Genetic compartmentalization in the complex plastid of Amphidinium carteraeand. The endomembrane system (ES) in Phaeodactylum tricornutum
Peridinin-containing dinoflagellates are important members of single-celled eukaryotic algae, which arose from an engulfment of an ancient red alga by a so far undefined host cell, a process called secondary endosymbiosis. Their plastids feature a unique membrane architecture and are surrounded by o...
|PDF Full Text
No Tags, Be the first to tag this record!
|Peridinin-containing dinoflagellates are important members of single-celled eukaryotic algae, which arose from an engulfment of an ancient red alga by a so far undefined host cell, a process called secondary endosymbiosis. Their plastids feature a unique membrane architecture and are surrounded by only three membranes. As the reduction of the endosymbiont’s genome and gene transfer from the plastid to the nucleus, the whole plastid genome was reorganized into minicircles coding for genes normally coded on the plastid genome. In order to isolate individual minicircles from one representative peridinin-containing dinoflagellate Amphidinium carterae CCAM0512 a novel transposon-based approach was carried out within this thesis. 89 minicircles were therefore isolated from A. carterae, 18 (20.2 %) are gene-containing minicircles, 71 (79.8 %) are empty minicircles. The 18 gene-containing minicircles are divided into three groups of minicircles, six single-gene minicircles, one two-genes minicircle and one three-genes minicircle. The 71 empty minicircles are divided into six groups. The characteristics of these minicircles and unique features were analyzed in this thesis. In contrast to previously reported organellar RNA editing in peridinin-containing dinoflagellates, no RNA editing was observed on transcripts of minicircles of A. carterae based on the analysis of coding genes. Additionally, the transcription of open reading frames was shown in so-called empty minicircles. Finally, based on the comparison with minicircles and rDNA sequences of three other A. carterae strains, it was speculated that minicircles undergo a rapid evolutionary diversification.
The mechanisms of protein (e.g. vacuolar proteins) transport and sorting have been well-studied in plants, yeast and animals. However, little is known in the diatom P. tricornutum. In order to investigate the protein transport and sorting in P. tricornutum, essential marker proteins have to be established. In this work, the identification of marker proteins in the endomembrane system was based on a combination of in silico search for homologous proteins of P. tricornutum to proteins with known localizations in plants and subsequent in vivo localization studies in P. tricornutum. Several markers for different subcellular compartments were identified including the plasma membrane, two vacuolar-like structures, cER, hER, the nuclear envelope and the second outermost membrane of the complex plastid (PPM). Furthermore, the three parts of the Golgi apparatus and the cytosol could also be marked. These useful subcellular marker proteins are a very important prerequisite for studying the mechanisms of protein transport and sorting in P. tricornutum.