Bielefeld, Universiẗat, Diss., 2000.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Euglenophyta are monophyletic group of euglenids defined by presence of green, three membrane- bound plastid which has been aquired via secondary endosymbiosis with chlorophyte alga. Mechanism of transport of nuclear-encoded proteins into this plastid is not yet completely understood. It was observed that the proteins are transported to the outermost plastid membrane in vesicles passing through ER and Golgi, but the mechanism of their recognition and fusion with the target membrane remains unclear. Translocation system of inner two membranes is still completely unknown, regarding the situation in other plastids, it has been proposed that homologues of TOC and TIC complexes are present. In this work we analyzed sequence data from proteome of isolated plastid membranes of model organism Euglena gracilis and transcriptome of E. gracilis and its distant relative Eutreptiella gymnastica. We studied whether they contain proteins potentially involved in transport and homologues of proteins of transport systems known from plastids in other organisms (TOC/TIC, ERAD-like transport, SNARE). However, all our results are negative. It is hard to determine whether these findings indicate the possible absence of TOC and TIC complexes in euglenid plastid, or rather the insufficiency of our data. Powered by TCPDF (www.tcpdf.org)

Euglenophyceae represent a group of unicellular eukaryotic organisms that have gained during their evolution the ability to photosynthesize. They aquired plastids via secondary endosymbiosis with a green alga as the plastid donor. Phylogenetic studies searching for the origin of this organelle revealed the green alga Pyramimonas parkeae from Prasinophytes as the closest known relative to euglenid plastids. Pyramimonas parkeae and Euglena share several genes clusters with unique order of genes in their plastid genomes, which also point to the Pyramimonadales as the donor of the plastids. However, it is posible, that organisms more closely related to euglenid plastids than P. parkeae, occur in the environment. In my diploma thesis I focused on the exploration of diversity of Pyramimonadales and Euglenophyceae in environmental samples. I used several approaches to perform this task. I amplified parts of the plastid genomes in environmental samples by using specific PCR and determined their position in the phylogenetic tree. I also made large-scale phylogenetic analyses based on 16S rRNA and 18S rRNA sequences from representatives of the groups Euglenophyceae, Prasinophytes and environmental samples. The results revealed the presence of a large number of environmental sequences relative to the...

Endosymbiotic gain and transfer of plastids is a widespread evolutionary phenomenon and a major driving force of eukaryotic evolution. The integration of a new organelle is accompanied by changes in its structure, gene content, molecular mechanisms for biogenesis and transport, and re-wiring of the host and organelle metabolic pathways. To understand the course and underlying mechanisms of plastid evolution, it is important to study these processes in variety of secondary algae and notice their differences and similarities. Euglenophytes gained their plastids from green eukaryotic algae after a long history of heterotrophic lifestyle. In my thesis, I participated in analyses of newly generated sequence datasets: transcriptomes of Euglena gracilis and Euglena longa and mass spectrometry-determined proteome of E. gracilis plastid with especial regard to the potential novelties associated with plastid gain and incorporation. In the resulting publications we particularly focus on plastid protein import machinery and targeting signals and report extremely reduced TIC and completely absent TOC in euglenophyte plastid. Using the proteomic dataset, we predict potential novel plastid protein translocases recruited from ER/Golgi and re-analyze plastid signal domains, characterizing previously overlooked...