Towards a plant model for enigmatic U-to-C RNA editing: the organelle genomes, transcriptomes, editomes and candidate RNA editing factors in the hornwort Anthoceros agrestis

New Phytol. 2020 Mar;225(5):1974-1992. doi: 10.1111/nph.16297. Epub 2019 Dec 14.


Hornworts are crucial to understand the phylogeny of early land plants. The emergence of 'reverse' U-to-C RNA editing accompanying the widespread C-to-U RNA editing in plant chloroplasts and mitochondria may be a molecular synapomorphy of a hornwort-tracheophyte clade. C-to-U RNA editing is well understood after identification of many editing factors in models like Arabidopsis thaliana and Physcomitrella patens, but there is no plant model yet to investigate U-to-C RNA editing. The hornwort Anthoceros agrestis is now emerging as such a model system. We report on the assembly and analyses of the A. agrestis chloroplast and mitochondrial genomes, their transcriptomes and editomes, and a large nuclear gene family encoding pentatricopeptide repeat (PPR) proteins likely acting as RNA editing factors. Both organelles in A. agrestis feature high amounts of RNA editing, with altogether > 1100 sites of C-to-U and 1300 sites of U-to-C editing. The nuclear genome reveals > 1400 genes for PPR proteins with variable carboxyterminal DYW domains. We observe significant variants of the 'classic' DYW domain, in the meantime confirmed as the cytidine deaminase for C-to-U editing, and discuss the first attractive candidates for reverse editing factors given their excellent matches to U-to-C editing targets according to the PPR-RNA binding code.

Keywords: Anthoceros agrestis; DYW domain; PPR proteins; PPR-RNA binding code; RNA editing factors; chloroplast DNA; mitochondrial DNA; reverse U-to-C RNA editing.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anthocerotophyta* / metabolism
  • Bryopsida* / genetics
  • Organelles / metabolism
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • RNA Editing / genetics
  • RNA, Plant / genetics
  • RNA, Plant / metabolism
  • Transcriptome / genetics


  • Plant Proteins
  • RNA, Plant

Associated data