Virus-Induced Gene Silencing of a NAC Transcription Factor Alters Flower Morphology and Accelerates Flower Senescence in Petunia

Transcription factors play an important role in plant growth and development.  We used the tobacco rattle virus (TRV) based virus-induced gene silencing (VIGS) system as a tool for evaluating the possible regulatory role of NAC transcription factors in petunia petal senescence.  The genes encoding NAC transcription factors were identified from a petunia floral EST database.  Fragments of these genes were isolated and included with a fragment of a gene encoding chalcone synthase (CHS) in the viral vector, and young plants were infected with the viral construct.  The CHS acts as a reporter in our purple-flowered cultivar – white flowers or white sectors on purple flowers indicate where gene-of-interest (GOI) has been silenced.  Silencing one of the petunia NAC transcription factors, homologous to the A. thaliana CUC genes, resulted in petal separation, and petal and anther fusion in the flowers, and early onset of floral senescence.