A novel botybirnavirus with a unique satellite dsRNA causes latent infection in Didymella theifolia isolated from tea plants

© 2023 The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/The unique, recently discovered fungus Didymella theifolia specifically infects local varieties of tea plant Camellia sinensis in China, and therefore, the characterization of its mycoviruses is important. Three double-stranded (ds) RNAs (1, 2, and 3, with 6,338, 5,910, and 727 bp in size, respectively) were identified in the avirulent D. theifolia strain CJP4-1, which exhibits normal growth and morphology. Characterization of these double-stranded RNAs (dsRNAs) revealed that the two largest elements are the genomic components of a novel botybirnavirus, tentatively named Didymella theifolia botybirnavirus 1 (DtBRV1). Conversely, dsRNA3 shares no detectable similarity with sequences deposited in public databases but has high similarity with the 5′-terminal regions of dsRNAs 1 and 2 and contains a duplicated region encoding a putative small peptide. All three dsRNAs are encapsidated in isometric virions ca. 40 nm in diameter, supporting the notion that dsRNA3 is a DtBRV1 satellite. SDS-polyacrylamide gel electrophoresis in combination with peptide mass fingerprint analysis revealed that the DtBRV1 capsid protein consists of polypeptides encoded by the 5′-terminal regions of both genomic components dsRNA1 and dsRNA2. Vertical transmission of DtBRV1 through conidia is efficient, while its horizontal transmission from CJP4-1 to other strains was not detected. DtBRV1, with or without dsRNA3, has no obvious effects on fungal growth and virulence, as illustrated following transfection of the virulent D. theifolia strain JYC1-6. In summary, DtBRV1 exhibits unique molecular traits and contributes to our understanding of mycovirus diversity.Peer reviewe

Route to, and control of chaos in multidimensional systems

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references (leaves 61-62).Issued also on microfiche from Lange Micrographics.The goal of this thesis is to analyze the dynamic behavior of a given nonlinear system and then control the chaotic behavior of the system within some ranges of the parameters. In the first part of this thesis, we study the effect of a harmonic forcing function and the strength of the nonlinearity on a specific two-degree of freedom system namely, an elastic pendulum, with internal resonance. The forcing function amplitude is used here as the control parameter and the system's dynamics are studied through the variation of this parameter. It was found that the route to chaos always begins, in the pendulum system, with a secondary Hopf Bifurcation followed by consecutive torus doubling bifurcations, ending with torus breaking. A comparison is also made between the use of a linear spring, a weakly nonlinear spring and a strongly nonlinear spring. We observed that the nonlinearity could aid in the stabilization of the periodic orbit beyond the previously seen threshold of instability. Yet, if the strength of the nonlinearity is sufficiently large, it can lead to chaos in frequency regimes where chaos previously was not observed. The second part of this thesis is meant as both a comparison and description of the various methods currently used to control chaos, with application to a rotor supported on nonlinear ball bearings. There are two main types of control schemes. The first is the OGY method and the second is the periodic perturbation method. Both methods depend on the fact that when dealing with chaos small perturbations applied to a parameter of the system can affect the dynamics drastically. The periodic perturbations method is an open loop non-feedback method while the OGY is a closed loop method that depends largely on feedback to achieve the desired effect. We attempted in this thesis to distinguish the conditions for the success and failure of each method. It was found that the OGY method consumes the least energy in its application, and is most suitable when there is only one unstable manifold found for the saddle orbit. It was also found that from an application point of view, the periodic perturbation method is much simpler and can be applied on-line (in real time), no matter how many unstable manifolds the system has

Genomic analysis of Colletotrichum camelliae responsible for tea brown blight disease

Abstract Background Colletotrichum camelliae, one of the most important phytopathogenic fungi infecting tea plants (Camellia sinensis), causes brown blight disease resulting in significant economic losses in yield of some sensitive cultivated tea varieties. To better understand its phytopathogenic mechanism, the genetic information is worth being resolved. Results Here, a high-quality genomic sequence of C. camelliae (strain LT-3-1) was sequenced using PacBio RSII sequencing platform, one of the most advanced Three-generation sequencing platforms and assembled. The result showed that the fungal genomic sequence is 67.74 Mb in size (with the N50 contig 5.6 Mb in size) containing 14,849 putative genes, of which about 95.27% were annotated. The data revealed a large class of genomic clusters potentially related to fungal pathogenicity. Based on the Pathogen Host Interactions database, a total of 1698 genes (11.44% of the total ones) were annotated, containing 541 genes related to plant cell wall hydrolases which is remarkably higher than those of most species of Colletotrichum and others considered to be hemibiotrophic and necrotrophic fungi. It’s likely that the increase in cell wall-degrading enzymes reflects a crucial adaptive characteristic for infecting tea plants. Conclusion Considering that C. camelliae has a specific host range and unique morphological and biological traits that distinguish it from other species of the genus Colletotrichum, characterization of the fungal genome will improve our understanding of the fungus and its phytopathogenic mechanism as well

Amplicon Sequencing Reveals Novel Fungal Species Responsible for a Controversial Tea Disease

