Phytoplasmas diversity and identification of new aster yellows subgroup (16SrI) associated with weed species in Argentina

Symptoms of phytoplasma infection were observed in different weed species, Bidens subalternans, Conyza bonariensis, Heterosperma ovatifolium and Conium maculatum, collected from diverse geographical regions in Argentina. To confirm the association of phytoplasma infection with symptomatic plants, PCR, RFLP and phylogenetic analyses based on 16S rRNA-encoding sequences were performed. In this work, we report the presence of phytoplasmas from group 16SrVII (subgroup 16VII-B) infecting C. bonariensis and B. subalternans and from group 16SrIII (subgroup 16SrIII-X) B. subalternans, H. ovatifolium, and C. maculatum. Phytoplasmas from the aster yellows group were detected infecting C. bonariensis and B. subalternans. Analysis of 16S rRNA-encoding genes revealed the presence of two distinct operons, rrnB (16SrI-B) and newly described rrnA, which is different from the reference RFLP patterns of all previously established 16SrI-subgroups. A single rp operon sequence analysis reveals the presence of simple infection and confirms a description of a novel subgroup. On the basis of these results we propose a designation of new subgroup 16SrI-(B/AJ) AJ (rp-AJ). To our knowledge, this is the first report of phytoplasmas infecting Bidens subalternans¸ Heterosperma ovatifolium and Conium maculatum.Fil: Fernandez, Franco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; ArgentinaFil: Galdeano, Ernestina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentin

Draft Genome Sequence of " Candidatus Phytoplasma pruni" (X-Disease Group, Subgroup 16SrIII-B) Strain ChTDIII from Argentina

Herein, we report the draft genome sequence of “Candidatus Phytoplasma pruni” strain ChTDIII (subgroup 16SrIII-B). The final assembly consists of 790,517 nucleotides organized in 67 contigs (minimal size, 1 kb), with a G+C content of 29.4% and encoding 672 proteins.Instituto de Patología VegetalFil: Fernandez, Franco Daniel . Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Zübert, Christina. University of Hohenheim. Integrative Infection Biology Crops-Livestock; AlemaniaFil: Huettel, Bruno. Max Planck Genome Centre Cologne. Max Planck Institute for Plant Breeding; AlemaniaFil: Kube, Michael. University of Hohenheim. Integrative Infection Biology Crops-Livestock; AlemaniaFil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conci, Luis Rogelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina

Sistema de gestión de seguridad y salud en el trabajo para disminuir los riesgos en la Empresa NATHANAEL S.A.C., 2020

En el centro del estudio, SERVICIOS E INVERSIONES NATHANAEL S.A.C. tiene como objetivo principal, Aplicar un Sistema de Gestión de Seguridad y Salud en el Trabajo referente a la ley N° 29783 y las normativas establecidas por el gobierno peruano; para la mejora del ambiente laboral e integridad del colaborador, generando el cumplimiento de esta, para minimizar riesgos, que producen un costo a la organización en: reparación y multas por el ente fiscalizador, SUNAFIL. El estudio muestra la metodología a cerca de SST, describiendo el marco legal vigente. También, describe la situación actual de la organización, a través del Check-List (RM-050-2013-TR), teniendo un 41% de cumplimiento, siendo necesario la implementación de un Sistema de Gestión de SST; se halló una totalidad de 80 riesgos mediante la herramienta IPER y el mapa de riesgo en el área de estudios, teniendo mayor significancia los riesgos biológicos y ergonómicos con un 31% y 24% respectivamente, enmarcando la situación actual (SAR CoV-2). Se realizó y se cumplió el Plan Anual de SST, a través de capacitaciones, procedimientos, auditorías, EPP’S, etc; para evaluar el impacto del SG-SST, disminuyendo de manera favorable los riesgos presentes de categoría Intolerable, Importante, Moderado en un 90%, 63%, 64% respectivamente

