Showing papers by "Richard A. Jorgensen published in 1998"

An RNA-based information superhighway in plants

Abstract: In their commentary, Jorgensen et al . propose that plants contain a mechanism designed to transfer information over long distances--similar in function to an animal9s bloodstream or nervous system. The authors integrate recent work on a phenomenon called "cosupression," in which introduced genes can suppress expression of the plant9s own genes, with other research on how plants resist viral infections and suggest that information-carrying molecules (likely RNAs) move through the plant in long tubes (phloem) and regulate cell physiology at a distance.

Distinct patterns of pigment suppression are produced by allelic sense and antisense chalcone synthase transgenes in petunia flowers

Abstract: Summary A single-copy sense Chalcone synthase (Chs) transgene driven by a strong promoter and producing a fully translatable transcript was converted to an allelic antisense Chs transgene by Cre-lox-mediated DNA recombination in petunia. The sense Chs allele suppressed flower pigmentation in a simple pattern determined by cells at the junctions between adjacent petals, as is typical of single-copy sense Chs transgenes of this type, whereas the antisense Chs allele produced a different pattern of Chs suppression with white petal edges and reduced pigmentation throughout the petal limbs, as is typical of antisense Chs transgenes. In plants carrying a lox-flanked Chs transgene, the presence of Cre protein can cause both sense-specific and antisense-specific patterns to be superimposed in the same flower, suggesting that sense and antisense suppression by single-copy transgenes are mediated by different mechanisms or occur in different cellular or developmental compartments. The presence of Cre also causes the production of numerous, non-clonal white spots, suggesting that the turnover state is not cell-autonomous.

Homology-based control of gene expression patterns in transgenic petunia flowers.

Abstract: Plant transgenes may participate in two types of homology-based gene silencing. One requires transcript homology, is post-transcriptional, and is referred to as cosuppression; the other requires promoter homology, is transcriptional, and is similar to paramutation. This paper uses flower color transgenes to address the hierarchical operation of both mechanisms in plants carrying two transgene copies. It is shown that cosuppression of homologous, endogenous flower color genes by single-copy transgenes requires that the transgene be driven by a strong promoter and that the degree of cosuppression is highly sensitive to increasing transgene dosage. Together, these observations suggest that cosuppression should be a sensitive reporter of epigenetic changes in transgene transcription, such as might be caused by paramutation-like interactions between transgene loci. Intercrosses bringing together two homologous transgene loci, one a known epimutable reporter and the other a transgene inverted repeat, result in complete loss of cosuppression in some outcross progeny and a qualitative change in morphology-based patterns of cosuppression in other outcross progeny. This paramutation-like behavior suggests that the transgenes may be altered at the transcriptional level, eliminating cosuppression altogether or changing the spatial pattern of transgene transcription to produce a new pattern of cosuppression.