Lack of Sequence Homology between Double-stranded RNA from European and American Hypovirulent Strains of Endothia parasitica

L'Hostis, Brigitte; Hiremath, Shiv; Rhoads, Robert E.; Ghabrial, Said A.

doi:10.1099/0022-1317-66-2-351

Cited by 34 publications

(16 citation statements)

References 11 publications

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“…Unfortunately, records identifying exactly which strains were released are incomplete, and the investigators involved are not available (S. L. Anagnostakis, personal communication). Previous studies regarding the interrelatedness of dsRNAs from C. parasitica indicated that dsRNAs from European strains are related to one another, and dsRNAs from several North American strains are related to one another, but that dsRNAs from European strains are not closely related to those from North American strains (L'Hostis et al, 1985 ;Paul et al, 1988).…”

Section: Introductionmentioning

confidence: 99%

A North American hypovirulent isolate of the chestnut blight fungus with European isolate-related dsRNA

Hillman

Tian

Bedker

et al. 1992

Journal of General Virology

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We have synthesized and mapped a cDNA library representing the one major dsRNA element associated with hypovirulence in strain NB58 of the chestnut blight fungus, Cryphonectria (=Endothia) parasitica, which was isolated from recovering chestnut trees in New Jersey, U.S.A. The linear dsRNA has a size of approximately 12-5 kbp and is polyadenylated at the 3' terminus of one strand. Molecular hybridization experiments indicate that there is sequence similarity between the NB58 dsRNA and dsRNAs from European isolates of C. parasitica, but not among dsRNAs of NB58 and those associated with other North American isolates. Hybridization experiments with mapped cDNA clones representing different regions of the 12.5 kbp dsRNA indicate that the termini and the 3'-proximal two-thirds (relative to the plus strand) are more conserved among NB58 and the European isolates than the rest of the 5'-proximal one-third. Nucleotide sequence analysis of the termini of NB58 dsRNA suggests common organizational features between it and the dsRNA from French-derived strain EP713.

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Section: Introductionmentioning

confidence: 99%

A North American hypovirulent isolate of the chestnut blight fungus with European isolate-related dsRNA

Hillman

Tian

Bedker

et al. 1992

Journal of General Virology

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“…The dsRNA virus-like elements associated with different hypovirulent strains of C. parasitica exhibit considerable heterogeneity with respect to genome size, number of dsRNA species, genome concentration, and sequence homology (20,31,34 been sequenced (45,46). The largest dsRNA contains two open reading frames (ORFs) which encode polyproteins that proteolytically process themselves (12,13,46,47).…”

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“…The phenomenon of cytoplasmically transmissible hypovirulence in C. parasitica is one of the best-documented examples of a naturally occurring form of biological control for plant disease. Our studies are directed towards understanding how dsRNA genetic elements in the fungus cause the attendant changes in host phenotype.The dsRNA virus-like elements associated with different hypovirulent strains of C. parasitica exhibit considerable heterogeneity with respect to genome size, number of dsRNA species, genome concentration, and sequence homology (20,31,34 (12,13,46,47). A structural resemblance between hypovirulence-associated dsRNAs and replicative forms of positive-strand RNA virus genomes has been noted (12,22,29,46,51).…”

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Hypovirulence-associated traits induced by a mycovirus of Cryphonectria parasitica are mimicked by targeted inactivation of a host gene.