Molecular detection of Thecaphora frezzi in peanut (Arachis Hypogaea L.) seeds

Thecaphora frezii is the causal agent of peanut smut, important disease in the Argentine production area. The pathogen can be dispersed by kernels, through surface contamination or small lesions. The aim of this work was to design specific primers to develop a Polymerase Chain Reaction assay for the detection of Thecaphora frezii in peanuts kernels. The ITS region of four T. frezii isolates was amplified and sequenced. A consensus sequence was obtained and a pair of primers specific for the pathogen, named TF-2F and TF- 2R, was synthesized. The primers were used for specificity and sensitivity tests. The former test involved a PCR using DNA from T. frezii and other seed-transmitted pathogens (S. rolfsi, S. minor, Fusarium solani and S. sclerotiorum). A 190 bp fragment was obtained for the T. frezii isolates, whereas no amplification was observed for the remaining pathogens. For the sensitivity test, positive results were observed at concentrations up to 3x10-4 pg of the target DNA. The specificity of this method, along with its sensitivity, makes it an important tool for epidemiological studies of peanut smut.Inst. Patología VegetalFil: Cazon, Luis Ignacio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conforto, Erica Cinthia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Paredes, Juan Andrés. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Rago, Alejandro Mario Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria; Argentin

Detection and identification of a novel 16SrXIII subgroup phytoplasma associated with strawberry red leaf disease in Argentina

Strawberry red leaf phytoplasma was found in strawberry plants from production fields in Lules (Tucumán province) and Bella Vista (Corrientes province), Argentina. Characteristic strawberry red leaf symptoms were stunting, young leaves with yellowing at the edges, mature leaves which curled and were reddish at the abaxial face, flower and fruit deformation and death. The pathogen was detected with phytoplasma-universal primer pairs P1/P7 followed by R16F2n/R16R2 as nested primers in 13 diseased plants. Based on RFLP and sequence analysis of the amplified 16S rRNA gene, the phytoplasma was related to the 16SrXIII group (Mexican periwinkle virescence). In silico the RFLP profile of all the samples analysed revealed the presence of a unique pattern, showing that the novel phytoplasma is different from all the phytoplasmas currently composing the 16SrXIII group. The phylogenetic analysis was consistent with RFLP analysis as the strawberry red leaf phytoplasma was grouped within the 16SrXIII group, but formed a particular cluster. On this basis, the Strawberry red leaf phytoplasma associated with strawberry red leaf disease was assigned to a new subgroup, 16SrXIII-F.Fil: Fernandez, Franco Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Meneguzzi, Natalia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Guzman, Fabiana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Kirschbaum, Daniel Santiago. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Famaillá; ArgentinaFil: Conci, Vilma Cecilia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Nome Docampo, Claudia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina. Universidad Católica de Córdoba; Argentin

Declinamiento del paraíso en arbolado urbano de Parera

En los últimos dos años se comenzó a observar en algunas ciudades del norte de La Pampa el amarillamiento y posterior muerte de plantas de paraíso utilizadas en el arbolado urbano. En la localidad de Parera, los responsables del área de espacios públicos se contactaron con la AER INTA Gral. Pico para determinar el origen de estos síntomas. Luego de un análisis preliminar, donde se descartaron agentes causales con sintomatología similar, se decidió enviar muestras al Instituto de Patología Vegetal de INTA situado en la ciudad de Córdoba. El procesamiento de 5 muestras de plantas de diferentes sectores de la localidad de Parera permitió confirmar la presencia de fitoplasmas en todas las muestras analizadas. A continuación se describen los síntomas de la enfermedad, el conocimiento actual respecto a su epidemiología y recomendaciones.AER General PicoFil: Corro Molas, Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil. Agencia de Extensión Rural General Pico; ArgentinaFil: Fernandez, Franco Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Grangetto, Andrea. Municipalidad de Parera, La Pampa; Argentin

‘Ca. Phytoplasma pruni’ and ‘Ca. Phytoplasma meliae’ are affecting plum in Argentina

