Viruses of plant pathogenic fungi Ghabrial, Said A; Suzuki, Nobuhiro
Annual review of phytopathology,
01/2009, Letnik:
47
Journal Article
Recenzirano
Mycoviruses are widespread in all major groups of plant pathogenic fungi. They are transmitted intracellularly during cell division, sporogenesis, and cell fusion, but apparently lack an ...extracellular route for infection. Their natural host ranges are limited to individuals within the same or closely related vegetative compatibility groups. Recent advances, however, allowed the establishment of experimental host ranges for a few mycoviruses. Although the majority of known mycoviruses have dsRNA genomes that are packaged in isometric particles, an increasing number of usually unencapsidated mycoviruses with positive-strand RNA genomes have been reported. We discuss selected mycoviruses that cause debilitating diseases and/or reduce the virulence of their phytopathogenic fungal hosts. Such fungal-virus systems are valuable for the development of novel biocontol strategies and for gaining an insight into the molecular basis of fungal virulence. The availability of viral and host genome sequences and of transformation and transfection protocols for some plant pathogenic fungi will contribute to progress in fungal virology.
Non-self recognition is a common phenomenon among organisms; it often leads to innate immunity to prevent the invasion of parasites and maintain the genetic polymorphism of organisms. Fungal ...vegetative incompatibility is a type of non-self recognition which often induces programmed cell death (PCD) and restricts the spread of molecular parasites. It is not clearly known whether virus infection could attenuate non-self recognition among host individuals to facilitate its spread. Here, we report that a hypovirulence-associated mycoreovirus, named Sclerotinia sclerotiorum mycoreovirus 4 (SsMYRV4), could suppress host non-self recognition and facilitate horizontal transmission of heterologous viruses. We found that cell death in intermingled colony regions between SsMYRV4-infected Sclerotinia sclerotiorum strain and other tested vegetatively incompatible strains was markedly reduced and inhibition barrage lines were not clearly observed. Vegetative incompatibility, which involves Heterotrimeric guanine nucleotide-binding proteins (G proteins) signaling pathway, is controlled by specific loci termed het (heterokaryon incompatibility) loci. Reactive oxygen species (ROS) plays a key role in vegetative incompatibility-mediated PCD. The expression of G protein subunit genes, het genes, and ROS-related genes were significantly down-regulated, and cellular production of ROS was suppressed in the presence of SsMYRV4. Furthermore, SsMYRV4-infected strain could easily accept other viruses through hyphal contact and these viruses could be efficiently transmitted from SsMYRV4-infected strain to other vegetatively incompatible individuals. Thus, we concluded that SsMYRV4 is capable of suppressing host non-self recognition and facilitating heterologous viruses transmission among host individuals. These findings may enhance our understanding of virus ecology, and provide a potential strategy to utilize hypovirulence-associated mycoviruses to control fungal diseases.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Here, we introduce a new family of eukaryote-infecting single-stranded (ss) DNA viruses that was created recently by the International Committee on Taxonomy of Viruses (ICTV). The family, named
...Genomoviridae
, contains a single genus,
Gemycircularvirus
, which currently has one recognized virus species,
Sclerotinia gemycircularvirus 1
. Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1) is currently the sole representative isolate of the family; however, a great number of SsHADV-1-like ssDNA virus genomes has been sequenced from various environmental, plant- and animal-associated samples, indicating that members of family
Genomoviridae
are widespread and abundant in the environment.
ICTV Virus Taxonomy Profile: Partitiviridae Vainio, Eeva J; Chiba, Sotaro; Ghabrial, Said A ...
Journal of general virology,
01/2018, Letnik:
99, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The Partitiviridae is a family of small, isometric, non-enveloped viruses with bisegmented double-stranded (ds) RNA genomes of 3-4.8 kbp. The two genome segments are individually encapsidated. The ...family has five genera, with characteristic hosts for members of each genus: either plants or fungi for genera Alphapartitivirus and Betapartitivirus, fungi for genus Gammapartitivirus, plants for genus Deltapartitivirus and protozoa for genus Cryspovirus. Partitiviruses are transmitted intracellularly via seeds (plants), oocysts (protozoa) or hyphal anastomosis, cell division and sporogenesis (fungi); there are no known natural vectors. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Partitiviridae, which is available at www.ictv.global/report/partitiviridae.
