N4-acetylation of cytidine in mRNA plays essential roles in plants

The base modification N4-acetylation of cytidine in RNA is essential for microRNA biogenesis as well as leaf and embryo development in plants. The biological function of RNA can be modulated by base modifications. Here, we unveiled the occurrence of N4-acetylation of cytidine in plant RNA, including mRNA, by employing LC-MS/MS and acRIP-seq. We identified 325 acetylated transcripts from the leaves of 4-week-old Arabidopsis (Arabidopsis thaliana) plants and determined that 2 partially redundant N-ACETYLTRANSFERASEs FOR CYTIDINE IN RNA (ACYR1 and ACYR2), which are homologous to mammalian NAT10, are required for acetylating RNA in vivo. A double-null mutant was embryo lethal, while eliminating 3 of the 4 ACYR alleles led to defects in leaf development. These phenotypes could be traced back to the reduced acetylation and concomitant destabilization of the transcript of TOUGH, which is required for miRNA processing. These findings indicate that N4-acetylation of cytidine is a modulator of RNA function with a critical role in plant development and likely many other processes.

Automated summary

This study reveals the occurrence of N4-acetylation of cytidine in plant RNA and identifies two N-ACETYLTRANSFERASEs FOR CYTIDINE IN RNA (ACYR1 and ACYR2) that are essential for plant development. Mutations in these genes result in defects in leaf and embryo development due to reduced acetylation and destabilization of the TOUGH transcript. These findings highlight the critical role of N4-acetylation of cytidine in plant development.