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

The aim of this study was to establish an efficient virus-induced gene silencing (VIGS) protocol for the gibberellin 2-coddase gene (GA(2)ox) in Petunia hybrida 'Fantasy Blue' to measure the reduction in GA(2)ox 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 (NtGA(2)ox) was cloned in the TRV2 vector. Control plants were also infected with a TRV2 vector containing a fragment of the E. coli beta-glucuronidase (GUS) gene as a nonsense sequence. The abundance of the GA(2)ox and cyclophylin (for normalization) transcripts was determined by gRT-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 GA(2)ox-TRV2-infected plants compared with GUS-TRV2-infected plants. In accordance with this observation, the normalized abundance of the GA(2)ox transcript in GA(2)ox-TRV2-infected plants was significantly reduced compared with GUS-TRV2-infected plants. (C) 2015 Elsevier B.V. All rights reserved.