Virus-induced gene silencing in apricot (Prunus armeniaca L.) and Japanese apricot (P. mume Siebold & Zucc.) with the apple latent spherical virus vector system

Apple latent spherical virus (ALSV) vectors have been shown to effectively induce stable virus-induced gene silencing (VIGS) in a wide range of plant species, including rosaceous fruit tree species such as apple (Malus × domestica Borkh.), pear (Pyrus communis L.), and Japanese pear (P. pyrifolia Nakai). In this study, we attempted to develop a VIGS-based gene evaluation system for two Prunus fruit tree species, apricot and Japanese apricot, using ALSV vectors. A partial sequence of the P. armeniaca PHYTOENE DESATURASE (ParPDS) gene was cloned and ligated into the T-DNA region of a binary vector, pBICAL2, designed based on RNA2 of ALSV. The resultant pBICAL2-ParPDS was introduced into a disarmed Agrobacterium strain, EHA105. pBICAL1, a binary plasmid for the expression of ALSV RNA1 in plants, was also introduced into EHA105. Leaves of Nicotiana benthamiana were infected with pBICAL1/EHA105 and pBICAL2-ParPDS/EHA105 simultaneously to produce and amplify recombinant ALSV particles. The amplified ParPDS-ALSV in N. benthamiana was isolated and infected into the cotyledons of apricot and Japanese apricot seedlings by particle bombardment. Although our attempts to infect wild and recombinant ALSVs into Japanese apricot seedlings were unsuccessful, uniform discoloration of the upper leaves, a typical phenotype of PDS knock down, was observed several weeks after inoculation in apricot seedlings. We discuss the possible use of this VIGS-based gene evaluation system in Prunus.