Involvement of small RNAs and role of the qde genes in the gene silencing pathway in Neurospora.

Small RNA molecules have been found to be specifically associated with posttranscriptional gene silencing (PTGS) in both plants and animals. Here, we find that small sense and antisense RNAs are also involved in PTGS in Neurospora crassa. The accumulation of these RNA molecules depends on the presence of functional qde-1 and qde-3 genes previously shown to be essential for gene silencing, but does not depend on a functional qde-2, indicating that this gene is involved in a downstream step of the gene silencing pathway. Supporting this idea, a purified QDE2 protein complex was found to contain small RNA molecules, suggesting that QDE2 could be part of a small RNA-directed ribonuclease complex involved in sequence-specific mRNA degradation.