Development of an efficient virus-induced gene silencing method in petunia using the pepper phytoene desaturase (PDS) gene

Key Message CaPDS gene effectively induced gene silencing in the petunia cultivars, however, higher silencing effectiveness was observed to be limited by genotypes, inoculation methods, plant age, inoculation temperature, and presence of endogenous PhPDS mRNA. Virus-induced gene silencing (VIGS) is widely used for functional analysis of genes in plants. Because of the variation in its effectiveness among plant species, the VIGS system is normally optimized using the phytoene desaturase (PDS) gene as a visible indicator. In this study, we optimized an efficient VIGS system for petunias using the PDS gene isolated from pepper (Capsicum annuum) plants as a visible indicator. Application of the CaPDS gene effectively induced gene silencing in the petunia cultivars Mirage Rose, Mirage Pink, and Picobella Blue. However, silencing effectiveness was observed to be limited by genotypes and inoculation methods; apical meristem application was the appropriate method, whereas the highest silencing effectiveness among the cultivars was found in Picobella Blue. In addition, it was found that higher silencing effectiveness was associated with higher degradation of the endogenous PhPDS mRNA. Moreover, in terms of plant age and temperatures, 3-week-old plants grown at 20 degrees C day/18 degrees C night showed high silencing effectiveness for all cultivars. Taken together, infection of apical meristem of 3-week-old plants grown at 20 degrees C day/18 degrees C night with pTRV2-CaPDS exhibited the highest silencing effectiveness of all cultivars. Therefore, this study indicated the effectiveness of the CaPDS in the VIGS experiment with petunias, as well as the involvement of different factors in the mechanism influencing silencing effectiveness in petunias. These results will enable high-throughput functional analysis of genes associated with commercially important traits in petunias.