Elena Lesch (Bonn University)
PPR78 is responsible for C-to-U RNA editing in the model moss Physcomitrium patens at two sites: cox1eU755SL and rps14eU137SL. The editing factor remains conserved among mosses even when editing is not needed anymore because a U is already present in the RNA and when editing is completely absent or heavily reduced as here exemplarily shown for Anomodon attenuatus. Editing at another site, ccmFNeU1465RC, was discovered and may explain the retention of functional PPR78 orthologs in these species. Hypnum cupressiforme lacking editing at all sites may be a first candidate where PPR78 is absent. Introducing PPR78 and its targets into the bacterium Escherichia coli led to specific C-to-U editing at all three sites. Graph: Elena Lesch
Elena Lesch's Master thesis was awarded with the Prize for the Best Plant Science Master Thesis, which was carried out at Rheinische Friedrich-Wilhelms-Universität Bonn in the year 2020.
Title: Evolution of moss RNA editing factors and their functions tested in a variety of model systems
The expression of moss RNA editing factors in evolutionary distant model species allows new insights into their mode of operation and into the co-evolution with their targets.
Plant RNA editing induces site-specific conversion of cytidines (C) into uridines (U) in plant chloroplasts and mitochondria. RNA-binding pentatricopeptide repeat (PPR) proteins have the key role of binding to the RNA targets and converting Cs into Us. PPR78 is such a nuclear encoded C-to-U RNA editing factor that targets two mitochondrial RNA editing sites in the cox1- and in the rps14-mRNA in the model moss Physcomitrium patens. Many other moss species were surveyed for the presence of PPR78 and it was found to be conserved even in species, where editing is extremely reduced or not needed at all because Us are already present at these positions (corresponding to thymidine in the genes at the DNA level; see figure). Suspecting a yet unrecognized target site for PPR78 we could successfully predict bioinformatically and subsequently confirm a further editing target in the ccmFN RNA. Moreover, we succeeded to transfer PPR78 into the bacterium Escherichia coli, which was recently established by us as a bacterial model system for RNA editing (Oldenkott et al.[1]). We found that PPR78 could not only perform C-to-U conversions at the previously known editing sites in cox1 and rps14 but also at the newly identified site in ccmFN. Altogether the new data are promising for future attempts to specifically introduce changes to RNA transcript sequences in diverse organisms.
[1] Oldenkott, B., Yang, Y., Lesch, E., Knoop, V., Schallenberg-Rüdinger, M. (2019): Plant-type pentatricopeptide repeat proteins with a DYW domain drive C-to-U RNA editing in Escherichia coli. Commun Biol 2, 85. https://doi.org/10.1038/s42003-019-0328-3
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Elena Lesch conducted this work at the Institute of Cellular and Molecular Botany in the „Molecular Evolution“ lab under the supervision of Prof. Dr. Volker Knoop and Dr. Mareike Schallenberg-Rüdinger.