50-plus years of fungal viruses Ghabrial, Said A; Castón, José R; Jiang, Daohong ...
Virology (New York, N.Y.),
05/2015, Letnik:
479
Journal Article
Recenzirano
Odprti dostop
Abstract Mycoviruses are widespread in all major taxa of fungi. They are transmitted intracellularly during cell division, sporogenesis, and/or cell-to-cell fusion (hyphal anastomosis), and thus ...their life cycles generally lack an extracellular phase. Their natural host ranges are limited to individuals within the same or closely related vegetative compatibility groups, although recent advances have established expanded experimental host ranges for some mycoviruses. Most known mycoviruses have dsRNA genomes packaged in isometric particles, but an increasing number of positive- or negative-strand ssRNA and ssDNA viruses have been isolated and characterized. Although many mycoviruses do not have marked effects on their hosts, those that reduce the virulence of their phytopathogenic fungal hosts are of considerable interest for development of novel biocontrol strategies. Mycoviruses that infect endophytic fungi and those that encode killer toxins are also of special interest. Structural analyses of mycoviruses have promoted better understanding of virus assembly, function, and evolution.
Mycoviruses are thought not to be infectious as free particles and to lack an extracellular phase in their life cycles, limiting the broad use of hypovirulence-associated mycoviruses in controlling ...fungal disease. Here, we demonstrate that purified particles of a DNA mycovirus, Sclerotinia sclerotiorum hypovirulence-associated DNA virus 1 (SsHADV-1), are infectious when applied extracellularly to its host Sclerotinia sclerotiorum . Virus particles isolated from an infected host can infect the hyphae of virus-free S. sclerotiorum directly when applied to hyphae grown on potato dextrose agar or sprayed on leaves of Arabidopsis thaliana and Brassica napus , regardless of vegetative compatibility affiliation. When applied to leaves, the virus can suppress the development of lesions. SsHADV-1 can also reduce disease severity and enhance rapeseed yield significantly under field conditions. SsHADV-1 has a narrow host range; it can infect Sclerotinia minor and Sclerotinia nivalis , sister species of S. sclerotiorum , and cause debilitation of these two fungi, but cannot infect or transfect other tested fungi, such as Botrytis cinerea , which shares the same family with S. sclerotiorum . Virus particles are likely to be very stable on the leaves of A. thaliana plants because viral DNA could be detected at 15 d postinoculation on unwounded leaves and at 10 d postinoculation on wounded leaves, respectively; however, this virus could not infect and move in plant cells. Our findings may prompt a reconsideration of the generalization that mycoviruses lack an extracellular phase in their life cycles and stimulate the search for other DNA mycoviruses with potential use as natural fungicides.
Plant virus-based vectors provide valuable tools for expression of foreign proteins in plants and for gene function studies. None of the presently available virus vectors is suitable for use in ...soybean. In the present study, we produced
Bean pod mottle virus (BPMV)-based vectors that are appropriate for gene expression and virus-induced gene silencing (VIGS) in soybean. The genes of interest were inserted into the RNA2-encoded polyprotein open reading frame between the movement protein (MP) and the large coat protein (L-CP) coding regions. Additional proteinase cleavage sites were created to flank the foreign protein by duplicating the MP/L-CP cleavage site. To minimize the chances of homologous recombination and thus insert instability, we took advantage of the genetic code degeneracy and altered the nucleotide sequence of the duplicated regions without affecting amino acid sequences. The recombinant BPMV constructs were stable following several serial passages in soybean and relatively high levels of protein expression were attained. Successful expression of several proteins with different biological activities was demonstrated from the BPMV vector. These included the reporter proteins GFP and DsRed, phosphinothricin acetyltransferase (encoded by the herbicide resistance
bar gene), and the RNA silencing suppressors encoded by
Tomato bushy stunt virus,
Turnip crinkle virus,
Tobacco etch virus, and
Soybean mosaic virus. The possible use of BPMV as a VIGS vector to study gene function in soybean was also demonstrated with the phytoene desaturase gene. Our results suggest that the BPMV-based vectors are suitable for expression of foreign proteins in soybean and for functional genomics applications.
