Cauliflower Mosaic Virus - Genome

Genome

The promoter of the 35S RNA is a very strong constitutive promoter responsible for the transcription of the whole CaMV genome. It is well known for its use in plant transformation. It causes high levels of gene expression in dicot plants. However, it is less effective in monocots, especially in cereals. The differences in behavior are probably due to differences in quality and/or quantity of regulatory factors. The promoter was named CaMV 35S promoter ("35S promoter") because the coefficient of sedimentation of the viral transcript, whose expression is naturally driven by this promoter, is 35S. It is one of the most widely used, general-purpose constitutive promoters. It was discovered at the beginning of the 1980s, by Chua and collaborators at the Rockefeller University.

The 35S RNA is particularly complex, containing a highly structured 600 nucleotide long leader sequence with six to eight short open reading frames (ORFs) (Fütterer et al., 1988; Pooggin et al., 1998).

This leader is followed by seven tightly arranged longer ORFs that encode all the viral proteins (reviewed by Hohn and Fütterer, 1997). The mechanism of expression of these proteins is very special. The ORF VI protein (encoded by the 19S RNA) controls translation reinitiation of major open reading frames on the polycistronic 35S RNA, which is normally only happens on bacterial mRNA's. TAV function depends on its association with polysomes and eukaryotic initiation factor eIF3 (Park et al., 2001).

• ORF I - Movement protein
• ORF II - Insect transmission factor
• ORF III - the protein translated shows a non-specific DNA binding activity. it is a structural protein in virus particle.
• ORF IV - Capsid protein
• ORF V - Protease, reverse transcriptase and RNaseH
• ORF VI - Translational activator / Inclusion body protein
• ORF VII - Unknown (dispensable)