Cauliflower Mosaic Virus as a probe for studying gene expression in plants

Abstract

Cauliflower Mosaic Virus (CaMV) represents a natural set of cloned genes, which have to replicate and be expressed in plant cells. Because CaMV DNA cloned in a plasmid is infectious, the viral genome can be assayed for dispensable regions and used as an episomal vector for the introduction and expression of foreign genes in host plants; however, its usefulness is restricted by the limited payload it can accommodate and by the existence of a reverse transcription step in the viral replication cycle. Direct gene transfer and viral infection mediated by Agrobacterium have now extended the possibilities of manipulating CaMV DNA to non‐hosts and allowed regeneration of transgenic plants, which should permit dissection of the functions of the various viral genes. Analysis of CaMV promoters has also defined enhancer sequences that maximize expression of foreign genes in transgenic plants. Finally, the translational strategy of CaMV is now being investigated by direct introduction into protoplasts of DNA constructs that contain combinations of sequences thought to regulate translation of the viral transcripts.