Abstract m 6 A, one of the most abundant mRNA modifications, has been associated with various metabolic processes in plants. Here we show that m 6 A also plays a role in miRNA biogenesis in Arabidopsis thaliana. Significant reductions in plant m 6 A/MTA levels results in lower accumulation of miRNAs whereas pri-miRNA levels tend to be higher in such plants. m 6 A-IP Seq and MTA-GFP RIP were used to show that many pri-miRNAs are m 6 A methylated and are bound by MTA, further demonstrating that pri-miRNAs can also be substrates for m 6 A methylation by MTA. We report that MTA interacts with RNA Pol II, supporting the assumption that m 6 A methylation is a co-transcriptional process, and also identify TGH, a known miRNA biogenesis related protein, as a novel protein that interacts with MTA. Finally, reduced levels of miR393b may partially explain the strong auxin insensitivity seen in Arabidopsis plants with reduced m 6 A levels.

mRNA adenosine methylase (MTA) deposits m6A on pri-miRNAs to modulate miRNA biogenesis in Arabidopsis thaliana