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Mol Cell Biol

Title:		Hypovirulence-associated traits induced by a mycovirus of Cryphonectria parasitica are mimicked by targeted inactivation of a host gene
Author(s):		Zhang L; Churchill AC; Kazmierczak P; Kim DH; Van Alfen NK;
Address:		"Department of Plant Pathology and Microbiology, Texas A&M University, College Station 77843"
Journal Title:		Mol Cell Biol
Year:		1993
Volume:		13
Issue:		12
Page Number:		7782 - 7792
DOI:		10.1128/mcb.13.12.7782-7792.1993
ISSN/ISBN:		0270-7306 (Print) 1098-5549 (Electronic) 0270-7306 (Linking)
Abstract:		"Expression of the Vir2 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 Vir2 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 Vir2 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 Vir2 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 Vir2 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 pycinidum 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"
Keywords:		"Amino Acid Sequence Ascomycota/*genetics/pathogenicity Base Sequence DNA, Fungal/genetics Down-Regulation Gene Amplification Gene Expression *Genes, Fungal *Genes, Mating Type, Fungal *Genes, Viral Molecular Sequence Data Mutation Phenotype RNA, Double-St;"
Notes:		"MedlineZhang, L Churchill, A C Kazmierczak, P Kim, D H Van Alfen, N K eng Research Support, U.S. Gov't, Non-P.H.S. 1993/12/01 Mol Cell Biol. 1993 Dec; 13(12):7782-92. doi: 10.1128/mcb.13.12.7782-7792.1993"