Practice question

Unlike animals and fungi with three nuclear polymerases, flowering plants evolved two additional enzymes through duplication of Pol II subunits, resulting in total five nuclear RNA polymerases designated Pol I, II, III, IV, and V. Pol IV and Pol V are plant-specific, nonessential for viability under laboratory conditions but critical for epigenetic regulation. Pol IV generates precursors for small interfering RNAs that guide DNA methylation, while Pol V produces scaffold transcripts for recruiting Argonaute-siRNA complexes. This expanded set supports transposon silencing and paramutation in plant genomes.