An RdDM-independent function of Pol V transcripts in gene regulation and plant defense
RNA polymerase V (Pol V) and Pol IV are known to be specialized for RNA-directed DNA methylation (RdDM). Here, we report that Pol V, but not Pol IV, regulates hundreds of genes including JA-responsive genes and confers plant defense to Botrytis cinerea and Spodoptera exigua. About half of the Pol V-regulated genes are associated with Pol V transcripts (PVTs). We thus hypothesized that some PVTs could regulate gene expression in an RdDM-independent manner. To test this hypothesis, we studied three PVTs, PVT-ERF5a/b and PVT-ERF6, as models. PVT-ERF5a/b and PVT-ERF6 are transcribed from the upstream regions of ERF5 and ERF6 and positively regulate their transcription, thereby regulating plant defense. We further show that such regulation involves PVT-dependent H3K4me3 deposition and requires the DRD1-DMS3-RDM1 complex that mediates Pol V recruitment to the target loci. Our findings highlight an unprecedented role for PVTs in regulating gene transcription, apart from serving as scaffold RNAs to direct DNA methylation. Overall design: RNA-seq of 2-week-old seedlings of Col-0, nrpd1-3, nrpe1-11