Abstract
DNA-dependent RNA polymerases (Pols) transfer the genetic information stored in genomic DNA to RNA in all organisms. In eukaryotes, the typical products of nuclear Pol I, Pol II, and Pol III are ribosomal RNAs, mRNAs, and transfer RNAs, respectively. Intriguingly, plants possess two additional Pols, Pol IV and Pol V, which produce small RNAs and long noncoding RNAs, respectively, mainly for silencing transposable elements. The five plant Pols share some subunits, but their distinct functions stem from unique subunits that interact with specific regulatory factors in their transcription cycles. Here, we summarize recent advances in our understanding of plant nucleus-localized Pols, including their evolution, function, structures, and transcription cycles.