OsRecQ1, a QDE-3 homologue in rice, is required for RNA silencing induced by particle bombardment for inverted repeat DNA, but not for double-stranded RNA.

Based on the nucleotide sequence of QDE-3 in Neurospora crassa, which is involved in RNA silencing, rice (Oryza sativa) mutant lines disrupted by the insertion of the rice retrotransposon Tos17 were selected. Homozygous individuals from the M(1) and M(2) generations were screened and used for further analyses. The expression of the gene was not detected in leaves or calli of the mutant lines, in contrast to the wild type (WT). Induction of RNA silencing by particle bombardment was performed to investigate any effects of the OsRecQ1 gene on RNA silencing with silencing inducers of the GFP (green fluorescence protein)/GUS (beta-glucuronidase) gene in the mutant lines. The results showed that OsRecQ1 is required for RNA silencing induced by particle bombardment for inverted-repeat DNA, but not for double-stranded RNA (dsRNA). The levels of transcripts from inverted-repeat DNA were much lower in the mutant lines than those in the WT. Furthermore, no effects were observed in the accumulation of endogenous microRNAs (miR171 and miR156) and the production of the short interspersed nuclear element retroelement by small interfering RNA. On the basis of these results, we propose that OsRecQ1 may participate in the process that allows inverted repeat DNA to be transcribed into dsRNA, which can trigger RNA silencing.