Amplicon sequencing is a powerful tool for analyzing the fungal composition inside plants, whereas its application for the identification of etiology for plant diseases remains undetermined. Here, we utilize this strategy to clarify the etiology responsible for tea leaf brown-black spot disease (LBSD), a noticeable disease infecting tea plants etiology that remains controversial. Based on the ITS-based amplicon sequencing analysis, Didymella species were identified as separate from Pestalotiopsis spp. and Cercospora sp., which are concluded as the etiological agents. This was further confirmed by the fungal isolation and their specific pathogenicity on diverse tea varieties. Based on the morphologies and phylogenetic analysis constructed with multi-loci (ITS, LSU, tub2, and rpb2), two novel Didymella species—tentatively named D. theae and D. theifolia as reference to their host plants—were proposed and characterized. Here, we present an integrated approach of ITS-based amplicon sequencing in combination with fungal isolation and fulfillment of Koch’s postulates for etiological identification of tea plant disease, revealing new etiology for LBSD. This contributes useful information for further etiological identification of plant disease based on amplicon sequencing, as well as understanding, prevention, and management of this economically important disease

A circular single-stranded DNA mycovirus infects plants and confers broad-spectrum fungal resistance

© 2024 The Author(s). Published by the Molecular Plant Shanghai Editorial Office in association with Cell Press, an imprint of Elsevier Inc., on behalf of CSPB and CEMPS, CAS. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/Circular single-stranded DNA (ssDNA) viruses have been rarely found in fungi, and the evolutionary and ecological relationships among ssDNA viruses infecting fungi and other organisms remain unclear. In this study, a novel circular ssDNA virus, tentatively named Diaporthe sojae circular DNA virus 1 (DsCDV1), was identified in the phytopathogenic fungus Diaporthe sojae isolated from pear trees. DsCDV1 has a monopartite genome (3185 nt in size) encapsidated in isometric virions (21?26 nm in diameter). The genome comprises seven putative open reading frames encoding a discrete replicase (Rep) split by an intergenic region, a putative capsid protein (CP), several proteins of unknown function (P1?P4), and a long intergenic region. Notably, the two split parts of DsCDV1 Rep share high identities with the Reps of Geminiviridae and Genomoviridae, respectively, indicating an evolutionary linkage with both families. Phylogenetic analysis based on Rep or CP sequences placed DsCDV1 in a unique cluster, supporting the establishment of a new family, tentatively named Gegemycoviridae, intermediate to both families. DsCDV1 significantly attenuates fungal growth and nearly erases fungal virulence when transfected into the host fungus. Remarkably, DsCDV1 can systematically infect tobacco and pear seedlings, providing broad-spectrum resistance to fungal diseases. Subcellular localization analysis revealed that DsCDV1 P3 is systematically localized in the plasmodesmata, while its expression in trans-complementation experiments could restore systematic infection of a movement-deficient plant virus, suggesting that P3 is a movement protein. DsCDV1 exhibits unique molecular and biological traits not observed in other ssDNA viruses, serving as a link between fungal and plant ssDNA viruses and presenting an evolutionary connection between ssDNA viruses and fungi. These findings contribute to expanding our understanding of ssDNA virus diversity and evolution, offering potential biocontrol applications for managing crucial plant diseases.Peer reviewe

SARS-CoV-2 precipitating a stroke in a child? A case report from Tanzani

There is scanty data on overall pediatric presentations with COVID-19 in sub-Saharan Africa and none reported related to stroke. Management of acute stroke in children has been challenging due to delays in presentation and difficulties in deducing the exact etiology. This is the first such case of a stroke in a child with COVID-19 infection reported in Tanzania to the best of our knowledge. A six-and-a-half-year-old male child of Asian origin with no history of chronic illness presented to our facility with fever, rash, gastrointestinal symptoms and conjunctivitis. Subsequently, he developed headache, irritability, altered mentation, loss of speech, facial nerve palsy and hemiparesis. He was provisionally diagnosed with bacterial meningitis with a differential diagnosis of viral encephalitis and received standard treatment for the same. On further investigations, magnetic resonance imaging (MRI) of the brain showed ischemic infarct along the territory of left middle cerebral artery and given the history of the child´s exposure to a relative with COVID-19 infection, child underwent a nasopharyngeal swab for polymerase chain reaction testing which was negative but the serum IgG for COVID was positive. Despite the severe presentation initially, early detection and appropriate management resulted in survival, regained speech and motor function. Due to constraints in health care systems in sub-Saharan Africa, it is difficult to exhaust the diagnostics in order to narrow down the list of differentials in a child with stroke. This case is reported to further describe the diverse presentations of COVID-19 particularly in children which has been under-represented especially in sub-Saharan Africa. Attending physicians should have a high index of suspicion for SARS-CoV-2 as the etiology for exposed children presenting with neurological symptoms

Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries

Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally. Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression. Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed. Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas

Determinants of morbidity and mortality following emergency abdominal surgery in children in lowincome and middle-income countries

Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resourcepoor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally. Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression. Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed. Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas