Open reading frame VIII is not required for viability of cauliflower mosaic virus

Open reading frame (ORF) VIII of cauliflower mosaic virus (CaMV) was analyzed by site-directed mutagenesis in order to investigate its potential function for the viral life cycle. Removal of either the start or the stop codon of ORF VIII, as well as interruption of ORF VIII by a new stop codon, did not affect infectivity. Unlike certain ORF VII mutants all three ORF VIII mutants are stable. Hence the ORF VIII product is not essential and ORF VIII mutations do not have deleterious polar effects on the expression of the downstream ORF V, which codes for the viral protease/reverse transcriptase.