Publications

3807

The major citrus area of Brazil occupies near 450,000 ha between the Triângulo Mineiro (TM) region of Minas Gerais State and the south of São Paulo State (SPS). Significant climatic variation occurs between regions which could affect huanglongbing (HLB) progress, which is lower in TM. To investigate this possibility, young sweet orange shoots were sampled periodically over 2 years to determine ‘Candidatus Liberibacter asiaticus’ titers in naturally infected trees in orchards in Analândia, central SPS, and Frutal and Comendador Gomes, within TM. Data-loggers recorded local temperature and relative humidity hourly. In the laboratory, five ‘Ca. L. asiaticus’-free Diaphorina citri adults were placed on each sampled shoot for 48 h to feed and acquire the pathogen. Shoots and insects were individually analyzed by quantitative polymerase chain reaction to determine ‘Ca. L. asiaticus’ titers. The incidence of ‘Ca. L. asiaticus’-positive shoots, ‘Ca. L. asiaticus’ titers, and acquisition rates were lower for shoots from Comendador Gomes than those from Frutal or Analândia. Stronger association was observed between ‘Ca. L. asiaticus’ titers and the number of hours below 15°C (h < 15°C) or above 30°C (h > 30°C), and cumulative rainfall registered during the 15 days prior to sampling of shoots on each occasion. ‘Ca. L. asiaticus’ titers associated positively with h < 15°C and rainfall and negatively with h > 30°C. The slower spread and lower incidence of HLB in TM may be related to lower incidences of ‘Ca. L. asiaticus’-positive young shoots and lower titers of ‘Ca. L. asiaticus’ in the same shoots as a consequence of the warmer and drier conditions.

AbstractThe global deep subsurface biosphere is one of the largest reservoirs for microbial life on our planet. This study takes advantage of new sampling technologies and couples them with improvements to DNA sequencing and associated informatics tools to reconstruct the genomes of uncultivated Bacteria and Archaea from fluids collected deep within the Juan de Fuca Ridge subseafloor. Here, we generated two metagenomes from borehole observatories located 311 meters apart and, using binning tools, retrieved 98 genomes from metagenomes (GFMs). Of the GFMs, 31 were estimated to be >90% complete, while an additional 17 were >70% complete. Phylogenomic analysis revealed 53 bacterial and 45 archaeal GFMs, of which nearly all were distantly related to known cultivated isolates. In the GFMs, abundant Bacteria included Chloroflexi, Nitrospirae, Acetothermia (OP1), EM3, Aminicenantes (OP8), Gammaproteobacteria, and Deltaproteobacteria, while abundant Archaea included Archaeoglobi, Bathyarchaeota (MCG), and Marine Benthic Group E (MBG-E). These data are the first GFMs reconstructed from the deep basaltic subseafloor biosphere, and provide a dataset available for further interrogation.

El objetivo fue determinar diferencias en la actividad enzimática antioxidante y la concentración de fenoles totales en plantas de limón mexicano (Citrus aurantifolia (Christm.) Swingle), limón persa (Citrus latifolia Tanaka); y naranja dulce Valencia (Citrus sinensis (L.) Osbeck), infectadas bajo condiciones naturales de campo con Candidatus Liberibacter asiaticus (CaLas), en Bustamante, Tamaulipas, México. Se determinó la presencia de CaLas por qPCR; la actividad enzimática de fenilalanina amonio liasa (PAL), que se activa ante el ataque de patógenos; peroxidasa que interviene en la lignificación de paredes como respuesta a la infección; α-amilasa que degrada el almidón y se acumula en el tejido vascular, y compuestos fenólicos que cumplen funciones de defensa. Se realizó un análisis de contrastes. La concentración de proteínas totales mostró diferencias significativas entre especies entre especies (P< 0.0001). Con una media de 6.1 y 6.37 mg de proteínas por g de tejido fresco para árboles infectados de limón mexicano; y naranja dulce negativa a CaLas. La actividad peroxidasa presentó diferencia significativa para limón persa (P=0.0341), con una media de 1.96 U.mg de proteína-<sup>1</sup>. En naranja dulce se observó mayor actividad de α amilasa en los árboles infectados por CaLas (1.19 U.mg de proteína-<sup>1</sup>). La concentración de PAL y fenoles totales no presentaron diferencias significativas entre especies. En el presente estudio se observó que CaLas influye en la actividad enzimática de cítricos.