et al. 1993

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Expression of the Vr2 gene of Cryphonectria parasitica is down-regulated in strains of the fungus containing a double-stranded RNA genetic element that reduces fungal virulence (W. A. Powell and N. K. Van Alfen, Mol. Cell. Biol. 7:3688-3693, 1987). We have sequenced the Vr2 gene and characterized its structure; the mRNA contains a short open reading frame whose product has structural similarities to several fungal pheromones. A null mutant was constructed by homologous recombination to determine the function of the Vr2 gene and whether its disruption resulted in any of the altered phenotypes exhibited by many hypovirulent strains, such as reductions in virulence, pigmentation, and sporulation. The Vr2 null mutant (18dm) exhibited a wild-type phenotype with respect to gross colony morphology, growth rate, pigmentation, asexual spore viability, and virulence in apple fruit and chestnut trees. However, numbers of asexual fruiting bodies (pycnidia) and conidia were reduced significantly in comparison with the wild-type strain EP155/2. In sexual crosses of 18dm with a wild-type strain of the opposite mating type, perithecia (sexual fruiting bodies) developed but were barren. Deletion of the Vr2 gene results in a phenotype that mimics that of many double-stranded-RNA-containing hypovirulent strains; i.e., the null mutant exhibits significant reductions in asexual sporulation and pycnidium production as well as impaired sexual crossing ability. To our knowledge, this is the first report of the partial reproduction of a virus-induced phenotype by deletion of a virus-perturbed host gene.The filamentous fungus Cryphonectnia (Endothia)parasitica (Murr.) Barr is responsible for the chestnut blight disease, which destroyed American chestnut forests over a 40-year period during the early part of this century (reviewed in references 3, 4, and 42). Biological control of C. parasitica and recovery of infected trees has occurred in Europe by the cytoplasmic transmission of double-stranded RNA (dsRNA) genetic elements between fungal strains. These virus-like elements typically confer a reduction in virulence (hypovirulence) to the fungus and are transmitted from hypovirulent to virulent strains during hyphal anastomosis (fusion of hyphae). In addition to hypovirulence, fungal strains harboring these genetic elements may exhibit an altered colony morphology that includes reduced sporulation and changes in pigmentation (21; reviewed in references 4, 33, 42, and 52). Reductions in levels of enzymes such as laccase (9,28,40,41) and cutinase (53) or of metabolites such as oxalate (27, 28) may also occur in hypovirulent strains. The phenomenon of cytoplasmically transmissible hypovirulence in C. parasitica is one of the best-documented examples of a naturally occurring form of biological control for plant disease. Our studies are directed towards understanding how dsRNA genetic elements in the fungus cause the attendant changes in host phenotype.The dsRNA virus-like elements associated with different hypovirulent strains of C. parasiti...

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“…Subsequent studies showed that the hypovirulence phenotype was transmissible by hyphal fusion to virulent strains (1,2,5,6 Correlative evidence strongly suggests that doublestranded RNA (ds RNA) is the cytoplasmic transmissible determinant responsible for hypovirulence in E. parasitica (9)(10)(11). ds RNAs associated with different hypovirulent strains vary with respect to size, concentration, and sequence homology (3,(9)(10)(11)(12). Information concerning the relationship of these ds RNAs to each other, their structural organization, and their role in hypovirulence is limited or nonexistent.…”

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Structural properties of double-stranded RNAs associated with biological control of chestnut blight fungus

Tartaglia

Paul

Fulbright

et al. 1986

Proc. Natl. Acad. Sci. U.S.A.

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Double-stranded RNAs (ds RNAs) are thought to be the cytoplasmic determinants responsible for the phenomenon of transmissible hypovirulence in the chestnut blight fungus Endothiaparasitica [Murr.] Anderson. The three major ds RNA components associated with the North American hypovirulent strain, Grand Haven 2, were characterized with respect to molecular-hybridization specificity and RNase T1-digestion patterns. The large (L-RNA; %9 kilobase pairs) and middle-sized (M-RNA; -3,5 kilobase pairs) ds RNA components cross-hybridized under stringent conditions and exhibited indistinguishable partial and complete RNase T1 digestion patterns relative to their 5' and 3' termini. These results suggest that M-RNA was derived from L-RNA by an internal deletion event. The small (S-RNA; =1 kilobase pair) RNA was unrelated to L-and M-RNA by these criteria. However, all three ds RNA components contained RNase Ti-resistant oli-

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Lack of Sequence Homology between Double-stranded RNA from European and American Hypovirulent Strains of Endothia parasitica

Cited by 34 publications

References 11 publications

A North American hypovirulent isolate of the chestnut blight fungus with European isolate-related dsRNA

A North American hypovirulent isolate of the chestnut blight fungus with European isolate-related dsRNA

Hypovirulence-associated traits induced by a mycovirus of Cryphonectria parasitica are mimicked by targeted inactivation of a host gene.

Structural properties of double-stranded RNAs associated with biological control of chestnut blight fungus

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