On the stability of sequences inserted into viral genomes

Willemsen, Anouk; Zwart, Mark P

When inserting sequences into the genome of maize streak virus (MSV, Geminiviridae), the infection efficiency decreased as the size of the insert increased (Shen and Hohn 1991) . Although, some of the MSV mutants obtained deletions and reverted to the wildtype length, the frequency of the deletion process did not increase linearly with the size of the insert, but rather depended on the nature of the sequence (Shen and Hohn 1991) . Deletion mutants of the African cassava mosaic virus (ACMV) have also shown to revert back to the original wild-type genome length through recombination between the two components of the bipartite genome (Etessami, Watts, and Stanley 1989) . The selection pressure on the reversion to wild-type genome length is probably a strong size constraint on encapsidation, where in the case of ACMV the size of encapsidated DNA determines the multiplicity of geminivirus particles (Frischmuth, Ringel, and Kocher 2001) .