Notes on Genus: Macluravirus

flexuous filaments

Type member: Maclura mosaic 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 the genera in the family Potyviridae. Like the other genera, it is characterised by its flexuous filamentous particles, inclusion bodies in infected plant cells and by having a polyprotein genome strategy. It differs from most of the other genera in having insect transmission, and from the genus Potyvirus in having shorter particles (650-660 nm in length) and apparently smaller genomes. Phylogenetic studies also support the recognition of a distinct genus. As in all the genera except the genus Bymovirus, members have monopartite genomes. It is named after its type member, maclura mosaic virus.

Morphology

Virions filamentous, not enveloped, usually flexuous, 650-660 nm long and 12-15 nm in diameter. Symmetry helical with a pitch of 3.4 nm

Virions composed of 5 % nucleic acid and 95 % protein.

Genome

Monopartite, linear, single stranded, positive sense RNA. The only fully sequenced member has a genome of 8.2 kb. The 3' terminus has a poly(A) tract and the 5' terminus has a genome-linked protein (VPg).

Genus Genomic Organization

The only member of this genus for which there is a complete sequence is Chinese yam necrotic mosaic virus. As in other members of the family Potyviridae, its genome is tranlsated into a single polyprotein, which is subsequently processed into functional products, with the coat protein at the C-terminus. However, it lacks the P1 protein that is present at the N-terminus of the polyprotein in other monopartite membes of the family.

Type Member Genomic Organization

There are only partial sequence data available for the type member. An isolate of Chinese yam necrotic mosaic virus has been fully sequenced and its genome is predicted to be translated into a single polyprotein of 297 kDa, from which an estimated nine functional products are produced by proteolytic processing:
HC-Pro Helper component protease     29 kDa
P3 protein unknown function     35 kDa
'6K1' unknown function    7 kDa
CI Cylindrical inclusion putative helicase     74 kDa
'6K2' unknown function     9 kDa
VPg Genome-linked protein     21 kDa
NIa-Pro Nuclear Inclusion protease     24 kDa
NIb Nuclear Inclusion polymerase     65 kDa
CP coat protein     32 kDa
An additional small ORF (PIPO) is generated by frameshifting within the second (P3) cistron.