Plant infection by two different viruses induce contrasting changes of vectors fitness and behavior

Abstract Insect-vectored plant viruses can induce changes in plant phenotypes, thus influencing plant?vector interactions in a way that may promote their dispersal according to their mode of transmission (i.e., circulative vs. noncirculative). This indirect vector manipulation requires host?virus?vector coevolution and would thus be effective solely in very specific plant?virus?vector species associations. Some studies suggest this manipulation may depend on multiple factors relative to various intrinsic characteristics of vectors such as transmission efficiency. In anintegrative study, we tested the effects of infection of the Brassicaceae Camelina sativa with the noncirculative Cauliflower mosaic virus (CaMV) or the circulative Turnip yellows virus (TuYV) on the host-plant colonization of two aphid species differing in their virus transmission efficiency: the polyphagous Myzus persicae, efficient vector of both viruses, and the Brassicaceae specialist Brevicoryne brassicae, poor vector of TuYV and efficient vector of CaMV. Results confirmed the important role of virus mode of transmission as plant-mediated effects of CaMV on the two aphid species induced negative alterations of feeding behavior (i.e., decreased phloem sap ingestion) and performance that were both conducive for virus fitness by promoting dispersion after a rapid acquisition. In addition, virus transmission efficiency may also play a role in vector manipulation by viruses as only the responses of the efficient vector to plant-mediated effects of TuYV, that is, enhanced feeding behavior and performances, were favorable to their acquisition and further dispersal. Altogether, this work demonstrated that vector transmission efficiency also has to be considered when studying the mechanisms underlying vector manipulation by viruses. Our results also reinforce the idea that vector manipulation requires coevolution between plant, virus and vector

Virus effects on plant quality and vector behavior are species specific and do not depend on host physiological phenotype

There is growing evidence that plant viruses manipulate host plants to increase transmission-conducive behaviors by vectors. Reports of this phenomenon frequently include only highly susceptible, domesticated annual plants as hosts, which constrains our ability to determine whether virus effects are a component of an adaptive strategy on the part of the pathogen or simply by-products of pathology. Here, we tested the hypothesis that transmission-conducive effects of a virus (Turnip yellows virus [TuYV]) on host palatability and vector behavior (Myzus persicae) are linked with host plant tolerance and physiological phenotype. Our study system consisted of a cultivated crop, false flax (Camelina sativa) (Brassicales: Brassicaceae), a wild congener (C. microcarpa), and a viable F1 hybrid of these two species. We found that the most tolerant host (C. microcarpa) exhibited the most transmission-conducive changes in phenotype relative to mock-inoculated healthy plants: Aphids preferred to settle and feed on TuYV-infected C. microcarpa and did not experience fitness changes due to infection—both of which will increase viruliferous aphid numbers. In contrast, TuYV induced transmission-limiting phenotypes in the least tolerant host (C. sativa) and to a greater degree in the F1 hybrid, which exhibited intermediate tolerance to infection. Our results provide no evidence that virus effects track with infection tolerance or physiological phenotype. Instead, vector preferences and performance are driven by host-specific changes in carbohydrates under TuYV infection. These results provide evidence that induction of transmission-enhancing phenotypes by plant viruses is not simply a by-product of general pathology, as has been proposed as an explanation for putative instances of parasite manipulation by viruses and many other taxa

Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability

The impact of sulphur limitation on the remobilization of endogenous S compounds during the rosette stage of oilseed rape, and the interactions with N availability on these processes, were examined using a long-term 34SO42− labelling method combined with a study of leaf senescence progression (using SAG12/Cab as a molecular indicator) and gene expression of the transporters, BnSultr4;1 and BnSultr4;2, involved in vacuolar sulphate efflux. After 51 d on hydroponic culture at 0.3 mM 34SO42− (1 atom% excess), the labelling was stopped and plants were subject for 28 d to High S-High N (HS-HN, control), Low S-High N (LS-HN) or Low S-Low N (LS-LN) conditions. Compared with the control, LS-HN plants showed delayed leaf senescence and, whilst the shoot growth and the foliar soluble protein amounts were not affected, S, 34S, and SO42− amounts in the old leaves declined rapidly and were associated with the up-regulation of BnSultr4;1. In LS-LN plants, shoot growth was reduced, leaf senescence was accelerated, and the rapid S mobilization in old leaves was accompanied by decreased 34S and SO42−, higher protein mobilization, and up-regulation of BnSultr4;2, but without any change of expression of BnSultr4;1. The data suggest that to sustain the S demand for growth under S restriction (i) vacuolar SO42− is specifically remobilized in LS-HN conditions without any acceleration of leaf senescence, (ii) SO42− mobilization is related to an up-regulation of BnSultr4;1 and/or BnSultr4;2 expression, and (iii) the relationship between sulphate mobilization and up-regulation of expression of BnSultr4 genes is specifically dependent on the N availability

Genome-Wide Identification and Mapping of NBS-Encoding Resistance Genes in Solanum tuberosum Group Phureja

The majority of disease resistance (R) genes identified to date in plants encode a nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain containing protein. Additional domains such as coiled-coil (CC) and TOLL/interleukin-1 receptor (TIR) domains can also be present. In the recently sequenced Solanum tuberosum group phureja genome we used HMM models and manual curation to annotate 435 NBS-encoding R gene homologs and 142 NBS-derived genes that lack the NBS domain. Highly similar homologs for most previously documented Solanaceae R genes were identified. A surprising ∼41% (179) of the 435 NBS-encoding genes are pseudogenes primarily caused by premature stop codons or frameshift mutations. Alignment of 81.80% of the 577 homologs to S. tuberosum group phureja pseudomolecules revealed non-random distribution of the R-genes; 362 of 470 genes were found in high density clusters on 11 chromosomes

Genome-wide identification of NBS-encoding resistance genes in Brassica rapa

Nucleotide-binding site (NBS)-encoding resistance genes are key plant disease-resistance genes and are abundant in plant genomes, comprising up to 2% of all genes. The availability of genome sequences from several plant models enables the identification and cloning of NBS-encoding genes from closely related species based on a comparative genomics approach. In this study, we used the genome sequence of Brassica rapa to identify NBS-encoding genes in the Brassica genome. We identified 92 non-redundant NBS-encoding genes [30 CC-NBS-LRR (CNL) and 62 TIR-NBS-LRR (TNL) genes] in approximately 100 Mbp of B. rapa euchromatic genome sequence. Despite the fact that B. rapa has a significantly larger genome than Arabidopsis thaliana due to a recent whole genome triplication event after speciation, B. rapa contains relatively small number of NBS-encoding genes compared to A. thaliana, presumably because of deletion of redundant genes related to genome diploidization. Phylogenetic and evolutionary analyses suggest that relatively higher relaxation of selective constraints on the TNL group after the old duplication event resulted in greater accumulation of TNLs than CNLs in both Arabidopsis and Brassica genomes. Recent tandem duplication and ectopic deletion are likely to have played a role in the generation of novel Brassica lineage-specific resistance genes

Organization and molecular evolution of a disease-resistance gene cluster in coffee trees

<p>Abstract</p> <p>Background</p> <p>Most disease-resistance (R) genes in plants encode NBS-LRR proteins and belong to one of the largest and most variable gene families among plant genomes. However, the specific evolutionary routes of NBS-LRR encoding genes remain elusive. Recently in coffee tree (<it>Coffea arabica</it>), a region spanning the <it>S</it>_<it>H</it><it>3 </it>locus that confers resistance to coffee leaf rust, one of the most serious coffee diseases, was identified and characterized. Using comparative sequence analysis, the purpose of the present study was to gain insight into the genomic organization and evolution of the <it>S</it>_<it>H</it><it>3 </it>locus.</p> <p>Results</p> <p>Sequence analysis of the <it>S</it>_<it>H</it><it>3 </it>region in three coffee genomes, E^aand C^asubgenomes from the allotetraploid <it>C. arabica </it>and C^cgenome from the diploid <it>C. canephora</it>, revealed the presence of 5, 3 and 4 R genes in E^a, C^a, and C^cgenomes, respectively. All these R-gene sequences appeared to be members of a CC-NBS-LRR (CNL) gene family that was only found at the <it>S</it>_<it>H</it><it>3 </it>locus in <it>C. arabica</it>. Furthermore, while homologs were found in several dicot species, comparative genomic analysis failed to find any CNL R-gene in the orthologous regions of other eudicot species. The orthology relationship among the <it>S</it>_<it>H</it><it>3</it>-CNL copies in the three analyzed genomes was determined and the duplication/deletion events that shaped the <it>S</it>_<it>H</it><it>3 </it>locus were traced back. Gene conversion events were detected between paralogs in all three genomes and also between the two sub-genomes of <it>C. arabica</it>. Significant positive selection was detected in the solvent-exposed residues of the <it>S</it>_<it>H</it><it>3</it>-CNL copies.</p> <p>Conclusion</p> <p>The ancestral <it>S</it>_<it>H</it><it>3</it>-CNL copy was inserted in the <it>S</it>_<it>H</it><it>3 </it>locus after the divergence between Solanales and Rubiales lineages. Moreover, the origin of most of the <it>S</it>_<it>H</it><it>3</it>-CNL copies predates the divergence between <it>Coffea </it>species. The <it>S</it>_<it>H</it><it>3</it>-CNL family appeared to evolve following the birth-and-death model, since duplications and deletions were inferred in the evolution of the <it>S</it>_<it>H</it><it>3 </it>locus. Gene conversion between paralog members, inter-subgenome sequence exchanges and positive selection appear to be the major forces acting on the evolution of <it>S</it>_<it>H</it><it>3</it>-CNL in coffee trees.</p

Cross-Reactivity of Herpesvirus-Specific CD8 T Cell Lines Toward Allogeneic Class I MHC Molecules

