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Evolutionary Analysis of Cystatins of Early-Emerging Metazoans Reveals a Novel Subtype in Parasitic Cnidarians
KYSLÍK, Jiří
The evolutionary aspects of cystatins are greatly underexplored in early-emerging metazoans. Thus, we surveyed the gene organization, protein architecture, and phylogeny of cystatin homologues mined from 110 genomes and the transcriptomes of 58 basal metazoan species, encompassing free-living and parasite taxa of Porifera, Placozoa, Cnidaria (including Myxozoa), and Ctenophora. We found that the cystatin gene repertoire significantly differs among phyla, with stefins present in most of the investigated lineages but with type 2 cystatins missing in several basal metazoan groups. Similar to liver and intestinal flukes, myxozoan parasites possess atypical stefins with chimeric structure that combine motifs of classical stefins and type 2 cystatins. Other early metazoan taxa regardless of lifestyle have only the classical representation of cystatins and lack multi-domain ones. Our comprehensive phylogenetic analyses revealed that stefins and type 2 cystatins clustered into taxonomically defined clades with multiple independent paralogous groups, which probably arose due to gene duplications. The stefin clade split between the subclades of classical stefins and the atypical stefins of myxozoans and flukes. Atypical stefins represent key evolutionary innovations of the two parasite groups for which their origin might have been linked with ancestral gene chimerization, obligate parasitism, life cycle complexity, genome reduction, and host immunity.
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Bioinformatická a funkční charakterizace taxonomicky omezených genů
KYSLÍK, Jiří
Evolutionary dynamics, generating novel phenotypic traits, embody an essential route to either lineage-specific adaptations or to the creation of endless forms in organisms. Understanding the evolution of such ultimate novelties requires the study of the origin and the role of the functional units in generating unique traits, which represent the taxon-specific genes (TRGs). Myxozoa, the endoparasitic cnidarians, have become a suitable model for the study of evolutionary innovations, with their example of single-celled novelty: polar capsules. This uniquelly evolved structure within the spore stage represents a lineage-specific analogy of cnidarian stinging cells (nematocyst). In Cnidaria, nematocysts contain several uniquely emerged genes, rendering the assembly of this complex structure. The prominent fraction represents minicollagens, extremely shortened structural peptides forming the wall and tubule during the nematocyst development. Unlike in Cnidaria, the role of TRGs such as minicollagens in myxozoan development is unknown. The thesis describes the evolution and functional characterization of minicollagens in Myxozoa. Using the bioinformatics and molecular approaches, we explored the diversity and genomic organization and comprehensively characterized minicollagen gene expressions during myxospore development and localization of minicollagens in the polar capsule.
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Fylogeneze myxozoí založená na genech specifických pro žahavce
KYSLÍK, Jiří
Současná fylogeneze myxozoí spoléhá zejména na jednotlivých 18S rDNA nebo konkatenovaných analýzách omezeného počtu 18S + 28S rDNA a výjimečně EF-2 sekvencí. I když tyto běžně používané markery podporují konkrétní fylogenetické vztahy, nejsou dostatečné k rekonstrukci některých hlavních větvení, které jsou důležité pro pochopení hlavních fylogenetických trendů u skupiny Myxozoa. Tato studie popisuje nové potenciální fylogenetické markery, tzv. nematogalectiny, které jsou specifickými geny vyskytující se pouze u žahavců. Fylogenetická rekonstrukce založená na nematogalectin genech poukázala shodu s fylogenezí na základě 18S rDNA a s konkatenovanými analýzami 18S rRNA a nematogalectinů, které vykazují lepší podporu hlavních uzlů v rámci fylogeneze myxozoí. Nedávno publikovaná data těchto specifických žahavčích genů představují významný pohled do fylogeneze skupiny Myxozoa.
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Nové fylogenetické markery pro rekonstrukci fylogeneze myxozoí
KYSLÍK, Jiří
Phylogenetic placement of the Myxozoa within the Cnidaria is still not clearly understood, although there are many supports of close relationships between Myxozoa and Medusozoa. This thesis addresses the issue of the phylogenetic position of Myxozoa based on mitochondrial genes (rns and NADH 1). Determination of the position and order of these genes in the mitochodrial genome together with results of phylogenetic analysis might be the key for deciphering of myxozoan phylogeny and declare the phylogenetic placement of the Myxozoa within the Cnidaria. Rns was found to be a new promissing phylogenetic marker in the cnidarian phylogeny which may resolve the problem of myxozoan placement.
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