Interactions of maize bushy stunt phytoplasma with the leafhopper vector, Dalbulus maidis (Delong and Wolcott) (Hemiptera: Cicadellidae) and associated microbiota

Phytoplasmas are bacteria with a persistent propagative transmission by insect vectors that generates direct and indirect interactions among them. In order to understand these interactions for maize bushy stunt phytoplasma (MBSP) and the leafhopper vector Dalbulus maidis (Hemiptera: Cicadellidae), two research lines were addressed. The first one aimed to determine the indirect effects of maize infection by MBSP on some biological and behavioral parameters of the vector, whereas a second line investigated direct interactions of the phytoplasma with D. maidis during its movement through the vector body following acquisition from plants, and associated microbiota. Indirect effects were investigated in choice experiments in which alighting and oviposition preferences by D. maidis were compared on healthy vs. MBSP-infected plants with variable incubation time (diseased plants with early and advanced symptoms, or still asymptomatic). Likewise, indirect effect of MBSP on the D. maidis biology was determined in two life table experiments in which the vector was reared on healthy vs. MBSP-infected plants expressing advanced disease symptoms or still asymptomatic. Choice experiments showed that alighting and oviposition preferences of D. maidis on MBSP-infected plants compared to healthy plants depend on the pathogen incubation period in the plant. The leafhopper preferred MBSP-infected plants over healthy ones during the asymptomatic phase of the disease, but rejected infected plants with advanced symptoms. The vector was able to acquire MBSP from asymptomatic infected plants shortly (3 days) after inoculation, but transmission efficiency increased when acquisition occurred at later stages of the pathogen incubation period (≥14 days) in the source plants and the test plants showed disease symptoms faster. These results suggest that MBSP modulates D. maidis preference for asymptomatic infected plants in the early stages of the crop, allowing rapid spread of this pathogen. Maize infection by the phytoplasma had a neutral effect on most life table parameters of D. maidis; a lower net reproductivity rate (Ro) was observed in the cohort reared on MBSP-infected plants with advanced symptoms, which was compensated to some extent by a higher sexual ratio. MBSP acquisition by all vector nymphal stadia was confirmed by PCR, and the pathogen as detected in both male and female reproductive organs. Concerning direct MBSP-vector interactions, transmission electron microscopy analyses showed phytoplasma-like cells in the midgut lumen, microvilli and epithelial cells, suggesting that MBSP enters the epithelium midgut through the microvilli wall. Within the epithelial cells, mitochondria and bacteria-like cells (possibly endosymbionts) were observed together with masses of phythoplasma-like cells. In the hemocoel, phytoplasma-like cells grouped into a matrix were also observed in association with bacteria-like cells similar to those observed in the midgut epithelium. Similar associations were found in the salivary gland. Interestingly, in-situ hybridization (FISH) technique revealed a variation in diversity and abundance of the microbiota in intestine and salivary glands of D. maidis adults over time after MBSP acquisition from plants. Sulcia sp., Cardinium sp. and eubacteria increased their abundance over time, whereas Rickettsia sp. decreased. The frequent association of the vector microbiota with the phytoplasma in some tissues of D. maidis suggests that endosymbiotic bacteria may play some role in MBSP-vector interactions.

Análise da estrutura populacional e do desequilíbrio de ligação de um painel de acessos de sorgo: uma abordagem usando teoria da coalescência

A estrutura populacional e o desequilíbrio de ligação são dois processos fundamentais para estudos evolutivos e de mapeamento associativo. Tradicionalmente, ambos têm sido investigados por meio de métodos clássicos comumente utilizados. Tais métodos certamente forneceram grandes avanços no entendimento dos processos evolutivos das espécies. No entanto, em geral, nenhum deles utiliza uma visão genealógica de forma a considerar eventos genéticos ocorridos no passado, dificultando a compreensão dos padrões de variação observados no presente. Uma abordagem que possibilita a investigação retrospectiva com base no atual polimorfismo observado é a teoria da coalescência. Assim, o objetivo deste trabalho foi analisar, com base na teoria da coalescência, a estrutura populacional e o desequilíbrio de ligação de um painel mundial de acessos de sorgo (Sorghum bicolor). Para tanto, análises de mutação, migração com fluxo gênico e recombinação foram realizadas para cinco regiões genômicas relacionadas à altura de plantas e maturidade (Dw1, Dw2, Dw4, Ma1 e Ma3) e sete populações previamente selecionadas. Em geral, elevado fluxo gênico médio (Μ = m/μ = 41,78 − 52,07) foi observado entre as populações considerando cada região genômica e todas elas simultaneamente. Os padrões sugeriram intenso intercâmbio de acessos e história evolutiva específica para cada região genômica, mostrando a importância da análise individual dos locos. A quantidade média de migrantes por geração (Μ) não foi simétrica entre pares recíprocos de populações, de acordo com a análise individual e simultânea das regiões. Isso sugere que a forma pela qual as populações se relacionaram e continuam interagindo evolutivamente não é igual, mostrando que os métodos clássicos utilizados para investigar estrutura populacional podem ser insatisfatórios. Baixas taxas médias de recombinação (ρL = 2Ner = 0,030 − 0,246) foram observadas utilizando o modelo de recombinação constante ao longo da região. Baixas e altas taxas médias de recombinação (ρr = 2Ner = 0,060 − 3,395) foram estimadas utilizando o modelo de recombinação variável ao longo da região. Os métodos tradicional (r2) e via coalescência (E[r2 rhomap]) utilizados para a estimação do desequilíbrio de ligação mostraram resultados próximos para algumas regiões genômicas e populações. No entanto, o r2 sugeriu padrões descontínuos de desequilíbrio em várias ocasiões, dificultando o entendimento e a caracterização de possíveis blocos de associação. O método via coalescência (E[r2 rhomap]) forneceu resultados que pareceram ter sido mais consistentes, podendo ser uma estratégia eventualmente importante para um refinamento dos padrões não-aleatórios de associação. Os resultados aqui encontrados sugerem que o mapeamento genético a partir de um único pool gênico pode ser insuficiente para detectar associações causais importantes para características quantitativas em sorgo.

