Conserved key players required for Physcomitrella patens male fertility are affected by accumulation of (epi-) mutations

Physcomitrella patens belongs to the bryophytes and is an extant species of the first land plants. This phylogenetic informative position allows the analysis of key evolutionary steps in (land) plant evolution employing P. patens as a model organism. Decades of research mainly focused on the gametophytic generation, probably also due to the lack of sexual reproductive events in the primarily used ecotype Gransden. Long term in vitro vegetative reproduction probably led to the accumulation of somatic (epi-) mutations which eventually led to a nearly male sterile phenotype. So far, only few P. patens ecotypes are used for scientific work. Thus, to overcome the fertility issues and to apply comparative analyses to study sexual reproduction and sporophyte development as well as species and population divergence in P. patens, the establishment of more ecotypes is highly needed. In comparison to other plant model organisms as e.g. Arabidopsis thaliana, genome wide epigenetic modifications especially with regard to sexual reproduction are still barely studied in P. patens ecotypes. Here I present the characterization of the sexual reproduction of the recently introduced fertile ecotype Reute which was collected 2006 in Germany. Reute is the most closely related ecotype to Gransden reported so far. In a comparative analysis between the ecotypes Gransden, Reute and Villersexel, I could show no differences in timing and morphology of the sexual reproductive tissues. However, while Reute was as fertile as the more distant ecotype Villersexel, Gransden was nearly self-sterile. Also, I present the fluorescent marker strain Reute-mCherry which can be used in crossing analyses e.g. to determine if female or male sexual reproductive organs are impaired. By employing this method, a clear male defect could be shown in Gransden. Further, I present a comparative multi-omics analysis between Gransden and Reute using different tissues during sexual reproduction. Single nucleotide polymorphisms (SNPs), DNA-methylation and RNA-expression pinpoint a flagellar defect, which presumably leads to the observed male fertility impairment in Gransden. Finally, I present the characterization of key-players which are highly conserved within eukaryotes and are required for flagellar motility in humans as well as in the moss P. patens