•Family Partitiviridae has undergone a taxonomic reorganization.•Four new genera of fungal or plant partitiviruses have been added to the family.•The three former genera of fungal or plant ...partitiviruses have been eliminated.•Other recent progress of note in partitivirus research is summarized.•Partitivirus effects on their hosts appear not to be cryptic in many cases.
Phylogenetic analyses have prompted a taxonomic reorganization of family Partitiviridae (encapsidated, bisegmented dsRNA viruses that infect plants, fungi, or protozoa), the focus of this review. After a brief introduction to partitiviruses, the taxonomic changes are discussed, including replacement of former genera Partitivirus, Alphacryptovirus, and Betacryptovirus, with new genera Alphapartitivirus, Betapartitivirus, Gammapartitivirus, and Deltapartitivirus, as well as redistribution of species among these new genera. To round out the review, other recent progress of note in partitivirus research is summarized, including discoveries of novel partitivirus sequences by metagenomic approaches and mining of sequence databases, determinations of fungal partitivirus particle structures, demonstrations of fungal partitivirus transmission to new fungal host species, evidence for other aspects of partitivirus–host interactions and host effects, and identification of other fungal or plant viruses with some similarities to partitiviruses. Some outstanding questions are also discussed.
Double-stranded (ds) RNA fungal viruses are typically isometric single-shelled particles that are classified into three families, Totiviridae, Partitiviridae and Chrysoviridae, the members of which ...possess monopartite, bipartite and quadripartite genomes, respectively. Recent findings revealed that mycovirus-related dsRNA viruses are more diverse than previously recognized. Although an increasing number of viral complete genomic sequences have become available, the evolution of these diverse dsRNA viruses remains to be clarified. This is particularly so since there is little evidence for horizontal gene transfer (HGT) among dsRNA viruses.
In this study, we report the molecular properties of two novel dsRNA mycoviruses that were isolated from a field strain of Sclerotinia sclerotiorum, Sunf-M: one is a large monopartite virus representing a distinct evolutionary lineage of dsRNA viruses; the other is a new member of the family Partitiviridae. Comprehensive phylogenetic analysis and genome comparison revealed that there are at least ten monopartite, three bipartite, one tripartite and three quadripartite lineages in the known dsRNA mycoviruses and that the multipartite lineages have possibly evolved from different monopartite dsRNA viruses. Moreover, we found that homologs of the S7 Domain, characteristic of members of the genus phytoreovirus in family Reoviridae are widely distributed in diverse dsRNA viral lineages, including chrysoviruses, endornaviruses and some unclassified dsRNA mycoviruses. We further provided evidence that multiple HGT events may have occurred among these dsRNA viruses from different families.
Our study provides an insight into the phylogeny and evolution of mycovirus-related dsRNA viruses and reveals that the occurrence of HGT between different virus species and the development of multipartite genomes during evolution are important macroevolutionary mechanisms in dsRNA viruses.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The complete nucleotide sequences of two double-stranded RNA (dsRNA) segments, isolated from the same hypovirulent strain (KL-1) of Sclerotinia sclerotiorum , were determined. Sequence ...analysis showed that dsRNAs 1 to be 2513 nts long and is A–U rich (61.7%). Excluding the poly(A) tail, dsRNAs2 is 2421 nts long and its AU content is 53.1%. The 5′ and 3′-terminal sequences of the positive-strand of each dsRNA could be folded into predicted stable stem–loop structures. Mitochondrial codon usage revealed that each dsRNA has a single large open reading frame coding for a protein containing RNA-dependent RNA polymerase conserved motifs. Furthermore, dsRNAs 1 and 2 share sequence similarities with other mitoviruses. These results suggest that dsRNAs 1 and 2 represent two distinct new mitoviruses, designated S clerotinia s clerotiorum m ito v irus 1 (SsMV1/KL-1) and SsMV2/KL-1, respectively. The hypovirulence traits of strain KL-1 and the two mitoviruses could be co-transmitted to a virus-free virulent strain via hyphal anastomosis.
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