Publications by authors named "Tim Sit"

Article Synopsis
  • D'Ann Rochon, who passed away on November 29, 2022, made significant contributions to plant virology and was dedicated to mentoring young scientists.
  • She worked as a research scientist for Agriculture and Agri-Food Canada and served as an Adjunct Professor at the University of British Columbia.
  • Her research advanced the understanding of tombusviruses, including innovations in virus structure, transmission by fungal zoospores, and plant-virus interactions, as well as developing important diagnostic antibodies for plum pox virus and little cherry virus 2.
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Sustainable practices that reduce food loss are essential for enhancing global food security. We report a 'wrap and plant' seed treatment platform to protect crops from soil-borne pathogens. Developed from the abundantly available wastes of banana harvest and recycled old, corrugated cardboard boxes via chemical-free pulping, these paper-like biodegradable seed wraps exhibit tunable integrity and bioavailability of loaded moieties.

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Take-all root rot is a disease of ultradwarf bermudagrass putting greens caused by (Gg), sp. (Gx), (Ggram), (Cc), and (Mc). Many etiological and epidemiological components of this disease remain unknown.

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Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread natural and anthropogenic pollutants, and some PAHs are proven developmental toxicants. We chemically characterized clean and heavily polluted sites and exposed fish embryos to PAH polluted sediment extracts during four critical developmental stages. Embryos were collected from Fundulus heteroclitus populations inhabiting the clean and heavily polluted Superfund estuary.

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Background: The Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 system has become a powerful tool for functional genomics in plants. The RNA-guided nuclease can be used to not only generate precise genomic mutations, but also to manipulate gene expression when present as a deactivated protein (dCas9).

Results: In this study, we describe a vector toolkit for analyzing dCas9-mediated activation (CRISPRa) or inactivation (CRISPRi) of gene expression in maize protoplasts.

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Climate changes, emerging species of plant pests, and deficits of clean water and arable land have made availability of food to the ever-increasing global population a challenge. Excessive use of synthetic pesticides to meet ever-increasing production needs has resulted in development of resistance in pest populations, as well as significant ecotoxicity, which has directly and indirectly impacted all life-forms on earth. To meet the goal of providing safe, sufficient, and high-quality food globally with minimal environmental impact, one strategy is to focus on targeted delivery of pesticides using eco-friendly and biodegradable carriers that are derived from naturally available materials.

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Controlled release and targeted delivery of agrochemicals are crucial for achieving effective crop protection with minimal damage to the environment. This work presents an innovative and cost-effective approach to fabricate lignocellulose-based biodegradable porous matrices capable of slow and sustained release of the loaded molecules for effective crop protection. The matrix exhibits tunable physicochemical properties which, when coupled with our unique "wrap-and-plant" concept, help to utilize it as a defense against soil-borne pests while providing controlled release of crop protection moieties.

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Article Synopsis
  • Plant viruses, like Tomato spotted wilt virus (TSWV), depend on insect vectors such as Thrips tabaci for spreading among plants, yet the specifics of their interactions remain unclear.
  • Different isolates of TSWV show varied transmission rates depending on the T. tabaci population, suggesting a complex relationship between them.
  • This study found that local pairings of TSWV isolates and T. tabaci had higher transmission rates, but surprisingly showed lower virus levels in the thrips, indicating that both specific interactions and adaptation play crucial roles in how effectively TSWV is transmitted.
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Nematode-infecting RNA viruses have recently been discovered via transcriptome sequencing. In soybean cyst nematode (SCN; Heterodera glycines), seven single-stranded RNA viruses have been identified from transcriptome data and experimentally confirmed with qRT-PCR and Sanger sequencing. Presently, there is still much unknown about the relationship between these viruses and the nematode host.

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Article Synopsis
  • A new fluorescence hybridization (FISH) protocol was created for nematodes that uses electroporation to introduce nucleic acid probes directly into the organism.
  • This streamlined method reduces chemical wash steps, leading to lower specimen loss and faster protocol times, specifically optimized for juveniles of soybean cyst nematodes.
  • The protocol allows for the simultaneous detection of two different targets using long wavelength fluorophores, which enhances hybridization sensitivity and may be adapted for other nematode species and life stages.
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Members of the family have highly similar structures, and yet there are important differences among them in host, transmission, and capsid stabilities. Viruses in the family have single-stranded RNA (ssRNA) genomes with T=3 icosahedral protein shells with a maximum diameter of ∼340 Å. Each capsid protein is comprised of three domains: R (RNA binding), S (shell), and P (protruding).

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Tobacco mosaic virus (TMV) is an extensively studied RNA virus known to infect tobacco () and other solanaceous crops. TMV has been classified as a seedborne virus in tobacco, with infection of developing seedlings thought to occur from contact with the TMV-infected seed coat. The mechanism of TMV transmission through seed was studied in seed of the K 326 cultivar of flue-cured tobacco.

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Nanoparticle formulations of agrichemicals may enhance their performance while simultaneously mitigating any adverse environmental effects. Red clover necrotic mosaic virus (RCNMV) is a soil-transmitted plant virus with many inherent attributes that allow it to function as a plant virus-based nanoparticle (PVN) when loaded with biologically active ingredients. Here we describe how to formulate a PVN loaded with the nematicide abamectin (Abm) beginning with the propagation of the virus through the formulation, deactivation, and characterization of the finished product.

