Silencing signals in plants: a long journey for small RNAs

We review the genes and RNA molecules associated with mobile RNA silencing and discuss the implications and future directions of this recently discovered phenomenon

Attila Molnar

2011

Scholarcy highlights

  • RNA silencing is a nucleotide-sequence-specific gene regulation mechanism that controls development, maintains heterochromatin and defends many eukaryotic organisms against viruses
  • RNA silencing in plants sRNAs are generated from partially or perfectly doublestranded RNA precursors by an RNase III-like nuclease called Dicer or Dicer-like. ey are incorporated into another nuclease named Argonaute and they use Watson-Crick base-pairing to guide the AGO complex to target nucleic acids. e targeting
  • DCL3 produces repeat-associated, transposonspecific and transgene-derived 24-nt small interfering RNAs to induce changes in heterochromatin using precursor doublestranded RNA that are generated by the coordinated action of the plantspecific DNA-dependant RNA polymerase IV and RDR2
  • Using silencĀ­ ing pathway mutants with defective DCL2, DCL3 and DCL4, the enzymes required for the biogenesis of 22-nt and 24-nt siRNAs, as donor and recipient tissue, we demonstrated that transgene-derived and endogenous 22- to 24-nt siRNAs had moved across the graft union from the wild-type shoot to the mutant root
  • We found a strong bias in mobility or stability of the sRNAs towards the coding strand of transgene sRNA and, to a lesser extent, of the mobile phosphoribosylanthranilate isomerase sRNAs
  • To explain the potency of this effect in the green fluorescent protein transgene systems, we propose that the mobile sRNA could initiate an amplification process involving RDRs and secondary RNA production in the recipient tissue

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