A-to-I RNA editing in fungal cell differentiation

• Applicant: Dr. Ines Teichert
• Subject Area: Plant Genetics and Genomics
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405037616

RNA editing is conserved in all biological kingdoms. It is described as the selective insertion, deletion or substitution of nucleotides, leading to a changed transcript sequence. Since this changed transcript could be encoded by the genomic DNA, RNA editing provides a means for gene expression regulation.Editing of adenosine (A) to inosine (I) in protein-coding transcripts is widely distributed in metazoan species. Mammals show mostly editing of non-coding regions, while cephalopods show mostly editing of coding regions, leading to changed protein sequences. Likewise, filamentous fungi belonging to the ascomycetes show A-to-I editing of protein-coding transcript regions. Interestingly, A-to-I editing in these fungi was found to be correlated with sexual fruiting body formation. Possibly, it is required to adapt protein sequences and thus protein function to the formation of progeny, the sexual spores. How A-to-I editing is mediated in fungi is unknown, since homologs to metazoan enzymes do not exist.The aim of this project is to analyze editing sites and gain insight into the fungal editing mechanism. We were able to identify a number of editing events by transcriptome and proteome analysis. Characterization of deletion mutants of affected genes showed that these genes tend to be involved in sexual spore generation. However, the biological significance of many editing sites is still under debate. We want to tackle this question by functional analysis of alleles that are transcribed into the native transcript, a transcript that always contains the changes that would be induced by editing, and a transcript that resembles a non-editable version. To gain insight into the fungal editing mechanism, we have generated a reporter strain that gains an antibiotic resistance when A-to-I editing is induced. Mutagenesis of this strain led to resistant strains that now have to be genetically purified by repeated sexual crosses to the wild type strain. We expect to identify regulators of A-to-I editing or regulatory sites in the editing enzyme by genome sequencing of these strains. In conclusion, the results generated in this project will lead to a deeper understanding of fungal A-to-I RNA editing, and thus to insights into a conserved biological process implicated in human disease.

• DFG Programme: Research Grants