A New Class of Genic Nuclear RNA Species in Arabidopsis

Targeting of Arabidopsis PHABULOSA (PHB) mRNA by miR166 has been implicated in gene body methylation at the PHB locus. We report the surprising finding that the loci encoding PHB and the body-methylated miR414 target eIF2 produce an array of RNA species of discrete sizes. The PHB RNAs are nuclear, and are neither polyadenylated nor capped. Their biogenesis requires neither RNA polymerases IV/V, nor miR166-guided cleavage. Their insensitivity to mutation of the nucleoplasmic exosome suggests that these nuclear RNAs are unlikely to be failed processing products. Our data reveal the existence of a new class of genic nuclear RNA species.