Partenaires et organisations internationales
(Anglais)
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Plant Genetic Systems, Gent (B), A. Depicker, u. of Gent (B), John Innes Centre, Norwich (UK), U. of Nottingham (UK), Free University, Amsterdam (NL), Universita 'La Sapienza', Rome (I), Austrian Academy of Sciences, Salzburg (A), u. of York (UK), Friedrich Miescher Institute, Basel (CH), Inst. Jacques Monod-CNRS, Paris (F), Zeneca Agrochemicals, Bracknell (UK), INRA, Versailles (F), Agricultural university, Wageningen (NL)
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Résumé des résultats (Abstract)
(Anglais)
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The aim of this project is to elucidate the molecular mechanism for gene silencing to obtain reliable expression or silencing of transgenes in crop plants. Our contribution is to use chitinase (CHN) and b-1,3-glucanase (GLA) transformants of N. sylvestris as a model for developmentally-regulated, posttransciptional gene silencing (PTGS). Last year, we used cordycepin, an inhibitor of RNA synthesis, to compare the turnover of CHN and GLA RNAs targeted for PTGS with the turnover of transcripts of the nptll gene in the same T-DNA, which is not silenced. Thus, increased RNA degradation associated with PTGS is specific for transcripts of the silent gene. RNA-blot hybridization analyses showed that tissues can accumulate low molecular weight RNAs derived from silent CHN and GLA genes. RNAs of the same size were also detected in high expressing tissues suggesting that target sites for nucleolysis might be the same in silent and high-expressing tissues. The inhibitor of protein synthesis, verrucarin A, which dissociates mRNA from ribosomes, did not affect either the stability or rate of degradation of silenced CHN RNA. This suggests that degradation of CHN RNA does not require continuous association of the RNA with ribosomes.
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