scholarly journals Potyviral 6K2 Protein Long-Distance Movement and Symptom-Induction Functions Are Independent and Host-Specific

2004 ◽  
Vol 17 (5) ◽  
pp. 502-510 ◽  
Author(s):  
Carl Spetz ◽  
Jari P. T. Valkonen
Keyword(s):  
Spontaneous Mutation ◽  
Systemic Infection ◽  
Wild Type ◽  
Virus Propagation ◽  
Long Distance ◽  
Potato Virus A ◽  
Viral Mutant ◽  
Membrane Bound ◽  
Long Distance Movement

Deletion of various portions, or insertion of six histidine residues (6×His) into various positions of the membrane-bound 6K2 protein (53 amino acids) of Potato virus A (PVA, genus Potyvirus), inhibited systemic infection in Nicotiana tabacum and N. benthamiana plants. However, a spontaneous mutation (Gly2Cys) that occurred in 6K2 adjacent to the 6×His insert placed between Ser1 and Gly2 enabled systemic infection in a single N. benthamiana plant. No symptoms were observed, but virus titers were similar to the symptom-inducing wild-type (wt) PVA. N. tabacum plants were not systemically infected, albeit virus propagation was observed in inoculated protoplasts. The 6×His/Gly2Cys mutant was reconstructed in vitro and serially propagated by mechanical inoculation in N. benthamiana. Following the third passage, a novel viral mutant appeared, lacking the last four His residues of the insert, as well as the Gly2 and Thr3 of 6K2. It infected N. tabacum plants systemically, and in the systemically infected N. benthamiana leaves, vein chlorosis and mild yellowing symptoms were observed, typical of wt PVA infection. The mutant virus accumulated to titers similar to wt PVA in both hosts. These results show that the PVA 6K2 protein affects viral long-distance movement and symptom induction independently and in a host-specific manner.

scholarly journals Maize resistance to Sugarcane mosaic virus

2017 ◽  
Vol 38 (SI 2 - 6th Conf EFPP 2002) ◽  
pp. 542-544
Author(s):  
R. Pokorný ◽  
M. Porubová
Keyword(s):  
Mosaic Virus ◽  
Systemic Infection ◽  
Sugarcane Mosaic Virus ◽  
Resistant Line ◽  
Mechanisms Of Resistance ◽  
Long Distance ◽  
Maize Hybrids ◽  
Resistant Lines ◽  
Maize Resistance ◽  
Long Distance Movement

Under greenhouse conditions 12 maize hybrids derived from crosses of four resistant lines with several lines of different level of susceptibility were evaluated for resistance to Czech isolate of Sugarcane mosaic virus (SCMV). These hybrids were not fully resistant to isolate of SCMV, but the symptoms on their newly growing leaves usually developed 1 to 3 weeks later in comparison with particular susceptible line, the course of infection was significantly slower and rate of infection lower. As for mechanisms of resistance, the presence of SCMV was detected by ELISA in inoculated leaves both of resistant and susceptible lines, but virus was detected 7 days later in resistant line. Systemic infection developed only in susceptible lines. These results indicate restriction of viral long distance movement in the resistant line.

scholarly journals Beet necrotic yellow vein virus subgenomic RNA3 is a cleavage product leading to stable non-coding RNA required for long-distance movement

2012 ◽  
Vol 93 (5) ◽  
pp. 1093-1102 ◽  
Author(s):  
Claire Peltier ◽  
Elodie Klein ◽  
Kamal Hleibieh ◽  
Massimiliano D’Alonzo ◽  
Philippe Hammann ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Rna Virus ◽  
Cleavage Product ◽  
Yellow Vein ◽  
35S Promoter ◽  
Long Distance ◽  
Non Coding Rna ◽  
Long Distance Movement

Beet necrotic yellow vein virus (BNYVV) is a multipartite RNA virus. BNYVV RNA3 does not accumulate in non-host transgenic Arabidopsis thaliana plants when expressed using a 35S promoter. However, a 3′-derivative species has been detected in transgenic plants and in transient expression assays conducted in Nicotiana benthamiana and Beta macrocarpa. The 3′-derivative species is similar to the previously reported subgenomic RNA3 produced during virus infection. 5′ RACE revealed that the truncated forms had identical 5′ ends. The 5′ termini carried the coremin motif also present on BNYVV RNA5, beet soil-borne mosaic virus RNA3 and 4, and cucumber mosaic virus group 2 RNAs. This RNA3 species lacks a m7Gppp at the 5′ end of the cleavage products, whether expressed transiently or virally. Mutagenesis revealed the importance of the coremin sequence for both long-distance movement and stabilization of the cleavage product in vivo and in vitro. The isolation of various RNA3 5′-end products suggests the existence of a cleavage between nt 212 and 1234 and subsequent exonucleolytic degradation, leading to the accumulation of a non-coding RNA. When RNA3 was incubated in wheatgerm extracts, truncated forms appeared rapidly and their appearance was protein- and divalent ion-dependent.

