Rapid, high efficiency virus-mediated mutant complementation and gene silencing in .

Background: (snapdragon) species are models for genetic and evolutionary research but recalcitrant to genetic transformation, limiting use of transgenic methods for functional genomics. Transient gene expression from viral vectors and virus-induced gene silencing (VIGS) offer transformation-free alternatives. Here we investigate the utility of Tobacco rattle virus (TRV) for homologous gene expression in and VIGS in and its relative

Results: proved highly susceptible to systemic TRV infection. TRV carrying part of the () gene triggered efficient silencing, visible as tissue bleaching, providing a reporter for the extent and location of VIGS. VIGS was initiated most frequently in young seedlings, persisted into inflorescences and flowers and was not significantly affected by the orientation of the homologous sequence within the TRV genome. Its utility was further demonstrated by reducing expression of two developmental regulators that act either in the protoderm of young leaf primordia or in developing flowers. The effects of co-silencing and the trichome-suppressing () gene from the same TRV genome showed that tissue bleaching provides a useful marker for VIGS of a second target gene acting in a different cell layer. The ability of TRV-encoded H protein to complement the mutant phenotype was also tested. TRV carrying the native coding sequence with to report infection failed to complement mutations and triggered VIGS of in wild-type plants. However, a sequence with 43% synonymous substitutions encoding H protein, was able to complement the mutant phenotype when expressed without a VIGS reporter.

Conclusions: We demonstrate an effective method for VIGS in the model genus and its relative that works in vegetative and reproductive tissues. We also show that TRV can be used for complementation of a loss-of-function mutation in These methods make rapid tests of gene function possible in these species, which are difficult to transform genetically, and opens up the possibility of using additional cell biological and biochemical techniques that depend on transgene expression.