The height of a white-light flare and its hard X-ray sources

We describe observations of a white-light flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray sources.For this purpose we use hard X-ray images from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), and optical images at 6173 \AA from the Solar Dynamics Observatory (SDO). We find that the centroids of the impulsive-phase emissions in white light and hard X-rays (30-80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0.2". This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions, as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 \AA image from the Solar-Terrestrial RElations Observatory (STEREO-B) spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; \tau = 1 at 5000 \AA) of 305 \pm 170 km and 195 \pm 70 km, respectively, for the centroids of the hard X-ray (HXR) and white light (WL) footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of \tau = 1 for the 6173 \AA and the ~40 keV photons observed, respectively.Comment: Accepted in ApJ Letters, 8 pages, 4 figure

Presente e futuro da virología vegetal no Brasil

No Brasil, a virología vegetal hoje representa urna área de destaque dentro da fitopatología, pelo número de especialistas ativos e sua produgáo científica, em termos de quantidade e qualidade.Academia Nacional de Agronomía y Veterinari

Presente e futuro da virología vegetal no Brasil

No Brasil, a virología vegetal hoje representa urna área de destaque dentro da fitopatología, pelo número de especialistas ativos e sua produgáo científica, em termos de quantidade e qualidade.Academia Nacional de Agronomía y Veterinari

Presente e futuro da virología vegetal no Brasil

No Brasil, a virología vegetal hoje representa urna área de destaque dentro da fitopatología, pelo número de especialistas ativos e sua produgáo científica, em termos de quantidade e qualidade.Academia Nacional de Agronomía y Veterinari

An annotated list of ornamentals naturally found infected by Brevipalpus mite-transmitted viruses

Os primeiros casos de plantas ornamentais encontradas naturalmente infetadas por vírus transmitidos por Brevipalpus (Acari: Tenuipalpidae) (VTB) foram registrados nos anos 1990 na região de Piracicaba, Estado de São Paulo, e ocorrências subseqüentes foram observadas em várias outras regiões do país e de outros países das Américas. Atualmente acham-se relatadas 37 espécies de ornamentais (para efeito de simplificação, orquídeas foram consideradas como única espécie) pertencentes a 18 famílias botânicas. Pelo fato de causarem apenas infecções localizadas, geralmente nas folhas, VTB em ornamentais não causam preocupações aos produtores, mas potencialmente podem causar perdas econômicas se ocorrerem explosões populacionais do ácaro vetor. Plantas ornamentais podem servir de reservatório de VTB de importância econômica como os vírus da leprose dos citros-tipo citoplasmático (CiLV-C), da mancha verde do maracujá (PFGSV) e da mancha anular do cafeeiro (CoRSV).The first cases of ornamental plants found infected by Brevipalpus transmitted viruses (BTV) were described in the 1990's from the region of Piracicaba, State of São Paulo, Brazil; subsequent cases were from other regions in the country and other American countries. Currently, 37 ornamental plant species (for the sake of simplicity, orchids being considered as a single species), belonging to 18 families of dicotyledons, have been reported hosting BTV. Because of the non systemic type of infection of these viruses, the localized diseases they cause are unimportant usually, but they have the potential to cause economic losses if severe outbreaks of Brevipalpus mite populations occur. Some ornamentals may serve as reservoirs to BTV known to cause serious damage to food crops as Citrus leprosis virus- cytoplasmic type (CiLV-C), passion fruit green spot virus (PFGSV) and Coffee ringspot virus (CoRSV)

Levantamento preliminar de viroses de plantas cultivadas nos arredores de Manaus, Am

Um levantamento preliminar de viroses de plantas cultivadas nos arredores de Manaus foi feito em março de 1977. Diversas propriedades particulares e campos experimentais foram inspecionados, anotando-se as plantas exibindo sintomatologia suspeita. A verificação da sua possível etiologia viral foi feita através de testes de transmissão, serologia e exames electrono microscópicos. Foram constatadas diversas viroses em tomateiro, pimentão, quiabeiro, feijoeiro, cucurbitáceas, soja, feijão-de-asa, milho. etc. Como regra geral, ao contrário do que sucede no Sul do País, as viroses transmitidas por afídeos foram de ocorrência rara, presumivelmente porque as condições climáticas da região seriam desfavoráveis à biologia desses insetos

Rescue of a Cilevirus from infectious cDNA clones

[EN] Reverse genetics systems represent an important tool for studying the molecular and functional processes of viral infection. Citrus leprosis virus C (CiLV-C) (genus Cilevirus, family Kitaviridae) is the main pathogen responsible for the citrus leprosis (CL) disease in Latin America, one of the most economically important diseases of the citrus industry. Molecular studies of this pathosystem are limited due to the lack of infectious clones. Here, we report the construction and validation of a CiLV-C infectious cDNA clone based on an agroinfection system. The two viral RNA segments (RNA1 and RNA2) were assembled into two binary vectors (pJL89 and pLXAS). Agro-infiltrated Nicotiana benthamiana plants showed a response similar to that observed in the natural infection process with the formation of localized lesions restricted to the inoculated leaves. The virus recovered from the plant tissue infected with the infectious clones can be mechanically transmitted between N. benthamiana plants. Detection of CiLV-C subgenomic RNAs (sgRNAs) from agroinfiltrated and mechanically inoculated leaves further confirmed the infectivity of the clones. Finally, partial particle-purification preparations or sections of CiLV-C-infected tissue followed by transmission electron microscopy (TEM) analysis showed the formation of CiLV-C virions rescued by the infectious clone. The CiLV-C reverse genetic system now provides a powerful molecular tool to unravel the peculiarities of the CL pathosystem.This work was supported by grant PID2020-115571RB-100 from the Spanish MCIN/AEI/10.13039/501100011033 granting agency.Leastro, MO.; Kitajima, EW.; Pallás Benet, V.; Sanchez Navarro, JA. (2024). Rescue of a Cilevirus from infectious cDNA clones. Virus Research. 339. https://doi.org/10.1016/j.virusres.2023.19926433

Membrane Association and Topology of Citrus Leprosis Virus C2 Movement and Capsid Proteins

[EN] Although citrus leprosis disease has been known for more than a hundred years, one of its causal agents, citrus leprosis virus C2 (CiLV-C2), is poorly characterized. This study described the association of CiLV-C2 movement protein (MP) and capsid protein (p29) with biological membranes. Our findings obtained by computer predictions, chemical treatments after membrane fractionation, and biomolecular fluorescence complementation assays revealed that p29 is peripherally associated, while the MP is integrally bound to the cell membranes. Topological analyses revealed that both the p29 and MP expose their N- and C-termini to the cell cytoplasmic compartment. The implications of these results in the intracellular movement of the virus were discussed.This work was supported by Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), proc. 2014/0845-9, 2017/50222-0, 2015/10249-1 and 2017/19898-8. This work was also supported by grant BIO2017-88321-R from the Spanish Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER), and the Prometeo Program GV2015/010 from the Generalitat Valenciana.Oliveira Leastro, M.; Freitas-Astua, J.; Watanabe Kitajima, E.; Pallás Benet, V.; Sanchez Navarro, JA. (2021). Membrane Association and Topology of Citrus Leprosis Virus C2 Movement and Capsid Proteins. Microorganisms. 9(2):1-9. https://doi.org/10.3390/microorganisms9020418199