Meiosis is a specialized type of cell division occurring in sexually reproducing organisms to generate haploid cells known as gametes. In flowering plants, male gametes are produced in anthers, being encased in pollen grains. Understanding the genetic regulation of meiosis key events such as chromosome recognition and pairing, synapsis and recombination, is needed to manipulate chromosome associations for breeding purposes, particularly in important cereal crops like wheat. Reverse transcription-quantitative PCR (RT-qPCR) is widely used to analyse gene expression and to validate the results obtained by other transcriptomic analyses, like RNA-seq. Selection and validation of appropriate reference genes for RT-qPCR normalization is essential to obtain reproducible and accurate expression data. In this work, twelve candidate reference genes were evaluated using the mainstream algorithms geNorm, Normfinder, BestKeeper and ΔCt, then ranked from most to least suitable for normalization with RefFinder. Different sets of reference genes were recommended to normalize gene expression data in anther meiosis of bread and durum wheat, their corresponding genotypes in the absence of the Ph1 locus and for comparative studies among wheat genotypes. Comparisons between meiotic (anthers) and somatic (leaves and roots) wheat tissues were also carried out. To the best of our knowledge, our study provides the first comprehensive list of reference genes for robust RT-qPCR normalization to study differentially expressed genes during male meiosis in wheat in a breeding framework. ; This research was supported by grants 201840E046 from the CSIC and AGL2015-64833R from the Spanish Ministerio de Economía y Competitividad (MINECO) and The European Regional Development Fund (FEDER) from the European Union.
Background: During the five decades since their discovery, filoviruses of four species have caused human hemorrhagic fever outbreaks: Marburg (MARV) marburgvirus, and Zaire (EBOV), Sudan (SUDV) and Bundybugyo (BDBV) ebolaviruses. The largest, devastating EBOV epidemic in West Africa in 2014-16, has been followed by outbreaks of MARV in Uganda, 2017, and EBOV in Democratic Republic of Congo, 2018, emphasizing the need to develop preparedness to diagnose all filoviruses. Objectives: The aim of this study was to optimize a new filovirus RT-qPCR to detect all filoviruses, define its limits of detection (LOD) and perform a field evaluation with outbreak samples. Study design: A pan-filovirus RT-qPCR targeting the L gene was developed and evaluated within the EbolaMoDRAD (Ebola virus: modern approaches for developing bedside rapid diagnostics) project. Specificity and sensitivity were determined and the effect of inactivation and PCR reagents (liquid and lyophilized format) were tested. Results: The LODs for the lyophilized pan-filovirus L-RT-qPCR assay were 9.4 copies per PCR reaction for EBOV, 9.9 for MARV, 1151 for SUDV, 65 for BDBV and 289 for Tai Forest virus. The test was set at the Pasteur Institute, Dakar, Senegal, and 83 Ebola patient samples, with viral load ranging from 5 to 5 million copies of EBOV per reaction, were screened. The results for the patient samples were in 100% concordance with the reference EBOVspecific assay. Discussion: Overall, the assay showed good sensitivity and specificity, covered all filoviruses known to be human pathogens, performed well both in lyophilized and liquid-phase formats and with EBOV outbreak clinical samples. ; Peer reviewed
Background During the five decades since their discovery, filoviruses of four species have caused human hemorrhagic fever outbreaks: Marburg (MARV) marburgvirus, and Zaire (EBOV), Sudan (SUDV) and Bundybugyo (BDBV) ebolaviruses. The largest, devastating EBOV epidemic in West Africa in 2014-16, has been followed by outbreaks of MARV in Uganda, 2017, and EBOV in Democratic Republic of Congo, 2018, emphasizing the need to develop preparedness to diagnose all filoviruses. Objectives The aim of this study was to optimize a new filovirus RT-qPCR to detect all filoviruses, define its limits of detection (LOD) and perform a field evaluation with outbreak samples. Study design A pan-filovirus RT-qPCR targeting the L gene was developed and evaluated within the EbolaMoDRAD (Ebola virus: modern approaches for developing bedside rapid diagnostics) project. Specificity and sensitivity were determined and the effect of inactivation and PCR reagents (liquid and lyophilized format) were tested. Results The LODs for the lyophilized pan-filovirus L-RT-qPCR assay were 9.4 copies per PCR reaction for EBOV, 9.9 for MARV, 1151 for SUDV, 65 for BDBV and 289 for Taï Forest virus. The test was set at the Pasteur Institute, Dakar, Senegal, and 83 Ebola patient samples, with viral load ranging from 5 to 5 million copies of EBOV per reaction, were screened. The results for the patient samples were in 100% concordance with the reference EBOV-specific assay. Discussion Overall, the assay showed good sensitivity and specificity, covered all filoviruses known to be human pathogens, performed well both in lyophilized and liquid-phase formats and with EBOV outbreak clinical samples.