scholarly journals The Rate of Cell-to-Cell Movement in Squash of Cucumber Mosaic Virus Is Affected by Sequences of the Capsid Protein

1999 ◽  
Vol 12 (7) ◽  
pp. 628-632 ◽  
Author(s):  
Sek-Man Wong ◽  
Sharon Swee-Chin Thio ◽  
Michael H. Shintaku ◽  
Peter Palukaitis
Keyword(s):  
Amino Acids ◽  
Cucumber Mosaic Virus ◽  
Mosaic Virus ◽  
Capsid Protein ◽  
Cell Movement ◽  
Systemic Infection ◽  
Long Distance ◽  
Local Movement ◽  
Long Distance Movement

The M strain of cucumber mosaic virus (CMV) does not infect squash plants systemically and moves very slowly in inoculated cotyledons. Systemic infection and an increase in the rate of local movement were observed when amino acids 129 or 214 of the M-CMV capsid protein (CP) were altered to those present in the Fny strain of CMV. While the opposite alterations to the CP of Fny-CMV inhibited systemic infection of squash, they did not show the same effects on the rates of both cell-to-cell and long-distance movement. However, the ability of CMV to infect squash systemically was affected by the rate of cell-to-cell movement.

scholarly journals Salmonella enterica Serovar Enteritidis Pathogenicity Island 1 Is Not Essential for but Facilitates Rapid Systemic Spread in Chickens

2009 ◽  
Vol 77 (7) ◽  
pp. 2866-2875 ◽  
Author(s):  
Taseen S. Desin ◽  
Po-King S. Lam ◽  
Birgit Koch ◽  
Claudia Mickael ◽  
Emil Berberov ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Systemic Infection ◽  
Poultry Meat ◽  
Wild Type ◽  
Secretion Systems ◽  
Salmonella Enterica Serovar Enteritidis ◽  
Systemic Spread ◽  
Mutant Strains ◽  
Vitro Analysis

ABSTRACT Salmonella enterica subsp. enterica serovar Enteritidis is a leading cause of human food-borne illness that is mainly associated with the consumption of contaminated poultry meat and eggs. To cause infection, S. Enteritidis is known to use two type III secretion systems, which are encoded on two salmonella pathogenicity islands, SPI-1 and SPI-2, the first of which is thought to play a major role in invasion and bacterial uptake. In order to study the role of SPI-1 in the colonization of chicken, we constructed deletion mutants affecting the complete SPI-1 region (40 kb) and the invG gene. Both ΔSPI-1 and ΔinvG mutant strains were impaired in the secretion of SipD, a SPI-1 effector protein. In vitro analysis using polarized human intestinal epithelial cells (Caco-2) revealed that both mutant strains were less invasive than the wild-type strain. A similar observation was made when chicken cecal and small intestinal explants were coinfected with the wild-type and ΔSPI-1 mutant strains. Oral challenge of 1-week-old chicken with the wild-type or ΔSPI-1 strains demonstrated that there was no difference in chicken cecal colonization. However, systemic infection of the liver and spleen was delayed in birds that were challenged with the ΔSPI-1 strain. These data demonstrate that SPI-1 facilitates systemic infection but is not essential for invasion and systemic spread of the organism in chickens.

scholarly journals Single passage in mouse organs enhances the survival and spread of Salmonella enterica

2015 ◽  
Vol 12 (113) ◽  
pp. 20150702 ◽  
Author(s):  
Richard Dybowski ◽  
Olivier Restif ◽  
Alexandre Goupy ◽  
Duncan J. Maskell ◽  
Piero Mastroeni ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Probability Generating Function ◽  
Systemic Infection ◽  
Original Method ◽  
Wild Type ◽  
Immigration Process ◽  
Serovar Typhimurium ◽  
Intravenous Inoculation

Intravenous inoculation of Salmonella enterica serovar Typhimurium into mice is a prime experimental model of invasive salmonellosis. The use of wild-type isogenic tagged strains (WITS) in this system has revealed that bacteria undergo independent bottlenecks in the liver and spleen before establishing a systemic infection. We recently showed that those bacteria that survived the bottleneck exhibited enhanced growth when transferred to naive mice. In this study, we set out to disentangle the components of this in vivo adaptation by inoculating mice with WITS grown either in vitro or in vivo . We developed an original method to estimate the replication and killing rates of bacteria from experimental data, which involved solving the probability-generating function of a non-homogeneous birth–death–immigration process. This revealed a low initial mortality in bacteria obtained from a donor animal. Next, an analysis of WITS distributions in the livers and spleens of recipient animals indicated that in vivo -passaged bacteria started spreading between organs earlier than in vitro -grown bacteria. These results further our understanding of the influence of passage in a host on the fitness and virulence of Salmonella enterica and represent an advance in the power of investigation on the patterns and mechanisms of host–pathogen interactions.

