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A Transcriptionally Active State Is Required for Post-Transcriptional Silencing (Cosuppression) of Nitrate Reductase Host Genes and Transgenes
Hervé Vaucheret, Laurent Nussaume, Jean-Christophe Palauqui, Isabelle Quilléré and Taline Elmayan
The Plant Cell
Vol. 9, No. 8 (Aug., 1997), pp. 1495-1504
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/3870398
Page Count: 10
You can always find the topics here!Topics: Transgenes, Genes, Plants, Genetic loci, RNA, DNA, Nitrates, Plant cells, Haploidy, Transgenic plants
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Using tobacco nitrate reductase cosuppression as a model system of post-transcriptional gene silencing, we analyzed the influence of DNA and RNA dosages both together and independently. For this purpose, zero, one, two, or four active or transcriptionally silenced copies of a cauliflower mosaic virus 35S-Nia2 transgene were combined by transformation and subsequent crosses with zero, one, two, three, or four active, disrupted, or transcriptionally repressed copies of the wild-type host Nia genes. The analysis of the corresponding transgenic lines revealed that (1) the percentage of isogenic plants that are affected by cosuppression depends directly upon the relative dosage of both host gene and transgene; (2) transcriptional silencing of the 35S-Nia transgene impedes cosuppression; and (3) the absence of host gene transcription reduces the frequency of cosuppression or delays its triggering. Taken together, these results indicate that transgene DNA per se is not sufficient to trigger post-transcriptional cosuppression of nitrate reductase host genes and transgenes. The requirement for a transcriptionally active state is discussed with respect to both the RNA dosage and the DNA-DNA pairing hypotheses.
The Plant Cell © 1997 American Society of Plant Biologists (ASPB)