We report for the first time the presence of phytoplasmas in association with Plum (Prunus domestica) yellowing in Argentina. Molecular analysis of 16S rDNA gene sequence (RFLP, phylogeny) reveals the existence of two different 16Sr-subgroups, 16SrIII-B and novel 16SrXIII-L. These results contribute to a better understanding of the diversity of phytoplasmas associated with Prunus genera in South America.Instituto de Patología VegetalFil: Bongiorno, Vanina Aylén. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Bongiorno, Vanina Aylén. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); ArgentinaFil: Alessio, Florencia Ivette. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Alessio, Florencia Ivette. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); ArgentinaFil: Curzel, Viviana Noemi. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta. Agencia De Extensión Rural Perico; ArgentinaFil: Nome Docampo, Claudia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; Argentina.Fil: Nome Docampo, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); ArgentinaFil: Fernandez, Franco Daniel . Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conci, Luis Rogelio. Consejo Nacional de Investigaciones Científicas y Técnicas.Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina

Avanços no estudo do Amarelamento do Pessegueiro nas diferentes zonas produtoras de Jujuy, Argentina

En Jujuy existen 850 ha de durazneros (Prunus persica L.), alrededor de 800 ha se encuentran en los valles templados, donde hace unos años comenzaron a observarse plantas con síntomas de amarillamiento, enroje-cimiento, enrollamiento y necrosis de hojas, defoliación prematura y acortamiento de entrenudos, incluso muerte de plantas. El agente causal es fitoplasma Argentinean Peach Yellows (ArPY), del subgrupo 16Sr III-B, X-di-sease. La enfermedad se conoce como «amarillamiento del duraznero», una patología en expansión, sin ante-cedentes en el país, de la cual es importante conocer su epidemiología: presencia y dispersión en variedades introducidas y naturalizadas, caracterizar la sintomatología y su variación estacional, lo que es parte de los objetivos de este trabajo. Mediante prospecciones visuales realizadas en la temporada 2018-2019, se estimó la incidencia/prevalencia de esta patología en los valles áridos y templados. En valles áridos y en los valles templados altos no se registraron plantas con síntomas; en los valles templados bajos se visualizaron plantas enfermas de ArPY y su diagnóstico confirmado en el laboratorio. Se observó variación estacional de la sintoma-tología: en primavera las plantas se presentaban parcial o totalmente afectadas, con acortamiento de entrenu-dos, hojas en escoba de bruja, amarillamiento, enrojecimiento y acartuchamiento de hojas basales; en verano el 60 % de ramas sintomáticas de la primavera precedente, muertas o en proceso, sin nuevos síntomas; en otoño muerte de brindillas de ramas sintomáticas y defoliación anticipada. De 25 lotes productivos evaluados en los cultivares Flordaking, Opedepe y Rojo Dos, se determinó una prevalencia del 100 %. Los mayores valo-res de incidencia se registraron en el cultivar Flordaking. En cuanto a la severidad, medida con una escala de 6 grados, del total de plantas prospectadas (8.871), se observaron los mayores grados en plantas de Flordaking, seguidas de Opedepe y Rojo Dos.In Jujuy, there are 850 hectares of peach trees (Prunus persica L.), 800 hectares are found in the temperate valleys, where plants with symptoms of yellowing, redness, leaf curl and necrosis, premature defoliation and shortening of internodes, even plant death, began to be observed a few years ago. The causal agent is Argen-tinean Peach Yellows phytoplasma (ArPY), from the subgroup: 16Sr III-B, X-disease. The disease is called “peach yellows”, and