Silencing in Arabidopsis T-DNA transformants: the predominant role of a gene-specific RNA sensing mechanism versus position effects.
Pronounced variability of transgene expression and transgene silencing are commonly observed among independent plant lines transformed with the same construct. Single-copy T-DNA lines harboring reporter genes of various kind and number under the control of a strong promoter were established in Arabidopsis thaliana for a comprehensive analysis of transgene expression. Characterization of 132 independent transgenic lines revealed no case of silencing as a result of site of T-DNA integration. Below a certain number of identical transgenes in the genome, gene copy number and expression were positively correlated. Expression was high, stable over all generations analyzed, and of a comparable level among independent lines harboring the same copy number of a particular transgene. Conversely, RNA silencing was triggered if the transcript level of a transgene surpassed a gene-specific threshold. Transcript level-mediated silencing effectively accounts for the pronounced transgene expression variability seen among transformants. It is proposed that the RNA sensing mechanism described is a genome surveillance system that eliminates RNA corresponding to excessively transcribed genes, including transgenes, and so plays an important role in genome defense.
Schubert
Daniel
D
Max-Planck-Institut für Molekulare Pflanzenphysiologie, 14476 Golm, Germany.
Lechtenberg
Berthold
B
Forsbach
Alexandra
A
Gils
Mario
M
Bahadur
Sultan
S
Schmidt
Renate
R
D017360:Arabidopsis / Q000235:genetics*; D017796:Caulimovirus / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics*; D020868:Gene Silencing; D018745:Genome, Plant; D030821:Plants, Genetically Modified / Q000235:genetics; D011401:Promoter Regions, Genetic; D019076:Transgenes
D004269:DNA, Bacterial; C036483:T-DNA