Notes on Genus: Crinivirus

flexuous filaments

Type member: Lettuce infectious yellows virus

Contents

Members of this Genus
General Description
Morphology
Electron Micrograph
Genome
Genus Genomic Organization
Genome Map
Type Member Genomic Organization
All Known Sequences
Curated Sequences

General Description

This is one of three genera in the family Closteroviridae, which are characterised by their very long (950-2000 nm) and very flexuous particles. They were previously classified as closteroviruses but are now classified separately because they have a bipartite genome. Infected plant cells contain massive particle aggregates, often organized into banded inclusions. The name is derived from the Latin crinis, = hair.

Morphology

Virions filamentous, not enveloped, very flexuous, 950-2000 nm long and 10-13 nm in diameter. There is a distinct virion tail. Symmetry helical, with pitch of 3.4-3.7 nm.

Virions composed of 5% nucleic acid.

Genome

Bipartite, linear, single-stranded, positive sense RNA 15,000 to 20,000 nucleotides long. There are sequences with potential hairpin structure near the 3'-end. The 3' terminus has no poly(A) tract and the 5' terminus probably has a methylated nucleotide cap.

Genus Genomic Organization

The genome organisation is broadly similar to the closteroviruses but divided between two RNAs. RNA1 has three or four ORFs, including those involved in virus replication. RNA2 has five or six ORFs, including a heat shock protein homologue and two coat proteins. The ORFs are translated from a set of overlapping, 3'-coterminal subgenomic RNAs.

Type Member Genomic Organization

The RNA is translated from eight open reading frames:
RNA1 has 3 ORFs:
1   217 kDa Polyprotein ORF1a, containing a methyltransferase motif
2 55 kDa Polymerase ORF 1b probably expressed by ribosomal frameshift with ORF1a
3 32 kDa unknown function
RNA2 has 5 ORFs:
4 62 kDa heat-shock protein analogue
5 59 kDa unknown function
6 28 kDa Coat protein
7 52 kDa Minor coat protein
8 26 kDa unknown function