it is an expanding pathology without records in the country. Hence, the objective of this study was to know its epidemiology: presence and dispersion in introduced and naturalized cultivars, character-ization of the symptoms and their seasonal variation. Through visual surveys, the prevalence/incidence of the pathology in arid and temperate valleys was estimated during the past crop cycle. In arid and high temperate valleys, symptomatic plants were no recorded; however, diseased plants were visualized in the low temperate valleys and the diagnosis was confirmed in the laboratory. Seasonal variation of the symptoms was observed, in spring, the plants were partially or totally affected, with shortening of internodes, witches' broom on leaves, yellowing, reddening and stiffening of basal leaves; in summer, symptomatic branches of the previous spring were dead or about to die but without new symptoms; in autumn, there was death of symptomatic twigs and early defoliation. Out of 25 productive lots surveyed, in Flordaking, Opedepe and Rojo Dos cultivars, a preva-lence of 100 % was determined. The incidence in plants was highest in Flordaking. The severity of the disease, using a 6-degree scale, reflected that of a total of 8,871 surveyed plants, the highest degrees of severity were observed in Flordaking plants, followed by Opedepe and, finally, Rojo Dos.Em Jujuy existem 850 ha de pessegueiros (Prunus persica L.), nos vales temperados encontram-se cerca de 800 ha, onde há alguns anos começaram a se observar plantas com sintomas de amarelamento, avermelha-mento, enrolamento e necrose de folhas, desfoliação prematura e encurtamento de entrenós, inclusive morte de plantas. O agente causal é o fitoplasma Argentinean Peach Yellows (ArPY), do subgrupo 16Sr III-B, X-disease. A doença é conhecida como “amarelamento do pessegueiro”, uma patologia em expansão, sem ante-cedentes no país, da qual é importante conhecer sua epidemiologia: presença e dispersão em variedades in-troduzidas e naturalizadas, caracterizar a sintomatologia e sua variação estacional, o que é parte dos objetivos deste trabalho. Mediante avaliações visuais realizadas na temporada 2018-2019, se estimou a incidência/pre-valência desta patologia nos vales áridos e temperados. Em vales áridos e nos vales temperados altos não se registraram plantas com sintomas; nos vales temperados baixos se visualizaram plantas enfermas de ArPY e seu diagnóstico foi confirmado no laboratório. Foi observada variação estacional da sintomatologia: na prima-vera as plantas se apresentavam parcial ou totalmente afetadas, com encurtamento de entrenós, folhas em vassoura de bruxa, amarelamento, avermelhamento e enrolamento de folhas basais; no verão os 60% de ramas sintomáticas da primavera precedente, mortas ou em processo, sem novos sintomas; no outono morte de brin-dilas de ramas sintomáticas e desfoliação antecipada. De 25 lotes produtivos avaliados nas cultivares Florda-king, Opedepe e Rojo Dos, determinou-se uma prevalência de 100%. Os maiores valores de incidência foram registrados na cultivar Flordaking. Em relação à severidade, medida com uma escala de 6 graus, do total de plantas avaliadas (8.871), observaram-se os maiores graus em plantas de 'Flordaking', seguidas de 'Opedepe' e 'Rojo Dos'.Instituto de Patología VegetalFil: Curzel, Viviana Noemi. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Salta. Agencia De Extensión Rural Perico; ArgentinaFil: Curzel, Viviana Noemi. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Cátedra de Fruticultura; Argentina.Fil: Fernandez, Franco Daniel . Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conci, Luis Rogelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFYMA); Argentina.Fil: Bejarano, Noemí. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Cátedra de Fruticultura; Argentina

