Abstract
Hydrangea macrophylla, renowned for its large inflorescences and a diverse range of colors, highlights a significant limitation in current gene function research, which is the lack of effective molecular genetic tools. This study utilized a tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) system to investigate gene function through posttranscriptional gene silencing in H. macrophylla for the first time. The ortholog of phytoene desaturase (PDS) in H. macrophylla, termed HmPDS, was identified. Infection of tissue-cultured seedlings with TRV-HmPDS led to photobleaching of the leaves. Additionally, infection with TRV containing the HmCHS1 fragment in the flowers resulted in decreased anthocyanin production in sepals and a lightening of sepal coloration in the infected flowers. The phenomena and RT-qPCR results proved that the PDS and CHS genes of hydrangea were successfully silenced via the vacuum infiltration method. Furthermore, the introduction of TRV-HmF3'5'H revealed a decrease in delphinidin-3-glucoside content in sepals and caused a color change in the sepals from blue to pink. This study demonstrated that the TRV-VIGS system was successfully established in H. macrophylla and effectively applied to the function analysis of HmF3'5'H.