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Folded RNA elements that block processive 5' → 3' cellular exoribonucleases (xrRNAs) to produce biologically active viral noncoding RNAs have been discovered in flaviviruses, potentially revealing a new mode of RNA maturation. However, whether this RNA structure-dependent mechanism exists elsewhere and, if so, whether a singular RNA fold is required, have been unclear. Here we demonstrate the existence of authentic RNA structure-dependent xrRNAs in dianthoviruses, plant-infecting viruses unrelated to animal-infecting flaviviruses.

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Drosophila suzukii Matsumura (Diptera: Drosophilidae) is an invasive, highly polyphagous pest of soft-skinned fruits throughout much of the world. A better understanding of the ecology of adult flies, including their nutritional resources, is needed to advance ecologically based management approaches. In this study, we evaluate the capability of polymerase chain reaction-based gut content analysis to detect a known food resource from DNA extracted from laboratory-reared flies.

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Article Synopsis
  • The study explores the emerging field of invertebrate virology, focusing on five confirmed RNA viruses in the soybean cyst nematode (SCN), which are widespread in field and greenhouse populations.
  • Two new viruses, SCN nyami-like virus (NLV) and SCN bunya-like virus (BLV), were identified through transcriptome sequencing of SCN populations, while a potential third virus, PCN picorna-like virus (PLV), was discovered in potato cyst nematodes using publicly available data.
  • The presence of these viruses was confirmed using various molecular techniques, highlighting their potential impact on nematode ecology and management strategies, although further research is needed to understand their biological and evolutionary roles.
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Article Synopsis
  • Five viruses infecting soybean cyst nematodes (SCN) were found in populations from Illinois, North Carolina, and Missouri, with global analysis using qRT-PCR.
  • Viral levels in greenhouse cultures stayed consistent throughout the SCN's development stages, indicating ongoing viral replication, while lower levels were detected in field populations.
  • There were variances in the presence of viruses across different cultures, and some nematode species were also found to harbor these viruses, suggesting they could affect nematode behavior and control strategies.
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Plant parasitic nematodes are one of the world's major agricultural pests, causing in excess of $157 billion in worldwide crop damage annually. Abamectin (Abm) is a biological pesticide with a strong activity against a wide variety of plant parasitic nematodes. However, Abm's poor mobility in the soil compromises its nematicide performance because of the limited zone of protection surrounding the growing root system of the plant.

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Loading and release mechanisms of Red clover necrotic mosaicvirus (RCNMV) derived plant viral nanoparticle (PVN) are shown for controlled delivery of the anticancer drug, doxorubicin (Dox). Previous studies demonstrate that RCNMV's structure and unique response to divalent cation depletion and re-addition enables Dox infusion to the viral capsid through a pore formation mechanism. However, by controlling the net charge of RCNMV outer surface and accessibility of RCNMV interior cavity, tunable release of PVN is possible via manipulation of the Dox loading capacity and binding locations (external surface-binding or internal capsid-encapsulation) with the RCNMV capsid.

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Article Synopsis
  • Adaptations to polluted environments, like those seen in Fundulus heteroclitus embryos, illustrate significant phenotypic changes due to gene expression and regulation during critical developmental stages.
  • While embryos from a non-polluted population fail to survive exposure to contaminated sediment, embryos from a polluted environment show a remarkable resistance.
  • The study found that although resistant embryos largely remain unaffected by harmful PAHs, only a small percentage of genes exhibited differences in expression, challenging the assumption that dramatic morphological differences correlate with varying gene expression levels.
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The red clover necrotic mosaic virus (RCNMV) bipartite RNA genome is packaged into two virion populations containing either RNA-1 and RNA-2 or multiple copies of RNA-2 only. To understand this distinctive packaging scheme, we investigated the RNA-binding properties of the RCNMV capsid protein (CP). Maltose binding protein-CP fusions exhibited the highest binding affinities for RNA probes containing the RNA-2 trans-activator or the 3' non-coding region from RNA-1.

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Red clover necrotic mosaic virus (RCNMV) is a 36-nm-diameter, T = 3 icosahedral plant virus with a genome that is split between two single-stranded RNA molecules of approximately 3.9 kb and 1.5 kb, as well as a 400-nucleotide degradation product.

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The interaction between viral capsid protein (CP) and its cognate viral RNA modulates many steps in the virus infection cycle, such as replication, translation and assembly. The N-terminal 50 amino acids of the Red clover necrotic mosaic virus (RCNMV) CP are rich in basic residues (especially lysine) and are essential for the core functions of the CP, namely RNA binding and virion assembly. To further elucidate additional biological roles for these basic residues, a series of alanine substitution mutations was introduced into infectious clones of RCNMV RNA-1 and assayed for symptomatology, virion formation and systemic infection.

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Background: Describing the patterns of gene expression during embryonic development has broadened our understanding of the processes and patterns that define morphogenesis. Yet gene expression patterns have not been described throughout vertebrate embryogenesis. This study presents statistical analyses of gene expression during all 40 developmental stages in the teleost Fundulus heteroclitus using four biological replicates per stage.

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Red clover necrotic mosaic virus (RCNMV) is a species that belongs to the Tombusviridae family of plant viruses with a T = 3 icosahedral capsid. RCNMV virions were purified and were crystallized for X-ray analysis using the hanging-drop vapor-diffusion method. Self-rotation functions and systematic absences identified the space group as I23, with two virions in the unit cell.

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