The composition of the 12 x 103, 7 X 103, and 25 x 103 polypeptides of the triple-gene block of carlaviruses is very similar to that of comparable polypeptides produced by potexviruses; these polypeptides also have homologies with proteins produced by Barley stripe mosaic virus and Beet necrotic yellow vein virus.

The replicase of carlaviruses is a papain-like proteinase with sequence similarity to comparable replicases of potexviruses, furoviruses, capilloviruses, and tymoviruses, especially the latter which, like that of carlaviruses, is capable of autoproteolysis.

Virions of Narcissus latent virus (NLV) are filamentous and about 650 nm long. It was previously considered to be a carlavirus. However, it differs from carlaviruses in inducing the formation of intracellular inclusions (“pinwheels”) and in having a CP of 46 x 103 it is thus now better placed in the genus Macluravirus (family Potyviridae), together with Maclura mosaic virus, to which it is serologically related.

Brown streak symptoms in cassava (Maniliot esculenta) were previously thought to be induced by a carlavirus tentatively designated Cassava brown streak-associated virus. In recent extensive studies, no carlavirus was detected in affected cassava plants (G.D. Foster, personal communication); such plants, however, consistently contained a newly recognized virus (now designated Cassava brown streak virus; CBSV) which induces the formation of cytoplasmic intracellular inclusions and has filamentous particles containing single-stranded RNA having significant sequence homology with that of Sweet potato mild mottle virus. CBSV is thus probably a species of the genus Ipomovirus (Potyviridae).

Carla: sigla from carnation latent virus.

Brunt, A.A., Foster, G.D., Morozov, S.Yu., and Zavriev, S.K.