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Start Over Creator Eliáš, Marek

2. Řád z Chaosu: Rozmanitost protistů z pohledu 21. století

Creator:
Čepička, Ivan, Eliáš, Marek, and Hampl, Vladimír
Type:
article, model:article, and TEXT
Language:
Czech
Description:
Order out of Chaos: the diversity of protists from the perspective of the 21st century. Unicellular eukaryotes, often called protists, remain much less familiar than macroscopic animals or plants, but recent progress in protist biology has revealed that they represent the bulk of the phylogenetic diversity of eukaryotes. Advances in genome sequencing and in methodology of reconstructing phylogenetic relationships from molecular characters have been instrumental in drawing a new consensus of the eukaryotic phylogenetic tree. Although many controversial issues are yet to be sorted out, the best current hypothesis on the eukaryotic tree assumes the existence of five major "kingdoms" called Opisthokonta, Amoebozoa, Excavata, Archaeplastida, and Chromista. While the monophyletic origin of Opisthokonta (including animals and fungi) and Amoebozoa is solidly supported, the remaining three kingdoms are contenious. The notion of the monophyletic Archaeplastida implies that the primary plastid (coming from an endosymbiotic cyanobacterium), evolved only in the common ancestor of green algae and plants, red algae, and an enigmatic algal group called Glaucophyta. The kingdom Chromista is hypothetically derived from a complex creature represented by a host eukaryptic cell bearing a red algal endosymbiont that in some chromists persists to our days as a secondary plastid. One of protist and generally eukaryotic evolurion is an unknown position of the root of the eukaryotic tree. The "unikonts-bikonts" rooting popular in recent years has been eventually shown as groundless, but alternative hypotheses are emerging based on sophisticated analyses of genome sequences.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. Vznik fotosyntetizujících eukaryot ve světle srovnávací genomiky

Creator:
Eliáš, Marek
Type:
article and TEXT
Language:
Czech
Description:
Endosymbiotická teorie poskytla obecné vysvětlení vzniku fotosyntetizujících eukaryot, ale teprve rozvoj srovnávací genomiky a fylogenetiky umožňuje detailní rekonstrukci počáteční fáze endosymbiózy a jednotlivé kroky přeměny endosymbionta ve fotosyntetizující organelu. Volně žijícím prokaryotickým předkem plastidů byla sinice pravděpodobně schopná fixace vzdušného dusíku. Původ hostitelské buňky prvotního symbiotického vztahu se pokoušejí objasnit dvě hypotézy: (1) „plastid-late“ – ke vzniku plastidu došlo u tzv. archeplastidů (zelené řasy a rostliny, ruduchy a glaukofyty) až po jejich odštěpení od ostatních skupin eukaryot; nebo (2) „plastid-early“ – plastid byl přítomen již u předka všech eukaryot, ale některé vývojové linie jej druhotně ztratily (případně posléze opět druhotně získaly). Poslední výsledky srovnávací genomiky se stavějí mírně na stranu „plastid-late“ hypotézy, i když na definitivní soud je stále ještě brzy. and The endosymbiotic theory has provided a general explanation for the origin of photosynthetic eukaryotes, but only progress in comparative genomics and phylogenetics allows for a detailed reconstruction of the early phases of the endosymbiosis and individual steps converting the endosymbiont into a photosynthesising organelle. The free-living ancestor of the plastid was a cyanobacterium probably capable of nitrogen fixation. The origin of the host cell is being explained by two hypotheses: (1) "plastid-late" - the plastid evolved in so-called archaeplastids (green algae and plant, red algae, and glaucophytes) only after they had split from the remaining groups of eukaryotes; or (2) "plastid-early" - the plastid was present already in the common ancestor of all eukaryotes, but some lineages lost it secondarily (and re-gained it secondarily in some cases). The most recent results of comparative genomics slightly favour the "plastid-late" hypothesis, although it is still premature to draw definite conclusions.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/

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