Malaria-Parasiten nutzen ein komplexes Repertoire aus Transportern, um sich durch ihren Lebenszyklus hindurch mit Nährstoffen aus Wirtszellen zu versorgen. Der Großteil der 144 Transporter von P. falciparum ist als essenziell für asexuelles Blutwachstum klassifiziert. Meine Hypothese war, dass ein Teil der bisher nicht untersuchten Transporter eine spezifische und essenzielle Rolle in den sexuellen Blutstadien von P. falciparum übernimmt und als Angriffspunkt dienen könnte, um die Transmission der Parasiten zu blockieren. Aus dem Transportom von P. falciparum wurden vielversprechende Gene identifiziert und durch experimentell-genetische Verfahren untersucht. Auf diesem Weg konnte ich einen Defekt bestätigen, der durch Fehlen von PfGEP1 hervorgerufen und bereits in der verwandten Spezies P. yoelii beschrieben wurde. Weder männliche noch weibliche Gametozyten konnten ohne GEP1 in der Lage Gameten bilden. Dies deutet auf eine zentrale Rolle für GEP1 in der Gametozyten-Aktivierung hin. Entsprechend groß ist das Potential, durch spezifische Inhibition von GEP1 die Übertragung von Malaria-Parasiten effizient zu unterbinden. Unterbrechung eines zweiten Gens namens MCP2 hatte keinen Effekt auf die Gametozyten von P. falciparum. Stattdessen wies P. berghei nach Fehlen von MCP2 einen Defekt bei der Sporozoitenbildung im Mitteldarm der Mücke auf. Nur in vereinzelten Oozysten konnten Sporozoiten gefunden werden und die Speicheldrüsen der infizierten Mücken enthielten kaum Sporozoiten. Somit hat die MCP2-Deletion keinen direkten Einfluss auf die Transmission vom Säugetierwirt auf die Mücke, jedoch erscheint MCP2 nötig für die Komplettierung des Lebenszyklus. Zusammenfassend bestätigen meine Daten die These, dass Transporterproteine in mindestens einem Stadium des Lebenszyklus von Plasmodium eine essenzielle Rolle spielen und liefern weitere Einblicke in die Funktion dieser Proteine. / During life cycle progression, Plasmodium parasites rely on a complex repertoire of transporter proteins to supply them with nutrients obtained from their host. Of the 144 transporter proteins annotated in Plasmodium falciparum, the majority has already been deemed likely essential for asexual blood growth. In this thesis, I hypothesized that a part of the unassigned parasitic transportome will be specifically essential to the sexual gametocyte stages and thus could contain transmission blocking targets for future application. The transportome of P. falciparum was screened in silico for potential candidates and the most promising genes were then targeted via a Crispr-Cas9-based disruption approach. Through this, I was able to confirm a defect in gametogenesis caused by disruption of PfGEP1 previously observed in P. yoelii. Both male and female gametocytes lacking GEP1 were unable to produce gametes. Overall, my data indicates that GEP1 plays a central role in the activation process, making it a promising transmission blocking target. Disruption of a second candidate gene called MCP2 did not affect P. falciparum asexual and sexual blood stages. Deletion of its P. berghei ortholog instead resulted in impaired sporozoite formation in the mosquito vector. While parasites lacking PbMCP2 were able to infect mosquito midguts and form oocysts, only few of them appeared to produce midgut sporozoites. Consequently, very few sporozoites colonized mosquito salivary glands. While lack of MCP2 does not seem to affect vertebrate-to-mosquito transmission as anticipated, it appears necessary for life cycle progression. Together, the findings presented here underline the importance of transporter proteins for Plasmodium parasites throughout their life cycle and contribute to our understanding of their roles in the different life cycle stages of malarial parasites.

The genus Eimeria (Apicomplexa, Coccidia) provides a wide range of different species with different hosts to study common and variable features within the genus and its species. A common characteristic of all known Eimeria species is the oocyst, the infectious stage where its life cycle starts and ends. In our study, we utilized Eimeria nieschulzi as a model organism. This rat-specific parasite has complex oocyst morphology and can be transfected and even cultivated in vitro up to the oocyst stage. We wanted to elucidate how the known oocyst wall-forming proteins are preserved in this rodent Eimeria species compared to other Eimeria. In newly obtained genomics data, we were able to identify different gametocyte genes that are orthologous to already known gam genes involved in the oocyst wall formation of avian Eimeria species. These genes appeared putatively as single exon genes, but cDNA analysis showed alternative splicing events in the transcripts. The analysis of the translated sequence revealed different conserved motifs but also dissimilar regions in GAM proteins, as well as polymorphic regions. The occurrence of an underrepresented gam56 gene version suggests the existence of a second distinct E. nieschulzi genotype within the E. nieschulzi Landers isolate that we maintain.

The genus Eimeria (Apicomplexa, Coccidia) provides a wide range of different species with different hosts to study common and variable features within the genus and its species. A common characteristic of all known Eimeria species is the oocyst, the infectious stage where its life cycle starts and ends. In our study, we utilized Eimeria nieschulzi as a model organism. This rat-specific parasite has complex oocyst morphology and can be transfected and even cultivated in vitro up to the oocyst stage. We wanted to elucidate how the known oocyst wall-forming proteins are preserved in this rodent Eimeria species compared to other Eimeria. In newly obtained genomics data, we were able to identify different gametocyte genes that are orthologous to already known gam genes involved in the oocyst wall formation of avian Eimeria species. These genes appeared putatively as single exon genes, but cDNA analysis showed alternative splicing events in the transcripts. The analysis of the translated sequence revealed different conserved motifs but also dissimilar regions in GAM proteins, as well as polymorphic regions. The occurrence of an underrepresented gam56 gene version suggests the existence of a second distinct E. nieschulzi genotype within the E. nieschulzi Landers isolate that we maintain.