scholarly journals Morphogenic Effects of Ezrin Require a Phosphorylation-Induced Transition from Oligomers to Monomers at the Plasma Membrane

2000 ◽  
Vol 150 (1) ◽  
pp. 193-204 ◽  
Author(s):  
Alexis Gautreau ◽  
Daniel Louvard ◽  
Monique Arpin
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cells ◽  
Wild Type ◽  
Erm Proteins ◽  
Threonine Residue ◽  
Phosphorylation Event ◽  
Membrane Bound

ERM (ezrin, radixin, moesin) proteins act as linkers between the plasma membrane and the actin cytoskeleton. An interaction between their NH2- and COOH-terminal domains occurs intramolecularly in closed monomers and intermolecularly in head-to-tail oligomers. In vitro, phosphorylation of a conserved threonine residue (T567 in ezrin) in the COOH-terminal domain of ERM proteins disrupts this interaction. Here, we have analyzed the role of this phosphorylation event in vivo, by deriving stable clones producing wild-type, T567A, and T567D ezrin from LLC-PK1 epithelial cells. We found that T567A ezrin was poorly associated with the cytoskeleton, but was able to form oligomers. In contrast, T567D ezrin was associated with the cytoskeleton, but its distribution was shifted from oligomers to monomers at the membrane. Moreover, production of T567D ezrin induced the formation of lamellipodia, membrane ruffles, and tufts of microvilli. Both T567A and T567D ezrin affected the development of multicellular epithelial structures. Collectively, these results suggest that phosphorylation of ERM proteins on this conserved threonine regulates the transition from membrane-bound oligomers to active monomers, which induce and are part of actin-rich membrane projections.

scholarly journals Components of Arabidopsis Defense- and Ethylene-Signaling Pathways Regulate Susceptibility to Cauliflower mosaic virus by Restricting Long-Distance Movement

2007 ◽  
Vol 20 (6) ◽  
pp. 659-670 ◽  
Author(s):  
Andrew J. Love ◽  
Valérie Laval ◽  
Chiara Geri ◽  
Janet Laird ◽  
A. Deri Tomos ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Systemic Acquired Resistance ◽  
Fluorescent Protein ◽  
Acquired Resistance ◽  
Systemic Infection ◽  
Cauliflower Mosaic Virus ◽  
Virus Movement ◽  
Wild Type ◽  
Long Distance ◽  
Systemic Spread

We analyzed the susceptibility of Arabidopsis mutants with defects in salicylic acid (SA) and jasmonic acid (JA)/ethylene (ET) signaling to infection by Cauliflower mosaic virus (CaMV). Mutants cpr1-1 and cpr5-2, in which SA-dependent defense signaling is activated constitutively, were substantially more resistant than the wild type to systemic infection, implicating SA signaling in defense against CaMV. However, SA-deficient NahG, sid2-2, eds5-1, and pad4-1 did not show enhanced susceptibility. A cpr5 eds5 double mutant also was resistant, suggesting that resistance in cpr5 may function partially independently of SA. Treatment of cpr5 and cpr5 eds5, but not cpr1, with salicyl-hydroxamic acid, an inhibitor of alternative oxidase, partially restored susceptibility to wild-type levels. Mutants etr1-1, etr1-3, and ein2-1, and two mutants with lesions in ET/JA-mediated defense, eds4 and eds8, also showed reduced virus susceptibility, demonstrating that ET-dependent responses also play a role in susceptibility. We used a green fluorescent protein (GFP)-expressing CaMV recombinant to monitor virus movement. In mutants with reduced susceptibility, cpr1-1, cpr5-2, and etr1-1, CaMV-GFP formed local lesions similar to the wild type, but systemic spread was almost completely absent in cpr1 and cpr5 and was substantially reduced in etr1-1. Thus, mutations with enhanced systemic acquired resistance or compromised ET signaling show diminished long-distance virus movement.

scholarly journals Epstein-Barr Virus BNRF1 Protein Allows Efficient Transfer from the Endosomal Compartment to the Nucleus of Primary B Lymphocytes