Although association between persistent viral infection and allograft rejection is well characterized, few examples of T-cell cross-reactivity between self-MHC/viral and allogeneic HLA molecules have been documented so far. We appraised in this study the alloreactivity of CD8 T cell lines specific for immunodominant epitopes from human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV). CD8 T cell lines were generated after sorting with immunomagnetic beads coated with either pp65495–503/A*0201, BMLF1259–267/A*0201, or BZLF154–64/B*3501 multimeric complexes. Alloreactivity of the CD8 T cell lines against allogeneic class I MHC alleles was assessed by screening of (i) TNF-α production against COS-7 cells transfected with as many as 39 individual HLA class I-encoding cDNA, and (ii) cytotoxicity activity toward a large panel of HLA-typed EBV-transformed B lymphoblastoid cell lines. We identified several cross-reactive pp65/A*0201-specific T cell lines toward allogeneic HLA-A*3001, A*3101, or A*3201. Moreover, we described here cross-recognition of HLA-Cw*0602 by BZLF1/B*3501-specific T cells. It is noteworthy that these alloreactive CD8 T cell lines showed efficient recognition of endothelial cells expressing the relevant HLA class I allele, with high level TNF-α production and cytotoxicity activity. Taken together, our data support the notion that herpes virus-specific T cells recognizing allo-HLA alleles may promote solid organ rejection

Deconstruction of the (Paleo)Polyploid Grapevine Genome Based on the Analysis of Transposition Events Involving NBS Resistance Genes

Plants have followed a reticulate type of evolution and taxa have frequently merged via allopolyploidization. A polyploid structure of sequenced genomes has often been proposed, but the chromosomes belonging to putative component genomes are difficult to identify. The 19 grapevine chromosomes are evolutionary stable structures: their homologous triplets have strongly conserved gene order, interrupted by rare translocations. The aim of this study is to examine how the grapevine nucleotide-binding site (NBS)-encoding resistance (NBS-R) genes have evolved in the genomic context and to understand mechanisms for the genome evolution. We show that, in grapevine, i) helitrons have significantly contributed to transposition of NBS-R genes, and ii) NBS-R gene cluster similarity indicates the existence of two groups of chromosomes (named as Va and Vc) that may have evolved independently. Chromosome triplets consist of two Va and one Vc chromosomes, as expected from the tetraploid and diploid conditions of the two component genomes. The hexaploid state could have been derived from either allopolyploidy or the separation of the Va and Vc component genomes in the same nucleus before fusion, as known for Rosaceae species. Time estimation indicates that grapevine component genomes may have fused about 60 mya, having had at least 40–60 mya to evolve independently. Chromosome number variation in the Vitaceae and related families, and the gap between the time of eudicot radiation and the age of Vitaceae fossils, are accounted for by our hypothesis

In vitro toxicokinetics and analytical toxicology of three novel NBOMe derivatives - Phase I and II metabolism, plasma protein binding, and detectability in standard urine screening approaches studied by means of hyphenated mass spectrometry

Purpose Toxicokinetic studies are essential in clinical and forensic toxicology to understand drug-drug interactions, influence of individual polymorphisms, and elimination routes, as well as to evaluate targets for toxicological screening procedures. An N-(2-methoxybenzyl)-substituted phenethylamines (NBOMe analogues) intake has been associated with severe adverse reactions including deaths. 1-(1-Benzofuran-5-yl)-N-[(2-methoxyphenyl)methyl]propan-2-amine (5-APB-NBOMe), 2-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b′]difuran-4-yl)-N-[(5-chloro-2-ethoxyphenyl)methyl]ethan-1-amine (2C-B-FLY-NB2EtO5Cl), and 2-(8-bromo-2,3,6,7-tetrahydrobenzo[1,2-b:4,5-b′]difuran-4-yl)-N-[(2-methoxyphenyl)methyl]ethan-1-amine (2C-BFLY-NBOMe) are three emerging NBOMe analogues, which have encountered on the drugs of abuse market. So far, their toxicokinetic data are completely unexplored. Methods The study included mass spectrometry-based identification of phase I and II metabolites following exposure to the terminally differentiated human hepatocellular carcinoma cells (HepaRG). The determination of enzymes involved in the major phase I/II metabolic steps and determination of plasma protein binding (PPB) was done. Finally, the evaluation of the toxicological detectability by different hyphenated mass spectrometry techniques in standard urine screening approaches (SUSAs) was investigated. Results The compounds were extensively metabolized in HepaRG cells mainly via O-dealkylation, hydroxylation, glucuronidation, and combinations thereof. CYP1A2, 2D6, 2C8, 2C19, and 3A4, were involved in the initial reactions of all investigated compounds. Glucuronidation of the phase I metabolites – when observed - was mainly catalyzed by UGT1A9. The PPB of all compounds was determined to be > 85%. Only the high-resolution mass spectrometry-based SUSA allowed detection of all compounds in rat urine but only via metabolites. Conclusions The toxicokinetic data provided by this study will help forensic and clinical toxicologists to reliably identify these substances in case of abuse and/or intoxication and will allow them a thorough risk assessment