First report of Xanthomonas prunicola causing bacterial leaf streaks on wheat in Argentina

Since 2018, bacterial-like symptoms, such as leaf streaks were observed on wheat plants (Triticum aestivum L.) in Córdoba province in Argentina, with 1 to 5% of disease incidence. Samples of wheat stem and spike collected in a trial of varieties for summer/autumn sowing in the experimental field of the INTA Marcos Juárez were disinfected, washed and macerated in mortars with sterile distilled water and extracts were streaked on Luria-Bertani (LB) agar. After 48 h incubation at 28 °C, circular, mucoid, convex, and cream colonies were observed and pure cultures were transferred to LB medium for further identification tests. Biochemical tests corroborated the detection of a Gram-negative bacillus. Conventional PCR was performed using DNA isolate from pure cultures and general primers for various species of genera Xanthomonas (Maes 1993) and Pseudomonas (Mulet et al. 2010). An isolate (Arg-1), with cream colored colonies was positive using general primers for Xanthomonas sp (amplified fragment of 444 bp). A bacterial suspension containing 108 CFU mL−1 grown for 48 h on LB medium at 28 °C was injected into three-week-old leaves of wheat plants to fulfill Koch’s postulates. After 5 days, plants showed symptoms of chlorosis, streaks and then necrosis on the leaves. The bacteria were re-isolated from the inoculated plants, showing same symptoms observed in the original plants. Negative control plants, inoculated with sterile water remained without symptoms. The amplified 444 bp fragment described above was sequenced by the Sanger method (GenBank accession OM972662), as well as another 757 bp fragment amplified with universal primers that amplify the partial 16S rDNA gene (GenBank accession OM972661). Analyses of these sequences, as well as the protein profile of the isolate obtained by matrix assisted laser desorption/ionization time of-flight mass spectrometry (MALDI-TOF MS) Bruker Biotyper, allowed to identify only the genus Xanthomonas. With the purpose of determine the species status, the complete genome of isolate Arg-1 was sequenced using Oxford Nanopore Technologies (ONT). Total gDNA was isolate from pure cultures using a commercial kit (Wizard Genomic DNA Purification Kit, Promega). gDNA library was constructed using Ligation Sequencing Kit (SQK-LSK109) and sequenced using ONT platform on a MinION 1kb device. Raw basecalled sequences were filtered using Filtlong and assembled using Trycycler. The genome was assembled in a single contig comprising 5.410.641 bp with 4740 predicted CDSs and 63.9% GC content. Genome sequence was deposited in GenBank under accession number CP094827 and SRA data SRX14635308. Whole-genome Average Nucleotide Identity (ANI) analysis showed values of ~ 97% against the reference genomes of Xanthomonas prunicola (PHKX01.1, PHKV01.1 and PHKW01.1) and 100% in complete 16S rRNA gene sequences (1547 bp). These findings suggest that a new wheat pathogen within the genus Xanthomonas is present in Argentina, as well as was reported in Uruguay and USA (Clavijo et al. 2021). To our knowledge, this is the first report of X. prunicola affecting wheat in Argentina and the first complete genome registered for this specie. Accurate and specific diagnostics are required for the detection of X. prunicola in wheat crops to implement correct prevention and control strategies to this disease, avoiding the dissemination in lots where it has not yet been found.Instituto de Patología VegetalFil: Martino, Julia Andrea. Fondo para la Investigación Científica y Tecnológica (FONCYT); ArgentinaFil: Martino, Julia Andrea. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Fernandez, Franco Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); ArgentinaFil: Pozzi, Elizabeth Alicia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Alberione, Enrique Javier. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Bainotti, Carlos Tomas. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Marquez, Nathalie. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Marquez, Nathalie. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); ArgentinaFil: Tolocka, Patricia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Tolocka, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); ArgentinaFil: Salines, Nicolas. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Gomez, Dionisio Tomas. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Donaire, Guillermo Manuel. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Marcos Juárez; ArgentinaFil: Conci, Luis Rogelio. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Conci, Luis Rogelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); ArgentinaFil: Alemandri, Vanina Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Patología Vegetal; ArgentinaFil: Alemandri, Vanina Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Fitopatología y Modelización Agrícola (UFyMA); Argentin

Class switching and meiotic defects in mice lacking the E3 ubiquitin ligase RNF8

53BP1 is a well-known mediator of the cellular response to DNA damage. Two alternative mechanisms have been proposed to explain 53BP1’s interaction with DNA double-strand breaks (DSBs), one by binding to methylated histones and the other via an RNF8 E3 ligase–dependent ubiquitylation pathway. The formation of RNF8 and 53BP1 irradiation-induced foci are both dependent on histone H2AX. To evaluate the contribution of the RNF8-dependent pathway to 53BP1 function, we generated RNF8 knockout mice. We report that RNF8 deficiency results in defective class switch recombination (CSR) and accumulation of unresolved immunoglobulin heavy chain–associated DSBs. The CSR DSB repair defect is milder than that observed in the absence of 53BP1 but similar to that found in H2AX−/− mice. Moreover, similar to H2AX but different from 53BP1 deficiency, RNF8−/− males are sterile, and this is associated with defective ubiquitylation of the XY chromatin. Combined loss of H2AX and RNF8 does not cause further impairment in CSR, demonstrating that the two genes function epistatically. Importantly, although 53BP1 foci formation is RNF8 dependent, its binding to chromatin is preserved in the absence of RNF8. This suggests a two-step mechanism for 53BP1 association with chromatin in which constitutive loading is dependent on interactions with methylated histones, whereas DNA damage–inducible RNF8-dependent ubiquitylation allows its accumulation at damaged chromatin