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Ines Teichert, Tim Alexander Dahlmann, Ulrich Kück, Minou Nowrousian

• RNA editing is a post-transcriptional process that modifies RNA molecules leading to transcript sequences that differ from their template DNA. A-to-I editing was found to be widely distributed in nuclear transcripts of metazoa, but was detected in fungi only recently in a study of the filamentous ascomycete \(\textit {Fusarium graminearum}\) that revealed extensive A-to-I editing of mRNAs in sexual structures (fruiting bodies). Here, we searched for putative RNA editing events in RNA-seq data from \(\textit {Sordaria macrospora}\) and \(\textit {Pyronema confluens}\), two distantly related filamentous ascomycetes, and in data from the Taphrinomycete \(\textit {Schizosaccharomyces pombe }\). Like \(\textit {F. graminearum, S. macrospora }\) is a member of the Sordariomycetes, whereas \(\textit {P. confluens}\) belongs to the early-diverging group of Pezizomycetes. We found extensive A-to-I editing in RNA-seq data from sexual mycelium from both filamentous ascomycetes, but not in vegetative structures. A-to-I editing was not detected in different stages of meiosis of \(\textit {S. pombe}\). A comparison of A-to-I editing in \(\textit {S. macrospora}\) with \(\textit {F. graminearum}\) and \(\textit {P. confluens}\), respectively, revealed little conservation of individual editing sites. An analysis of RNA-seq data from two sterile developmental mutants of \(\textit {S. macrospora}\) showed that A-to-I editing is strongly reduced in these strains. Sequencing of cDNA fragments containing more than one editing site from \(\textit {P. confluens}\) showed that at the beginning of sexual development, transcripts were incompletely edited or unedited, whereas in later stages transcripts were more extensively edited. Taken together, these data suggest that A-to-I RNA editing is an evolutionary conserved feature during fruiting body development in filamentous ascomycetes.