Flavonoid genes in petunia: addition of a limited number of gene copies may lead to a suppression of gene expression.

Abstract

To evaluate the effect of increased expression of genes involved in flower pigmentation, additional dihydroflavonol-4-reductase (DFR) or chalcone synthase (CHS) genes were transferred to petunia. In most transformants, the increased expression had no measurable effect on floral pigmentation. Surprisingly, however, in up to 25% of the transformants, a reduced floral pigmentation, accompanied by a dramatic reduction of DFR or CHS gene expression, respectively, was observed. This phenomenon was obtained with both chimeric gene constructs and intact CHS genomic clones. The reduction in gene expression was independent of the promoter driving transcription of the transgene and involved both the endogenous gene and the homologous transgene. The gene-specific collapse in expression was obtained even after introduction of only a single gene copy. The similarity between the sense transformants and regulatory CHS mutants suggests that this mechanism of gene silencing may operate in naturally occurring regulatory circuits.

A single transgene locus triggers both transcriptional and post-transcriptional silencing through double-stranded RNA production

“…HDGS can occur at the transcriptional level (transcriptional gene silencing; TGS) or at the post-transcriptional level (post-transcriptional gene silencing; PTGS). Founding papers that revealed these phenomena in transgenic plants did not identify the molecular mechanisms (Matzke et al 1989;Linn et al 1990;Napoli et al 1990;Smith et al 1990;van der Krol et al 1990). Indeed, it took almost a decade to implicate doublestranded RNA (dsRNA) as the trigger of HDGS.…”

RNA interference and HIV‐1 infection

“…The pioneering works of van der Krol and Napoli and co-workers [43,44] on plant molecular genetics opened the field of RNAi study. These researchers, when working with petunias, were surprised to find that the introduction of several copies of a 'purple gene' leads to phenotypes of white or patchy flowers, rather than deep purple ones as expected.…”

Efficient cloning system for construction of gene silencing vectors in Aspergillus niger

“…Starting with pioneer studies on post-transcriptional gene silencing (PTGS) phenomena (Napoli et al 1990;van der Krol et al 1990;Romano and Macino 1992), many aspects of PTGS by dsRNA have been elucidated after the first study reporting the concept of dsRNA-mediated gene silencing (Fire et al 1998).…”