RESUMO
Phylogenetic analysis of large subunit ribosomal RNA (LSU rRNA or 28S rRNA) gene sequences from free-living predatory flagellates Colpodella angusta, Voromonas pontica, and Alphamonas edax (Apicomplexa) confirms their close relationship with chromerids Chromera velia and Vitrella brassicaformis, which possess a functional photosynthetic plastid. Together these organisms form a sister group to parasitic apicomplexans (coccidians and gregarines, or sporozoans sensu lato). This result agrees with the previous conclusion on monophyly of colpodellids and chromerids (chrompodellids) based on phylogenomic data. The revealed relationships demonstrate a complex pattern of acquisition, loss, or modification of plastids and transition to parasitism during alveolate evolution.
Assuntos
Alveolados/classificação , Alveolados/genética , Filogenia , RNA Ribossômico/genética , Sequência de Bases , Teorema de Bayes , Plastídeos/genética , RNA Ribossômico/classificação , Análise de Sequência de DNARESUMO
Mitotis in the choanoflagellate Monosiga sp. has been studied by electron microscopy for the first time based on serial sections of metaphase and anaphase. The dense metaphase plate is formed by chromosomes at the centre of the nucleus. Spindle poles are located at the opposite sides of this plate. The nuclear envelope is intact except for fenestrae at the poles through which the spindle microtubules from the MTOCs penetrate. The MTOC is formed by the entire flagellar apparatus of the interphase cell, often with an axoneme lying in cytoplasm. At anaphase, the chromosomes move to the poles with different speeds and the nuclear envelope fragments and disappears.
