Characteristics and processing of Pol IV-dependent transcripts in Arabidopsis.

RNAi is a highly conserved machinery in eukaryotes for transcriptional or post-transcriptional silencing. In plants, RNA-directed DNA Methylation (RdDM) pathway deploys small interfering RNAs (siRNAs) to target DNA methylation. This process is initiated by the plant-specific RNA polymerase IV (Pol IV) to produce RNA precursors that are later processed into siRNAs. Until recently, characterization of Pol IV transcript had been difficult due to its presumed rapid turnover. This review summarizes five recent reports on Pol IV-dependent RNAs that explore the biogenesis and features of Pol IV transcripts, as well as alternative dicer-independent processing of Pol IV products.