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Ecological aspects of sexual reproduction
Toman, Jan ; Flegr, Jaroslav (advisor) ; Markoš, Anton (referee)
Sexual reproduction is one of the most interesting biological phenomena. No theory has ever entirely explained its wide occurrence among Eukaryotic clades despite its clear disadvantages (e.g. twofold price of sex). Theories can be divided into three groups according to the approach to solve this problem - molecular, genetic and ecological (environmental). Environmental theories are slightly preferred in the last decades and the opinion that the key to the sex enigma lies among them is widely accepted. Most of the environmental theories do not counter each other and there is possibility either to integrate them in several ways or presume that several of these theories might act simultaneously. According to theories, abiotically stable environments without biotic interactions (homogenous) should be suitable for and select for asexual species, whereas environments abiotically variable and rich in biotic interactions (heterogenous) should be suitable for and select for sexual species. The anagenetic phenomenon of punctuated equilibria and some of its explanations, e.g. P. R. Sheldon's Plus ça change hypothesis or J. Flegr's Frozen plasticity theory, also supports this division. There is a vast amount of empirical data supporting this division in ecological studies. Clearly homogenous environments...
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Evolution of the Heme Biosynthetic Pathway in Eukaryotic Phototrophs
CIHLÁŘ, Jaromír
This thesis is devoted to the evolution of the heme biosynthetic pathway in eukaryotic phototrophs with particular emphasis on algae possessing secondary and tertiary red and green derived plastids. Based on molecular biology and bioinformatics approaches it explores the diversity and similarities in heme biosynthesis among different algae. The core study of this thesis describes the heme biosynthesis in Bigelowiella natans and Guillardia theta, algae containing a remnant endosymbiont nucleus within their plastids, in dinoflagellates containing tertiary endosymbionts derived from diatoms called dinotoms, and in Lepidodinium chlorophorum, a dinoflagellate containing a secondary green plastid. The thesis further focusses on new insights in the heme biosynthetic pathway and general origin of the genes in chromerids the group of free-living algae closely related to apicomplexan parasites.
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Ecological aspects of sexual reproduction
Toman, Jan ; Flegr, Jaroslav (advisor) ; Markoš, Anton (referee)
Sexual reproduction is one of the most interesting biological phenomena. No theory has ever entirely explained its wide occurrence among Eukaryotic clades despite its clear disadvantages (e.g. twofold price of sex). Theories can be divided into three groups according to the approach to solve this problem - molecular, genetic and ecological (environmental). Environmental theories are slightly preferred in the last decades and the opinion that the key to the sex enigma lies among them is widely accepted. Most of the environmental theories do not counter each other and there is possibility either to integrate them in several ways or presume that several of these theories might act simultaneously. According to theories, abiotically stable environments without biotic interactions (homogenous) should be suitable for and select for asexual species, whereas environments abiotically variable and rich in biotic interactions (heterogenous) should be suitable for and select for sexual species. The anagenetic phenomenon of punctuated equilibria and some of its explanations, e.g. P. R. Sheldon's Plus ça change hypothesis or J. Flegr's Frozen plasticity theory, also supports this division. There is a vast amount of empirical data supporting this division in ecological studies. Clearly homogenous environments...
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Lateral gene transfer and its utilisation for the phylogeny of eukaryotes
Novák, Lukáš ; Hampl, Vladimír (advisor) ; Čepička, Ivan (referee)
Lateral gene transfer is a relatively rare event in eukaryotes. Presence of a specific gene acquired by lateral transfer in multiple lineages can be therefore considered to be their common synapomorphy, defining them as a monophyletic group. In contrast to usual phylogenetic methods, this approach can potentially shed light even on the direction of evolution and therefore find the position of a root of a given group of organisms. In the first part of this work I discuss various aspects of lateral gene transfer utilisation in eukaryote phylogeny including advantages and disadvantages against common approaches. In the second part I present particular studies that have recently used this method. Key words: Lateral gene transfer, rare genomic changes, long branch attraction artefact, endosymbiosis, phylogeny, eukaryots, protists.
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Evolution of the tetrapyrrole synthesis in eukaryotes
KOŘENÝ, Luděk
This thesis focuses on the nature of heme metabolism in various eukaryotes. One of the aims was the elucidation of the origin of the unique heme biosynthesis pathway in apicomplexan parasites through a comparative study of their photosynthetic relative Chromera velia combining molecular biology, biochemistry and bioinformatics approach. Using similar strategy, I have also investigated the origin and spatial organization of tetrapyrrole biosynthesis in Euglena gracilis. Based on the phylogenetic data I described the complex evolution of heme metabolism in kinetoplastid flagellates including pathogenic trypanosomes. I revealed that one of them (Phytomonas) does not require heme for viability by the combination of various biochemical and molecular biology experiments and bioinformatic analyses.
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