Variability and inheritance of double-stranded RNA viruses in Phaffia rhodozyma

Abstract

The present survey demonstrates polymorphism in both the length and the number of double-stranded RNAs (dsRNAs) among six Phaffia rhodozyma strains. Strains with one-, three- and four-types of dsRNA molecules were found, while two strains proved to be dsRNA-free. Elongated icosahedral virus-like particles (VLPs) 34x26 nm in size were detected in strains carrying four- or three-types of dsRNAs. One 3.7-kb dsRNA molecule was found not to form part of the VLP genome. Transmission of the VLPs of strain ATCC 24203 was followed through the basidiospores during the sexual cycle. Cytoplasmic inheritance was observed.

Characterization of virus-like particles and identification of capsid proteins in Xanthophyllomyces dendrorhous

“…The CP protein participate in cap-snatching mechanism in which m(7)Gp from cap structure of cellular mRNAs is transferred to viral transcripts, required for its stability and efficient translation [8][9][10]. The existence of extrachromosomal dsRNA elements of variable length and cytoplasmic elongated icosahedral VLPs have been described in strains of the basidiomycetous yeast Xanthophyllomyces dendrorhous (formerly Phaffia rhodozyma) [11][12][13]. Recently, three putative totiviruses called XdV-L1A, XdV-L1B, and XdV-L2 were identified in the strain UCD 67-385 of X. dendrorhous, and also two dsRNA molecules (XdRm-S1 and XdRm-S2) that could be satellite viruses [14].…”

Isolation of dsRNA-associated VLPs from the strain Cryptococcus hungaricus CBS 6569

“…dsRNAs were isolated from 4-day-old cells according to a previously published method [11]. Agarose gel electrophoresis was carried out as described [12].…”

dsRNA viruses in Nadsonia fulvescens

“…The smaller one is responsible for mycocin production, while the other encodes the dsRNA-dependent RNA polymerase and the capsid protein for both viruses. In some cases (Dipodascus, Xanthophyllomyces), mycocinogenic activity was not found and the biological role of the dsRNA viruses remains unknown (Nosek et al, 1993;Pfeiffer et al, 1996). The phenotypic consequences of one type of dsRNA in Candida curvata, Wickerhamia fluorescens and Yarrowia lypolitica VLPs are also obscure (Matte et al, 1990;Pospisek et al, 1996;Treton et al, 1985).…”

“…pullulans, X. dendrorhous and N. fulvescens var. elongata) of the yeast community in spring tree exudates (Golubev et al, 2002;Pfeiffer et al, 1996). Samples were negatively stained by 2% uranyl-acetate and examined with a Zeiss OPTON EM902 electron microscope.…”

“…Strains used in this study are listed in Table 1. Total nucleic acid was isolated from 3-day-old cultures (Pfeiffer et al, 1996). No extrachromosomal bands were found in N. commutata strains.…”