Presence of double-stranded RNA and virus-like particles in Phaffia rhodozyma.
Four double-stranded RNA (dsRNA) molecules were isolated from Phaffia rhodozyma UCD 67-385. Their molecular sizes were approximately 4.3, 3.1, 0.9 and 0.75 kilobase pairs (kbp) as determined by agarose-gel electrophoresis and they were designated as L, M, S1 and S2, respectively. By differential centrifugation in sucrose gradients, these dsRNAs copurified with isometric virus-like particles 36 nm in diameter. A cured strain, UV-S2, lacking the S2-dsRNA was obtained from P. rhodozyma UCD 67-385 by ultraviolet (UV) light treatment. UV-S2 strain contains identical virus-like particles to those from the wild-type strain, as determined by electron microscopy, suggesting that the S2-dsRNA was not essential for the expression of mycovirus structural polypeptides. On the other hand, both the UCD 67-385 and UV-S2 strains were able to kill P. rhodozyma UCD 67-383, a strain without dsRNAs. These results suggest that the dsRNA molecules also encode a killer system. Finally, the UV-S2 strain maintains killer ability, which suggests that S2-dsRNA is not involved in the killer phenotype expression.
Castillo
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Departamento de Química, Facultad de Ciencia, Universidad de Santiago de Chile.
Cifuentes
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D005111:Extrachromosomal Inheritance; D007181:Inclusion Bodies, Viral / Q000648:ultrastructure*; D055646:Killer Factors, Yeast; D008854:Microscopy, Electron; D003904:Mitosporic Fungi / Q000235:genetics* / Q000648:ultrastructure / Q000821:virology*; D008970:Molecular Weight; D009183:Mycotoxins / Q000235:genetics; D010641:Phenotype; D012330:RNA, Double-Stranded / Q000235:genetics* / Q000302:isolation & purification*; D012331:RNA, Fungal / Q000235:genetics* / Q000302:isolation & purification*
D055646:Killer Factors, Yeast; D009183:Mycotoxins; D012330:RNA, Double-Stranded; D012331:RNA, Fungal