Silencing of the Chalcone Synthase Gene by a Virus Vector Derived from the Cucumber Mosaic Virus in Petunia

Abstract

Virus-induced gene silencing (VIGS) systems are widely used to downregulate target host genes in plants. The Cucumber mosaic virus (CMV), which has a broad host range, has been used as a VIGS vector system in research. In this study, a VIGS vector system derived from the pepo strain of CMV (CMV pepo) was tested for its use in functional analysis of a target gene in Petunia. The CMV pepo caused systemic infections without severe viral symptoms in petunia plants. A vector containing a short fragment (57 bp) of the chalcone synthase gene (PhCHS-A) was constructed (PhCHSA-CMVpepo) and petunia plants were mechanically inoculated with it. Corollas were white in plants infected with PhCHSA-CMVpepo, but were purple (original color) in plants infected with wild-type CMV pepo. In white corollas, the mRNA level of PhCHS-A was downregulated compared to that in purple corollas. These results indicate that the CMV pepo vector system is useful for VIGS research in flowers of the genera Petunia.