| The advent of the virus---induced gene silencing WIGS) strategy, a homology based, sequence specific defense mechanism is a versatile reverse genetics tool. The technique has enabled gene functional studies in a wide array of non-model plants where stable transformation systems would be inapplicable. This study explores the novel application of VIGS to Fedia cornucopiae, (Valerianaceae, Dipsacales). The tobacco rattle virus (TRV) vector, a bipartite RNA virus, was used to down-regulate gene expression by infecting plants with the TRV2, which bears a fragment of the target gene and TRV I. Down-regulation was confirmed by RT-PCR and qRT-PCR to detect relative changes in transcript abundance. Light and scanning electron microscopy were used to examine morphological differences between wild-type and VIGS-treated tissues. Initial experiments focused on the phytoene desaturase (PDS) gene, which has been used as marker in a wide array of plant species across monocots, basal and core eudicots. VIGS was used to downregulate PDS in F. cornucopiae as well as in one other genus in Valerianaceae using a heterologous gene silencing approach. This was achieved by using the FcPDS to silence an ortholog of the gene in Valerianella locusta, an approach that was successful because both orthologs share 90% identity. The technique was subsequently applied to studying the role of the CYCLOIDEA-like paralogs FcCYC1, FcCYC2A, FcCYC2B, FcCYC3A and FcCYC3B. The CYC genes encode transcription factors that are involved in establishing floral symmetry and other morphological traits in plants. In F. cornucopiae, all the paralogs of CYC play a role in flower and stamen development, stamen abortion and maintaining dorsal petal identity. In addition to those roles, CYC3A seems to play a role in ventral patterning. These findings predict that the paralogs are co-opted in flower development and maintaining bilateral symmetry in F. cornucopiae. . |
