Quantifying Plant Viruses: Evolution from Bioassay to Infectivity Dilution Curves along the Model of Tobamoviruses.

This review describes the development of the bioassay as a means of quantifying plant viruses, with particular attention to tobamovirus. It delves into various models used to establish a correlation between virus particle concentration and the number of induced local lesions (the infectivity dilution curve), including the Poisson, Furumoto and Mickey, Kleczkowski, Growth curve, and modified Poisson models. The parameters of each model are described, and their application or performance in the context of the tobacco mosaic virus is explored. This overview highlights the enduring value of the infectivity dilution curve in tobamovirus quantification, providing valuable insights for researchers or practitioners of bioassays and theoreticians of modeling.

Implications of Below-Ground Allelopathic Interactions of Camelina sativa and Microorganisms for Phosphate Availability and Habitat Maintenance.

Toxic breakdown products of young Camelina sativa (L.) Crantz, glucosinolates can eliminate microorganisms in the soil. Since microorganisms are essential for phosphate cycling, only insensitive microorganisms with phosphate-solubilizing activity can improve C. sativa's phosphate supply. In this study, 33P-labeled phosphate, inductively coupled plasma mass spectrometry and pot experiments unveiled that not only Trichoderma viride and Pseudomonas laurentiana used as phosphate-solubilizing inoculants, but also intrinsic soil microorganisms, including Penicillium aurantiogriseum, and the assemblies of root-colonizing microorganisms solubilized as well phosphate from apatite, trigger off competitive behavior between the organisms. Driving factors in the competitiveness are plant and microbial secondary metabolites, while glucosinolates of Camelina and their breakdown products are regarded as key compounds that inhibit the pathogen P. aurantiogriseum, but also seem to impede root colonization of T. viride. On the other hand, fungal diketopiperazine combined with glucosinolates is fatal to Camelina. The results may contribute to explain the contradictory effects of phosphate-solubilizing microorganisms when used as biofertilizers. Further studies will elucidate impacts of released secondary metabolites on coexisting microorganisms and plants under different environmental conditions.

Applicability of Different Methods for Quantifying Virucidal Efficacy Using MENNO Florades and Tomato Brown Rugose Fruit Virus as an Example.

After entry of a quarantine/regulated pathogen, infected plants shall be destroyed, and the cultivated area (e.g., greenhouse) shall be disinfected. Therefore, the selection of an effective disinfectant plays an important role. With the availability of different methods for virus quantification, we investigated the application of quantitative ELISA (qELISA), RT-qPCR (reverse transcription-quantitative polymerase chain reaction), and bioassays for the quantification of disinfectant efficacy. Therefore, we estimated the titer reduction in tomato brown rugose fruit virus (ToBRFV), a regulated pathogen, in plant sap and on germ carriers after treatment with MENNO Florades 4% for 16 h. The virus load before and after the treatment was measured with the mentioned methods. The RT-qPCR and qELISA methods showed very low efficacy in the presence of the disinfectant. Although bioassays are time-consuming, need purified particles for establishing the quantification models, and are less sensitive than RT-qPCR, they were able to quantify the differences in virus titer in the presence/absence of disinfectant. Interestingly, the bioassays reached at least the lower limit sensitivity of a qELISA. By being less sensitive to the presence of the disinfectant, bioassays proved to be the only technique for the determination of the disinfectant efficacy against ToBRFV on different germ carriers as well as on virus-infected plant sap.

Comparison of Models for Quantification of Tomato Brown Rugose Fruit Virus Based on a Bioassay Using a Local Lesion Host.

Considering the availability of serological and molecular biological methods, the bioassay has been paled into insignificance, although it is the only experimental method that can be used to demonstrate the infectivity of a virus. We compared goodness-of-fit and predictability power of five models for the quantification of tomato brown rugose fruit virus (ToBRFV) based on local lesion assays: the Kleczkowski model, Furumoto and Mickey models I and II, the Gokhale and Bald model (growth curve model), and the modified Poisson model. For this purpose, mechanical inoculations onto Nicotiana tabacum L. cv. Xanthi nc and N. glutionosa L. with defined virus concentrations were first performed with half-leaf randomization in a Latin square design. Subsequently, models were implemented using Python software and fitted to the number of local lesions. All models could fit to the data for quantifying ToBRFV based on local lesions, among which the modified Poisson model had the best prediction of virus concentration in spike samples based on local lesions, although data of individual indicator plants showed variations. More accurate modeling was obtained from the test plant N. glutinosa than from N. tabacum cv. Xanthi nc. The position of the half-leaves on the test plants had no significant effect on the number of local lesions.

Hatching is modulated by microRNA-378a-3p derived from extracellular vesicles secreted by blastocysts.