The ongoing evolution of microbial pathogens represents a significant issue in diagnostic PCR/qPCR. Many assays are burdened with false negativity due to mispriming and/or probe-binding failures. Therefore, PCR/qPCR assays used in the laboratory should be periodically re-assessed in silico on public sequences to evaluate the ability to detect actually circulating strains and to infer potentially escaping variants. In the work presented we re-assessed a RT-qPCR assay for the universal detection of influenza A (IA) viruses currently recommended by the European Union Reference Laboratory for Avian Influenza. To this end, the primers and probe sequences were challenged against more than 99,000 M-segment sequences in five data pools. To streamline this process, we developed a simple algorithm called the SequenceTracer designed for alignment stratification, compression, and personal sequence subset selection and also demonstrated its utility. The re-assessment confirmed the high inclusivity of the assay for the detection of avian, swine and human pandemic H1N1 IA viruses. On the other hand, the analysis identified human H3N2 strains with a critical probe-interfering mutation circulating since 2010, albeit with a significantly fluctuating proportion. Minor variations located in the forward and reverse primers identified in the avian and swine data were also considered.
The current gold standard technique for SARS-CoV-2 diagnostics is hydrolysis probe-based RT-qPCR. Reliable testing requires reliable control reagents to monitor the efficiency of RNA extraction, reverse transcription and PCR amplification. Here we describe a custom RNA packaging system from the plant virus cowpea mosaic virus to produce virus-like particles that encapsidate specifically designed portions of the genome of SARS-CoV-2, the causative agent of COVID-19. These encapsidated mimics are highly stable particles which can be used either to spike patient swab samples for use as an in-tube extraction and reaction positive control in multiplex RT-qPCR, or alone as a side-by-side mock-positive control reagent. The selection of sequences in the packaged pseudogenomes ensures that these mimics are compatible with the most commonly used primer/probe combinations for SARS-CoV-2 diagnostics (including German Berlin Charité Hospital, American CDC, and Chinese CDC protocols). The plant transient expression system used to produce these encapsidated mimics is inherently low-cost, and sufficiently high-yielding that a single laboratory-scale preparation can provide enough positive control reagent for millions of tests. ; We thank Horticultural Services at the John Innes Centre (JIC) for providing the plants necessary for this work while under the COVID-19 restrictions. At JIC this work was supported by the United Kingdom Biotechnology and Biological Sciences Research Council (BBSRC) Institute Strategic Programme Grant "Molecules from Nature – Enhanced Research Capacity" (BBS/E/J/000PR9794), and the John Innes Foundation. This work was further supported by the European Union's Horizon 2020 programme under Grant Agreements 760331 (Newcotiana) and 774078 (Pharma-Factory). Julian Ma also acknowledges generous support from the Sir Joseph Hotung Charitable Trust.
