Short communicationPhenotypic effects and the quantification of transcript abundance in Petunia hybrida 'Fantasy Blue' with virus-induced GA2ox gene silencing

- A protocol for the virus-induced gene silencing for the GA2ox gene was established in Petunia hybrida.
- The reduction in GA2ox transcript levels was measured by the quantitative RT-PCR.
- Significant increases in stem elongation were observed in Petunia plants with decresed GA2ox transcript levels.

The aim of this study was to establish an efficient virus-induced gene silencing (VIGS) protocol for the gibberellin 2-oxidase gene (GA2ox) in Petunia hybrida 'Fantasy Blue' to measure the reduction in GA2ox transcript levels by quantitative RT-PCR (qRT-PCR) and to investigate the phenotypes of the infected plants. In vitro multiplied Petunia plants were subjected to VIGS using tobacco rattle virus vectors. An 838-bp fragment from the N. tabacum gene (NtGA2ox) was cloned in the TRV2 vector. Control plants were also infected with a TRV2 vector containing a fragment of the E. coli β-glucuronidase (GUS) gene as a nonsense sequence. The abundance of the GA2ox and cyclophylin (for normalization) transcripts was determined by qRT-PCR four weeks after inoculation. Shoot tips with the five youngest leaves were used. Stem lengths were measured weekly from the day of inoculation. After four weeks, significant increases in stem elongation were observed in GA2ox-TRV2-infected plants compared with GUS-TRV2-infected plants. In accordance with this observation, the normalized abundance of the GA2ox transcript in GA2ox-TRV2-infected plants was significantly reduced compared with GUS-TRV2-infected plants.