SignificanceHatching from the zona pellucida is a prerequisite for embryo implantation and is less likely to occur in vitro for reasons unknown. Extracellular vesicles (EVs) are secreted by the embryo into the culture medium. Yet the role that embryonic EVs and their cargo microRNAs (miRNAs) play in blastocyst hatching has not been elucidated, partially due to the difficulties of isolating them from low amounts of culture medium. Here, we optimized EV-miRNA isolation from medium conditioned by individually cultured bovine embryos and subsequently showed that miR-378a-3p, which was up-regulated in EVs secreted by blastocysts, plays a crucial role in promoting blastocyst hatching. This demonstrates the regulatory effect of miR-378-3p on hatching, which is an established embryo quality parameter linked with implantation.

The Separation and Characterization of Extracellular Vesicles from Medium Conditioned by Bovine Embryos.

Extracellular vesicles (EVs) have been identified as one of the communication mechanisms amongst embryos. They are secreted into the embryo culture medium and, as such, represent a source of novel biomarkers for identifying the quality of cells and embryos. However, only small amounts of embryo-conditioned medium are available, which represents a challenge for EV enrichment. Our aim is to assess the suitability of different EV separation methods to retrieve EVs with high specificity and sufficient efficiency. Bovine embryo-conditioned medium was subjected to differential ultracentrifugation (DU), OptiPrepTM density gradient (ODG) centrifugation, and size exclusion chromatography. Separated EVs were characterized by complementary characterization methods, including Western blot, electron microscopy, and nanoparticle tracking analysis, to assess the efficiency and specificity. OptiPrepTM density gradient centrifugation outperformed DU and SEC in terms of specificity by substantial removal of contaminating proteins such as ribonucleoprotein complexes (Argonaute-2 (AGO-2)) and lipoproteins (ApoA-I) from bovine embryo-derived EVs (density: 1.02-1.04, 1.20-1.23 g/mL, respectively). In conclusion, ODG centrifugation is the preferred method for identifying EV-enriched components and for improving our understanding of EV function in embryo quality and development.

Characterization of the first rice paddy cluster I isolate, Methyloterricola oryzae gen. nov., sp. nov. and amended description of Methylomagnum ishizawai.

Three gammaproteobacterial methanotrophic strains (73aT, 175 and 114) were isolated from stems of rice plants. All strains are Gram-negative, motile and grow on methane or methanol as sole carbon sources. They oxidize methane using the particulate methane monooxygenase. Strains 114 and 175 possess additionally a soluble methane monooxygenase. All strains contain significant amounts of the cellular fatty acids C16 : 0, C16 : 1ω6c and C16 : 1ω7c, typical for type Ib methanotrophs. Characteristic for strains 114 and 175 are high amounts of C14 : 0 and C16 : 1ω6c , while strain 73aT contains high quantities of C16 : 1ω5c. 16S rRNA gene sequence analyses showed that strains 114 and 175 are most closely related to Methylomagnum ishizawai (≥99.6 % sequence identity). Strain 73aT is representing a new genus within the family Methylococcaceae, most closely related to Methylococcus capsulatus (94.3 % sequence identity). Phylogenetic analysis of the PmoA sequence indicates that strain 73aT represents rice paddy cluster I (RPCI), which has almost exclusively been detected in rice ecosystems. The G+C content of strain 73aT is 61.0 mol%, while strains 114 and 175 have a G+C content of 63.3 mol%. Strain 73aT (=LMG 29185T, =VKM B-2986T) represents the type strain of a novel species and genus, for which the name Methyloterricola oryzae gen. nov., sp. nov. is proposed and a description is provided. Strains 175 (=LMG 28717, VKM B-2989) and 114 are members of the species Methylomagnum ishizawai. This genus was so far only represented by one isolate, so an amended description of the species is given.

Application of surface plasmon resonance imaging technique for the detection of single spherical biological submicrometer particles.

Recent proof-of-principle studies demonstrated the suitability of the surface plasmon resonance imaging (SPRi) technique for the detection of individual submicrometer and nanoparticles in solutions. In the current study, we used the SPRi technique for visualization of the binding of round-shaped viruses (inactivated influenza A virus) and virus-like particles (human immunodeficiency virus (HIV)-based virus-like particles) to the functionalized sensor surface. We show the applicability of the SPRi technique for the detection of individual virus-like particles in buffers without serum as well as in buffers containing different concentrations of serum. Furthermore, we prove the specificity of visualized binding events using two different pseudotypes of HIV virus-like particles. We also demonstrate the applicability of the SPRi technique for the determination of relative particle concentrations in solutions. Moreover, we suggest a technical approach, which allows enhancing the magnitude of binding signals. Our studies indicate that the SPRi technique represents an efficient research tool for quantification and characterization of biological submicrometer objects such as viruses or virus-like particles, for example.