Coronaviruses (CoVs) cause severe respiratory, enteric, and systemic infections in a wide range of hosts, including humans and animals. Porcine epidemic diarrhea virus (PEDV), a member of the Coronaviridae family, is the etiological agent of porcine epidemic diarrhea (PED), a highly contagious intestinal disease affecting pigs of all ages. In this study, we optimized a viability real-time reverse transcriptase polymerase chain reaction (RT-qPCR) for the selective detection of infectious and heat-inactivated PEDV. PEMAX™, EMA™, and PMAxx™ photoactivable dyes along with PtCl4 and CDDP platinum compounds were screened as viability markers using two RT-qPCR assays: firstly, on PEDV purified RNA, and secondly on infectious and thermally inactivated virus suspensions. Furthermore, PMAxx™ pretreatment matched the thermal inactivation pattern obtained by cell culture better than other viability markers. Finally, we further optimized the pretreatment by coupling viability markers with Triton X-100 in inoculated serum resulting in a better estimation of PEDV infectivity than RT-qPCR alone. Our study has provided a rapid analytical tool based on viability RT-qPCR to infer PEDV infectivity with potential application for feed and feed ingredients monitoring in swine industry. This development would allow for greater accuracy in epidemiological surveys and outbreak investigations. ; This study was supported by the program of the National Institute of Agricultural and Food Research and Technology (INIA project E-RTA2015-0003-C02-02) of Spanish Government. HP was supported by FPU17/00466 predoctoral grant funded by Spanish Government. WR was supported by APOSTD/2018/150 postdoctoral grant funded by Generalitat Valenciana. ; Peer reviewed
Spring viremia of carp virus (SVCV) ia a carp sprivivirus and a member of the genus Sprivivirus within the family Rhabdoviridae. The virus is the etiological agent of spring viremia of carp, a disease of cyprinid species including koi Cyprinus carpio L. and notifiable to the World Organisation for Animal Health. The goal of this study was to explore hypotheses regarding intergenogroup (Ia to Id) SVCV infection dynamics in juvenile koi and contemporaneously create new reverse-transcription quantitative PCR (RT-qPCR) assays and validate their analytical sensitivity, specificity (ASp) and repeatability for diagnostic detection of SVCV. RT-qPCR diagnostic tests targeting the SVCV nucleoprotein (Q2N) or glycoprotein (Q1G) nucleotides were pan-specific for isolates typed to SVCV genogroups Ia to Id. The Q2N test had broader ASp than Q1G because Q1G did not detect SVCV isolate 20120450 and Q2N displayed occasional detection of pike fry sprivivirus isolate V76. Neither test cross-reacted with other rhabdoviruses, infectious pancreatic necrosis virus or co-localizing cyprinid herpesvirus 3. Both tests were sensitive with observed 50% limits of detection of 3 plasmid copies and high repeatability. Test analysis of koi immersed in SVCV showed that the virus could be detected for at least 167 d following exposure and that titer, prevalence, replicative rate and persistence in koi were correlated significantly with virus virulence. In this context, high virulence SVCV isolates were more prevalent, reached higher titers quicker and persisted in koi for longer periods of time relative to moderate and low virulence isolates. ; Centre of Expertise for Aquatic Animal Health Research & Development (Fisheries and Oceans Canada); Emerging Diseases Cyclical Fund (US Geological Survey) ; Published version ; This study was supported by the Centre of Expertise for Aquatic Animal Health Research & Development (Fisheries and Oceans Canada) and the Emerging Diseases Cyclical Fund (US Geological Survey). We thank Ron Hedrick and Tomo Kurobe for CyHV-3 isolate F98-50; Kyle Garver for the VHSV and IHNV isolates; and David Stone, Andrew Goodwin, Peng Jia and Hong Liu for the carp and pike fry sprivivirus isolates. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the US government.
Tomato brown rugose fruit virus (ToBRFV) represents an emerging viral threat to the productivity of tomato and pepper protected cultivation worldwide. This virus has got the status of quarantine organism in the European Union (EU) countries. In particular, tomato and pepper seeds will need to be free of ToBRFV before entering the EU and before coming on the market. Thus, lab tests are needed. Here, we develop and validate a one-step reverse transcription LAMP platform for the detection of ToBRFV in tomato and pepper leaves, by real-time assay [reverse transcription loop-mediated isothermal amplification (RT-LAMP)] and visual screening (visual RT-LAMP). Moreover, these methods can also be applied successfully for ToBRFV detection in tomato and pepper seeds. The diagnostic specificity and sensitivity of both RT-LAMP and visual RT-LAMP are both 100%, with a detection limit of nearly 2.25 fg/μl, showing the same sensitivity as RT-qPCR Sybr Green, but 100 times more sensitive than end-point RT-PCR diagnostic methods. In artificially contaminated seeds, the proposed LAMP assays detected ToBRFV in 100% of contaminated seed lots, for up to 0.025–0.033% contamination rates in tomato and pepper, respectively. Our results demonstrate that the proposed LAMP assays are simple, inexpensive, and sensitive enough for the detection of ToBRFV, especially in seed health testing. Hence, these methods have great potential application in the routine detection of ToBRFV, both in seeds and plants, reducing the risk of epidemics.
