria has been deeply biased, being intensively studied in pathogens of herbaceous plants but barely investigated in pathogens of woody hosts. P. savastanoi pv. savastanoi (Psv) is characterized by inducing tumours in the stem and branches of olive trees. In this work, the model strain Psv NCPPB 3335 and a mutant derivative with a complete deletion of gene gacA were subjected to RNA-Seq analyses in a minimum medium and a medium mimicking in planta conditions, accompanied by RT-qPCR analyses of selected genes and phenotypic assays. These experiments indicated that GacA participates in the regulation of at least 2152 genes in strain NCPPB 3335, representing 37.9 % of the annotated CDSs. GacA also controls the expression of diverse rsm genes, and modulates diverse phenotypes, including motility and resistance to oxidative stresses. As occurs with other P. syringae pathovars of herbaceous plants, GacA regulates the expression of the type III secretion system and cognate effectors. In addition, GacA also regulates the expression of WHOP genes, specifically encoded in P. syringe strains isolated from woody hosts, and genes for the biosynthesis of phytohormones. A gacA mutant of NCPPB 3335 showed increased virulence, producing large immature tumours with high bacterial populations, but showed a significantly reduced competitiveness in planta. Our results further extend the role of the global regulator GacA in the virulence and fitness of a P. syringae pathogen of woody hosts.
Open Access
Sequence diversity of rulA among natural isolates of Pseudomonas syringae and effect on function of rulAB-mediated UV radiation tolerance
(American Society for Microbiology, 2000) Sundin, George W.; Jacobs, Janette L.; Murillo Martínez, Jesús; IdAB. Instituto de Agrobiotecnología / Agrobioteknologiako Institutua
The rulAB locus confers tolerance to UV radiation and is borne on plasmids of the pPT23A family in Pseudomonas syringae. We sequenced 14 rulA alleles from P. syringae strains representing seven pathovars and found sequence differences of 1 to 12% within pathovar syringae, and up to 15% differences between pathovars. Since the sequence variation within rulA was similar to that of P. syringae chromosomal alleles, we hypothesized that rulAB has evolved over a long time period in P. syringae. A phylogenetic analysis of the deduced amino acid sequences of rulA resulted in seven clusters. Strains from the same plant host grouped together in three cases; however, strains from different pathovars grouped together in two cases. In particular, the rulA alleles from P. syringae pv. lachrymans and P. syringae pv. pisi were grouped but were clearly distinct from the other sequenced alleles, suggesting the possibility of a recent interpathovar transfer. We constructed chimeric rulAB expression clones and found that the observed sequence differences resulted in significant differences in UV (wavelength) radiation sensitivity. Our results suggest that specific amino acid changes in RulA could alter UV radiation tolerance and the competitiveness of the P. syringae host in the phyllosphere.