Notes on Genus: Carlavirus

flexuous filaments

Type member: Carnation latent virus

General Description

The genus Carlavirus (carnation latent virus group) is one of the genera in the family Betaflexiviridae and contains a large number of members or tentative members. In genome organisation it particularly resembles the genus Foveavirus and members of the family Alphaflexiviridae and is distinguished from them by having 6 ORFs and a large replication protein. Many of its members are transmitted by aphids in a non-persistent manner. Most members cause relatively mild symptoms.

Morphology

Virions filamentous and slightly flexuous, not enveloped, 610-690 nm long and (10-)12-13(-15) nm in diameter. Nucleocapsids longitudinally striated (files of subunits separated by about four longitudinal furrows); symmetry helical with pitch of 3.3-3.4 nm.

Virions composed of 5-7 % nucleic acid.

Genome

Monopartite, linear, single stranded, positive sense RNA. 8.4-8.7 kb in length. The 3'- terminus has a poly(A) tract and the 5'- terminus sometimes has a methylated nucleotide cap, or a monophosphate.

Genus Genomic Organization

The RNA is translated from six putative open reading frames which are:

1.	219-223 kDa	Polymerase
2.	25-26 kDa		2-4. Triple gene block: probably involved in cell-to-cell movement
3.	11-12 kDa
4.	7-8 kDa
5.	32-36 kDa	Coat protein
6.	11-16 kDa	nucleic acid binding protein (NABP)

Type Member Genomic Organization

There is no complete sequence for this virus, but other members of the genus have genomes of c. 8500 nucleotides. By analogy with other members, the RNA is probably translated from six open reading frames.