Cannabis sativa L. has been long cultivated for its narcotic potential due to the accumulation of tetrahydrocannabinolic acid (THCA) in female inflorescences, but nowadays its production for fiber, seeds, edible oil and bioactive compounds has spread throughout the world. However, some hemp varieties still accumulate traces of residual THCA close to the 0.20% limit set by European Union, despite the functional gene encoding for THCA synthase (THCAS) is lacking. Even if some hypotheses have been produced, studies are often in disagreement especially on the role of the cannabichromenic acid synthase (CBCAS). In this work a set of European Cannabis genotypes, representative of all chemotypes, were investigated from a chemical and molecular point of view. Highly specific primer pairs were developed to allow an accurate distinction of different cannabinoid synthases genes. In addition to their use as markers to detect the presence of CBCAS at genomic level, they allowed the analysis of transcriptional profiles in hemp or marijuana plants. While the high level of transcription of THCAS and cannabidiolic acid synthase (CBDAS) clearly reflects the chemical phenotype of the plants, the low but stable transcriptional level of CBCAS in all genotypes suggests that these genes are active and might contribute to the final amount of cannabinoids.
After the first COVID-19 case was reported in China in December 2019, leading to a sanitary crisis and later expanded to a pandemic, Public Health Systems were forced to adapt their facilities and capabilities to face, among other actions, the need for massive diagnostics, surveillance, monitoring immune response and assess protection post-infection and, eventually, after vaccination. In this scenario, many researchers, professionals, recent graduates and students at the School of Sciences (Facultad de Ciencias Exactas, Universidad Nacional de La Plata) assembled a multisdiciplinary team called "Grupo COVID Exactas". This group helped to set up a facility to perform routine RT-qPCR-based detection of viral RNA in clinical samples at the Laboratory of Public Health of the Secretary of Extension of the Faculty (Secretaría de Extensión de la Facultad de Ciencias Exactas de la Universidad Nacional de La Plata).To cope with the shortage of reagents worldwide and to simplify RNA isolation, a silica-coated magnetic bead-based system was developed locally to avoid centrifugation steps. At the same time, the serology group initiated specific IgG screening tests, and the research team addressed the development of immunoassays to detect SARS-CoV-2-specific IgG/IgM/IgA. Also, urine infrared and fluorescence spectra are being explored for their potential to find differential patterns associated with the disease. The seriousness of the public health problem led the signature of a cooperation agreement between the UNLP and the Ministry of Health of the Province of Buenos Aires (Ministerio de Salud de la Provincia de Buenos Aires) to update the laboratory setups, to coordinate distribution of clinical samples and laboratory and to provide with PPE supplies. It also includes the design and implementation of screening and surveillance strategies addressing issues associated with pandemics. In addition, the interest of the Government of the PBA in the specific local development of technologies and reagents at the University is the focus of another recently signed tripartite agreement that includes R&D institutes of the UNLP also associated with CONICET (Argentinean National Research Council). ; Desde que se informó el primer caso de enfermedad por COVID-19 en China, en diciembre de 2019, y se declaró la crisis sanitaria y luego la pandemia, los sistemas de Salud debieron adaptar sus estructuras para realizar diagnóstico, vigilancia, monitoreo de la respuesta inmune y evaluación de la protección inmune post-infección o post-vacunación. En este escenario el Grupo COVID Exactas, a través del Laboratorio de Salud Pública, de la Secretaría de Extensión de la Facultad de Ciencias Exactas, montó un laboratorio de diagnóstico para realizar la detección del RNA viral en muestras de pacientes mediante su amplificación RT-qPCR. Para paliar la falta de disponibilidad de reactivos y simplificar la extracción del RNA se encaró el desarrollo de un sistema basado en nanopartículas magnéticas recubiertas de sílice, que no requieren el uso de centrifuga. Al mismo tiempo, el grupo Serología comenzó a monitorear anticuerpos séricos IgG específicos, mientras que el grupo Investigación comenzó a desarrollar inmunoensayos para detección de IgG/IgM/IgA específicos y caracterización de espectros infrarrojo y fluorescente en muestras de orina. En este contexto de gravedad sanitaria la UNLP y el Ministerio de Salud de la Provincia de Buenos Aires (PBA) firmaron un convenio de cooperación y trabajaron en la adecuación de laboratorios, coordinación de distribución de muestras, provisión de reactivos e insumos y diseño de estrategias conjuntas de vigilancia para aportar soluciones al sistema de salud en el contexto de pandemia. Asimismo, el interés del Gobierno de la PBA por los desarrollos de los institutos de la UNLP y de doble dependencia UNLP-CONICET, dio lugar a otro convenio tripartito con finalidades específicas.