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Evolution of nuclear and plastid genomes in euglenids
Hrdá, Štěpánka ; Hampl, Vladimír (advisor) ; Krajčovič, Juraj (referee) ; Škaloud, Pavel (referee)
Algae form a diverse group of simple photosynthetic eukaryotes of polyphyletic origin. Algae with a primary plastid (Archaeplastida) acquired it by ingesting cyanobacterium, a prokaryote; algae with a complex plastid acquired their plastid by ingesting another eukaryote with a primary or already complex plastid. Algae with a complex plastid are chimeras containing genes derived from the host genome, as well as genes derived from the genome of the endosymbiont, and also genetic material derived from genomes of their previous stable or transient endosymbionts. One of the groups with plastid derived from green algae are euglenophytes. This thesis deals with the genomes of three organisms that represent individual actors in the endosymbiotic process in euglenophytes. These are a heterotrophic host from the class Euglenida, a phototrophic endosymbiont from the class of green algae Prasinophyceae and the resulting phototrophic euglenid from the group Euglenophyceae. Knowledge of their genomes should illuminate the course of endosymbiotic gene transfer (EGT) in the formation of algae with a complex plastid. We annotated the plastid genome of a phototrophic euglenid Eutreptiella gymnastica and published it as the third plastome of Euglenophytes after the iconic and economically important Euglena gracilis...
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The phenomenon of symbiosis and its importance to theoretical biology
Lhotský, Josef ; Markoš, Anton (advisor) ; Neustupa, Jiří (referee) ; Krajčovič, Juraj (referee)
7 Abstract Close physical interspecific associations called symbioses are central for understanding both evolution and interactions of all branches of living creatures, as well as shaping the Earth's physical features - in other words, they are essential for understanding the nature of whole biosphere. Symbiotic research takes place in some variation in all fields of biology, and since the nature of the phenomenon apparently has a fundamental importance as an exceptional underlying & unifying scheme, there is growing need for appropriate theoretical analysis. Here I discuss the theoretical frame, definition and history of the concept of symbiotic interactions and its significance and use in theoretical biology. Keywords: symbiosis, life, microorganisms, evolution, metaphors and models
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The complicated evolution of methionine adenosyltransferase in euglenids and eukaryotes in general
Szabová, Jana ; Hampl, Vladimír (advisor) ; Krajčovič, Juraj (referee) ; Sanchez-Perez, Gabino (referee)
Many eukaryotic genes do not follow vertical inheritance pattern. In the present work, we have chosen as a model the gene for methionine adenosyltransferase (MAT), in which we have decided to examine in detail the evolutionary history. MAT is a ubiquitous essential enzyme that, in eukaryotes, occurs in two relatively divergent paralogs: MAT and MATX. Both paralogs have punctate distributions across the tree of eukaryotes and, except for a few cases, they are mutually exclusive. This points to the complicated evolutionary history of this gene couple, which may be caused by either differential loss of old paralogs or the spread of one of these paralogs by horizontal gene transfer (HGT). We have focused on the evolution of this enzyme particularly within one of the best-known groups of flagellates, the euglenids, because it was hypothesized that MATX evolved in photosynthetic euglenids before it spread to other lineages. We gained 26 new sequences from 23 euglenid lineages and one prasinophyte alga Pyramimonas parkeae. MATX was found only in photoautotrophic euglenids. Both, mixotroph Rapaza viridis and the prasinophyte alga Pyramimonas parkeae, the closest known relative of the euglenid plastid ancestor, only displayed the MAT paralog. In contrast, both paralogues were found in two euglenid species...
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