Establishment of a Virus-Induced Gene Silencing (VIGS) System in Syringa villosa and Functional Characterization of the Floral Scent-Associated Gene SvTPS3

Functional genomic studies in woody ornamental plants are often constrained by the lack of effective gene function validation tools. Virus-induced gene silencing (VIGS) provides a rapid reverse-genetic approach for functional analysis, particularly in plant species where stable transformation remains challenging. However, a tissue-applicable VIGS system has not yet been established for Syringa villosa, an important woody ornamental species with valuable floral traits. In this study, an Agrobacterium-mediated VIGS system was established and optimized in S. villosa using the phytoene desaturase gene (SvPDS) as a reporter gene. Different inoculation methods and Agrobacterium concentrations were evaluated to determine suitable conditions for gene silencing. Syringe infiltration with an Agrobacterium suspension at an OD600 of 0.8 achieved the highest SvPDS silencing efficiency (80.00%) and showed good applicability for subsequent functional studies. The optimized VIGS system was further extended from vegetative tissues to floral tissues and applied to functional analysis of the candidate terpene synthase gene SvTPS3. Silencing of SvTPS3 significantly reduced transcript abundance and decreased the emission rate of (E)-β-ocimene, the predominant volatile compound in S. villosa flowers. This study establishes a VIGS platform applicable to both vegetative and floral tissues of S. villosa and provides a valuable tool for functional characterization of genes associated with floral traits and secondary metabolism in woody ornamental plants.