Turnip crinkle virus

Turnip crinkle virus (TCV) is a plant pathogenic virus of the family Tombusviridae. It was first isolated from turnip (Brassica campestris ssp. rapa). TCV is a small (4054 base pairs), single-stranded, positive-sense RNA virus (viral RNA is in the same orientation as mRNA). It has been shown to infect various types of plant species (including Nicotiana benthamiana) including the common plant model, Arabidopsis thaliana. Its gRNA encodes for five proteins: p28 and p88 (replication), p8 and p9 (movement) and CP (coat protein or encapsidation). The structure of the virus was determined to 3.2 Ångstrom resolution using x-ray crystallography in 1986. It is structurally quite similar to the tomato bushy stuntvirus.

Replication of the viral RNA begins with the migration of p28 to the mitchondrial membrane. p28 migrates to and invaginates the outer mitochondrial membrane; several p88 molecules are brought the newly formed vesicles. The viral RNA binds to the p28 bound to the membrane and the RNA dependent RNA polymerase, or p88, initiates replication of the positive strand RNA to produce a minus strand intermediate. The negative-strand intermediate is used as a template to produce progeny positive strand RNA. The coat proteins p8, p9, and p38, are involved in movement in the plant.

A number of non-coding RNA elements have been characterised in the TCV genome; examples are hairpin 5 and the core promoter.

Small, helper viruses known as satellite RNA have been found to co-infect plants only in the presence of TCV. These non-coding RNAs up-regulate the symptoms of TCV infection. The satellite RNA are dependent of the TCV and host machinery to propagate. Satellite C shares sequence homology with the 3'end of the TCV, while satellite D shares sequence homology with the 5'end of satellite C.