In planta agro-infiltration system for transient gene expression in grapevine (Vitis spp.)

Transient expression of foreign genes by Agrobacterium infiltration is a versatile technique that can be used as a rapid tool for functional analysis and gene silencing studies in plants. A reproducible protocol of Agrobacterium-mediated transient gene transfer was developed for gene expression analysis on greenhouse-grown grapevines, as a complementary approach towards functional genomics and alternative to transgenics. Non-detached leaves from green cuttings were used as the target organ and vacuum infiltrated for in planta inoculation with Agrobacterium tumefaciens harboring mgfp ₅-ER gene construct as visual reporter gene. Step-by-step optimization was performed and showed that the quality of greenhouse material as well as agro-infiltration conditions were the major factors which influenced successful gene expression assays. Following the optimized protocol, up to half of the infiltrated leaf surface displayed green fluorescent foci found in the intercoastal areas. Monitoring of transient Green Fluorescent Protein expression daily achieved for 2 weeks post-infiltration with the highest expression level on day 6. Evidence of GFP silencing in transgenic GFP-expressing grapevine via agro-infiltration was found for the first time. The in planta infiltration system described here provides a powerful tool to explore easily gene function in grapevine avoiding tissue culture steps and the labor-intensive generation of transgenic plants.