Field and laboratory performance evaluation of a field-blended rubber asphalt.

ALICE is one of four major experiments of particle accelerator LHC installed in the European laboratory CERN. The management committee of the LHC accelerator has just approved a program update for this experiment. Among the upgrades planned for the coming years of the ALICE experiment is to improve the resolution and tracking efficiency maintaining the excellent particles identification ability, and to increase the read-out event rate to 100 KHz. In order to achieve this, it is necessary to update the Time Projection Chamber detector (TPC) and Muon tracking (MCH) detector modifying the read-out electronics, which is not suitable for this migration. To overcome this limitation the design, fabrication and experimental test of new ASIC named SAMPA has been proposed . This ASIC will support both positive and negative polarities, with 32 channels per chip and continuous data readout with smaller power consumption than the previous versions. This work aims to design, fabrication and experimental test of a readout front-end in 130nm CMOS technology with configurable polarity (positive/negative), peaking time and sensitivity. The new SAMPA ASIC can be used in both chambers (TPC and MCH). The proposed front-end is composed of a Charge Sensitive Amplifier (CSA) and a Semi-Gaussian shaper. In order to obtain an ASIC integrating 32 channels per chip, the design of the proposed front-end requires small area and low power consumption, but at the same time requires low noise. In this sense, a new Noise and PSRR (Power Supply Rejection Ratio) improvement technique for the CSA design without power and area impact is proposed in this work. The analysis and equations of the proposed circuit are presented which were verified by electrical simulations and experimental test of a produced chip with 5 channels of the designed front-end. The measured equivalent noise charge was <550e for 30mV/fC of sensitivity at a input capacitance of 18.5pF. The total core area of the front-end was 2300?m × 150?m, and the measured total power consumption was 9.1mW per channel.

Noise and PSRR improvement technique for TPC readout front-end in CMOS. technology.

ALICE is one of four major experiments of particle accelerator LHC installed in the European laboratory CERN. The management committee of the LHC accelerator has just approved a program update for this experiment. Among the upgrades planned for the coming years of the ALICE experiment is to improve the resolution and tracking efficiency maintaining the excellent particles identification ability, and to increase the read-out event rate to 100 KHz. In order to achieve this, it is necessary to update the Time Projection Chamber detector (TPC) and Muon tracking (MCH) detector modifying the read-out electronics, which is not suitable for this migration. To overcome this limitation the design, fabrication and experimental test of new ASIC named SAMPA has been proposed . This ASIC will support both positive and negative polarities, with 32 channels per chip and continuous data readout with smaller power consumption than the previous versions. This work aims to design, fabrication and experimental test of a readout front-end in 130nm CMOS technology with configurable polarity (positive/negative), peaking time and sensitivity. The new SAMPA ASIC can be used in both chambers (TPC and MCH). The proposed front-end is composed of a Charge Sensitive Amplifier (CSA) and a Semi-Gaussian shaper. In order to obtain an ASIC integrating 32 channels per chip, the design of the proposed front-end requires small area and low power consumption, but at the same time requires low noise. In this sense, a new Noise and PSRR (Power Supply Rejection Ratio) improvement technique for the CSA design without power and area impact is proposed in this work. The analysis and equations of the proposed circuit are presented which were verified by electrical simulations and experimental test of a produced chip with 5 channels of the designed front-end. The measured equivalent noise charge was <550e for 30mV/fC of sensitivity at a input capacitance of 18.5pF. The total core area of the front-end was 2300?m × 150?m, and the measured total power consumption was 9.1mW per channel.