A Branched Pathway for Transgene-Induced RNA Silencing in Plants

We propose a branched pathway for RNA silencing in plants

Christophe Béclin; Stéphanie Boutet; Peter Waterhouse; Hervé Vaucheret


Scholarcy highlights

  • IR-PTGS of a GUS Transgene Is Inhibited by Virus Infection Mutations in the SGS2/SDE1, SGS3, and AGO1 genes controlling S-PTGS result in CMV hypersensitivity, indicating that PTGS is a mechanism of resistance against viruses
  • IR-PTGS and Methylation of a GUS Transgene Occurs Efficiently in sgs2, sgs3, and ago1 Mutants The sgs2, sgs3, and ago1 mutations were recovered after mutagenesis followed by a screen based on the reactivation of the PTG-Silenced sense 35S-GUS transgene at the L1 locus
  • These three mutations suppress GUS S-PTGS and impair cosuppression of the nitrate reductase gene and lead to hypersusceptibility toward CMV infection, indicating that SGS2/SDE1, SGS3, and AGO1 genes control S-PTGS ofgenes and CMV tolerance. To investigate whether these genes control IR-PTGS, the transgenic line 6b4 and the sgs2-1, sgs3-1, and ago1-27 mutants carrying the L1 locus were transformed with the ⌬GUS-SUG panhandle construct
  • We further investigated whether SGS2/SDE1, SGS3, and AGO1 genes are required for methylation of the GUS coding sequence induced by S-PTGS and IR-PTGS
  • The percentage of transformants showing more than 99% reduction of GUS activity ranged between 50% and 71% in the four genetic backgrounds, while most of the remaining population showed between 50% and 99% reduction
  • We have shown previously that PTGS of a sense transgene is associated with the methylation of the transcribed region and that the inhibition of S-PTGS in the sgs2, sgs3, or ago1 mutant backgrounds was associated with a strong reduction of cytosine methylation
  • Supplementary Material Supplementary Material including additional Results and Discussion; Experimental Procedures; a figure showing that IR-PTGS of endogenous genes occurs in the sgs2-1, sgs3-1, ago1-27 mutants; and a table showing the proportion of transformants exhibiting IRPTGS of AG, AP1, and CLV3 endogenous genes in wild-type and S-PTGS-deficient mutants background can be found online at http:// images.cellpress.com/supmat/supmatin.htm

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