RESUMO
A 5'-terminal region of 1600-1800 base pairs was amplified, cloned, and sequenced in the large subunit rDNA (LSU rDNA) of four species of foraminifera. These sequences were compared with the homologous regions of 16 eukaryotic taxa in order to establish the phylogenetic position of foraminifera. Analysis of 610 unambiguously aligned bases shows that foraminifera branch closely to plasmodial and cellular slime molds in the middle of the eukaryotic tree--that is, much earlier than suggested by the fossil record. These data, the first DNA sequences reported for foraminifera, will help analyze this class of protists and the early evolution of eukaryotes.
Assuntos
DNA Ribossômico/genética , Eucariotos/genética , Filogenia , RNA Ribossômico/genética , Animais , Sequência de Bases , Clonagem Molecular , Sequência Consenso , DNA de Protozoário/genética , DNA de Protozoário/isolamento & purificação , Dados de Sequência Molecular , Ratos/genética , Homologia de Sequência do Ácido NucleicoRESUMO
We have purified the SerH surface antigen of T. thermophila by a novel and simple procedure and produced specific antisera against it. By the use of various immunochemical techniques, we have investigated the intracellular distribution of the antigen and shown that SerH is not only abundant in the cortex but also in the digestive apparatus of the ciliate. In each of these two localizations, SerH occupies a variety of compartments: in the cortex it can be found in the surface coat, the exocytotic mucocysts, the endocytotic parasomal sacs and as an integral protein of the membrane; in the digestive apparatus, SerH is found around ingested bacteria, in the cytoplasm surrounding the cytopharynx and the forming food vacuoles, and, seemingly, as a membrane-associated protein in young food vacuoles. Pulse-chase experiments have shown that feeding dramatically increases the global turnover of SerH. Besides these localizations, SerH is principally found in clumps around dense intracytoplasmic spheres, which could be mucocyst precursors. Indirect evidence is presented that SerH is routed to the peripheral or extracellular compartments via the mucocysts. The antigen is absent from alveolar, nuclear or mitochondrial membranes. We propose that SerH covers any membrane in contact or future contact with the extracellular medium.
