This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 142/2/788    most recent pp.106.083956v2 pp.106.083956v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Bleys, A. Articles by Depicker, A. Search for Related Content PubMed PubMed Citation Articles by Bleys, A. Articles by Depicker, A. Agricola Articles by Bleys, A. Articles by Depicker, A.

SYSTEMS BIOLOGY, MOLECULAR BIOLOGY, AND GENE REGULATION

The Frequency and Efficiency of Endogene Suppression by Transitive Silencing Signals Is Influenced by the Length of Sequence Homology^1,[W]

Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, B–9052 Gent, Belgium

Transitivity, the spread of RNA silencing along primary target sequences, leads to the degradation of secondary targets that have no sequence homology to the initial silencing trigger. We demonstrate that increasing the distance between direct and adjacent target sequences in a transgenic primary target delays the onset of silencing of a secondary target gene. Silencing can spread in a 3' to 5' direction over a distance of at least 500 nucleotides (nt), but this requires consistently more time compared to a distance of 98 nt or 250 nt. The efficiency and frequency of transitive silencing of an endogene depends on the length of its sequence homology with the primary target. With a length of 500 nt, efficient silencing can eventually be established in all plants, whereas lengths of 250 nt and 98 nt homology result in less efficient and less frequent suppression. These results suggest that amplification of secondary small interfering RNAs (siRNAs) is a time-requiring process that gradually expands the population of siRNAs until a steady-state level is reached. Moreover, the length of the sequence homology in the primary target providing secondary siRNAs determines whether this steady-state level readily exceeds the threshold necessary for efficient silencing.

² Present address: Sint-Lieven, Gildestraat 17, B–9000 Gent, Belgium.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Ann Depicker (ann.depicker{at}psb.ugent.be).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.106.083956

^* Corresponding author; e-mail ann.depicker{at}psb.ugent.be; fax 32–9–3313809.

Received May 22, 2006; accepted July 31, 2006; published August 11, 2006.