Published in:
01-02-2011 | Annotated Sequence Record
Complete genome sequence of the first endornavirus from the ascocarp of the ectomycorrhizal fungus Tuber aestivum Vittad.
Authors:
Benjamin Stielow, Hans-Peter Klenk, Wulf Menzel
Published in:
Archives of Virology
|
Issue 2/2011
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Excerpt
The genus
Endornavirus was recently approved by the International Committee on Taxonomy of Viruses (ICTV) [
1,
10] to be separated from the family
Partitiviridae, and endornaviruses have only been described in plants and fungi [
4,
15]. They share common properties such as symptom-free infection of their host, occurrence in low-copy number in host cells, lack of true virions [
7], and an efficient vertical transmission in their hosts [
16]. Endornaviruses have unique plasmid-like properties that differ markedly from those of other conventionally encapsidated viruses [
5,
12,
16]. The genomes of endornaviruses consist of linear double-stranded RNA (dsRNA) with a characteristic, single open reading frame (ORF) of up to 18 kb in length, often preceded by a site-specific nick at the 5’ end [
5,
7,
8,
12,
18]. The predicted protein from this ORF harbours in its N-terminal part characteristic amino acid (aa) sequence motifs for viral RNA helicases (VHel) or viral methyltransferases (VMet), while aa sequence motifs for UDP-glycosyltransferases (UGT) and RNA-dependent RNA polymerases (RdRp) are located at close proximity to the 3′ end [
7]. The remaining polyprotein is unrelated to any known functional proteins in the database. Currently, the INSDC databases contain complete sequences of seven endornaviruses. Three are plant-associated viruses infecting cultivated and wild rice (
Oryza sativa endornavirus [OsEV] and
Oryza rufipogon endornavirus [OrEV]) [
5,
11], respectively), as well as broad bean (
Vicia faba endornavirus [VFV]) [
13]. In addition, four fungal isolates are known. One isolate each was reported from the mycelia of the violet root rot fungus (
Helicobasidium mompa endornavirus 1-670 [HmEV1-670]) [
12] and from an informally designated plant-pathogenic oomycete
Phytophtora spp. (Phytophtora endornavirus 1 [PEV1]) [
6], while two isolates originate from the pathogenic ascomycete
Gremmeniella abietina (Gremmeniella abietina type B RNA virus) [
15]
. Here, we report the complete nucleotide sequence of an isolate of a putatively novel species in the genus
Endornavirus from an ectomycorrhizal fungus, isolated from the hypogeous ascomata of a black truffle (
Tuber aestivum Vittad.). Accordingly, we propose the name Tuber aestivum endornavirus (TaEV). The TaEV genome structure is highly similar to that of other
Ascomycetes-infecting endornaviruses, such as Gremmeniella abietina type B RNA virus [
15], containing characteristic motifs for the DEAD-like helicase (DEXDc), VMet and RdRp. …