Permanent genome modifications in plant cells by transient viral vectors

Endonuclease-mediated induction of genomic double-strand breaks has enabled genome editing in living cells. However, deploying this technology for the induction of gene disruption in plant cells often relies on direct gene transfer of endonuclease (i.e. zinc finger nuclease or homing endonuclease) expression constructs into the targeted cell, followed by regeneration of a mutated plant. Such mutants, even when they have no detectable traces of foreign DNA, might still be classified as transgenic because of the transgenic nature of the endonuclease delivery method. Indirect delivery of endonucleases into target cells by viral vectors provides a unique non-transgenic approach to the production of mutated plants. Furthermore, viral vectors can spread into the growing and developing tissues of infected plants, which could provide a unique opportunity to bypass the regeneration step that is often required in direct gene-transfer methods.