2006 ◽  
Vol 80 (19) ◽  
pp. 9435-9443 ◽  
Author(s):  
R. Feederle ◽  
B. Neuhierl ◽  
G. Baldwin ◽  
H. Bannert ◽  
B. Hub ◽  
...  
Keyword(s):  
B Cells ◽  
Epstein Barr Virus ◽  
Wild Type ◽  
Barr Virus ◽  
Fold Reduction ◽  
Viral Particles ◽  
Viral Mutant ◽  
Tumor Virus ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) is a tumor virus with marked B lymphotropism. After crossing the B-cell membrane, the virus enters cytoplasmic vesicles, where decapsidation takes place to allow transfer of the viral DNA to the cell nucleus. BNRF1 has been characterized as the EBV major tegument protein, but its precise function is unknown. We have constructed a viral mutant that lacks the BNRF1 gene and report here its in vitro phenotype. A recombinant virus devoid of BNRF1 (ΔBNRF1) showed efficient DNA replication and production of mature viral particles. B cells infected with the ΔBNRF1 mutant presented viral lytic antigens as efficiently as B cells infected with wild-type or BNRF1 trans-complemented ΔBNRF1 viruses. Antigen presentation in B cells infected with either wild-type (EBV-wt) or ΔBNRF1 virus was blocked by leupeptin addition, showing that both viruses reach the endosome/lysosome compartment. These data were confirmed by direct observation of the mutant virus in endosomes of infected B cells by electron microscopy. However, we observed a 20-fold reduction in the number of B cells expressing the nuclear protein EBNA2 after infection with a ΔBNRF1 virus compared to wild-type infection. Likewise, ΔBNRF1 viruses transformed primary B cells much less efficiently than EBV-wt or BNRF1 trans-complemented viruses. We conclude from these findings that BNRF1 plays an important role in viral transport from the endosomes to the nucleus.

scholarly journals Emergence of Secretion-Defective Sublines of Pseudomonas aeruginosa PAO1 Resulting from Spontaneous Mutations in the vfr Global Regulatory Gene

2008 ◽  
Vol 74 (6) ◽  
pp. 1902-1908 ◽  
Author(s):  
Áine Fox ◽  
Dieter Haas ◽  
Cornelia Reimmann ◽  
Stephan Heeb ◽  
Alain Filloux ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Extracellular Enzymes ◽  
Spontaneous Mutation ◽  
Regulatory Gene ◽  
Selective Advantage ◽  
Wild Type ◽  
Strain Pao1 ◽  
Cultivation In Vitro

ABSTRACT Pseudomonas aeruginosa undergoes spontaneous mutation that impairs secretion of several extracellular enzymes during extended cultivation in vitro in rich media, as well as during long-term colonization of the cystic fibrosis lung. A frequent type of strong secretion deficiency is caused by inactivation of the quorum-sensing regulatory gene lasR. Here we analyzed a spontaneously emerging subline of strain PAO1 that exhibited moderate secretion deficiency and partial loss of quorum-sensing control. Using generalized transduction, we mapped the secretion defect to the vfr gene, which is known to control positively the expression of the lasR gene and type II secretion of several proteases. We confirmed this secretion defect by sequencing and complementation of the vfr mutation. In a reconstruction experiment conducted with a 1:1 mixture of wild-type strain PAO1 and a vfr mutant of PAO1, we observed that the vfr mutant had a selective advantage over the wild type after growth in static culture for 4 days. Under these conditions, spontaneous vfr emerged in a strain PAO1 population after four growth cycles, and these mutants accounted for more than 40% of the population after seven cycles. These results suggest that partial or complete loss of quorum sensing and secretion can be beneficial to P. aeruginosa under certain environmental conditions.

The development of tolerance to dodine in Venturia inaequalis

1973 ◽  
Vol 51 (2) ◽  
pp. 379-382 ◽  
Author(s):  
B. H. MacNeill ◽  
Janice Schooley
Keyword(s):  
Venturia Inaequalis ◽  
Spontaneous Mutation ◽  
Free Medium ◽  
Wild Type ◽  
Spontaneous Mutation Rate ◽  
Comparable Level ◽  
Large Numbers ◽  
Screening In Vitro ◽  
Development Of Tolerance

The screening in vitro of large numbers of conidia of Venturia inaequalis against the selection pressure of dodine revealed a spontaneous mutation rate to dodine tolerance of about 1 in 106 conidia screened. Mutants cultured as mycelial disks grew 53–92% as well on a medium containing 0.5 ppm dodine as on a dodine-free medium. A comparable level of tolerance was developed by the wild type after a period of continuous vegetative growth on the dodine medium, but, unlike the mutants, the wild type lost its tolerance when cultured briefly on medium containing no fungicide. One of the seven mutants exhibited the capacity to adapt to increasingly higher concentrations of dodine. It is postulated that the events leading to the development of tolerance to dodine in V. inaequalis may be not only mutational and stable, but also adaptive and reversible, or a combination of both mechanisms.

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