The ejectisomes of the flagellate Chilomonas paramecium: visualization by freeze-fracture and isolation techniques

The role of microRNAs in diseases and related signaling pathways

MicroRNAs (miRNAs) are epigenetic regulators of the gene expression and act through posttranslational modification. They bind to 3'-UTR of target mRNAs to inhibit translation or increase the degradation mRNA in many tissues. Any alteration in the level of miRNA expression in many human diseases indicates their involvement in the pathogenesis of many diseases. On the other hand, the regulation of the signaling pathways is necessary for the maintenance of natural and physiological characteristics of any cell. It is worth mentioning that dysfunction of the signaling pathways manifests itself as a disorder or disease. The significant evidence report that miRNAs regulate the several signaling pathways in many diseases. Base on previous studies, miRNAs can be used for therapeutic or diagnostic purposes. According to the important role of miRNAs on the cell signaling pathways, this article reviews miRNAs involvement in incidence of diseases by changing signaling pathways.

Ejectisins: tough and tiny polypeptides are a major component of cryptophycean ejectisomes

Fragments of discharged ejectisomes were isolated from two Cryptomonas and a Chroomonas species by detergent treatment followed by Percoll density gradient centrifugation. The fragments withstand high concentrated detergent solutions, reducing agents and freeze-thawing. Disintegration was achieved in 6 M guanidine hydrochloride. Reassembly into long, filamentous, ejectisome-like structures occurred after dialysis. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the polypeptide patterns of isolated ejectisome fragments and of reconstituted ejectisome-like structures were dominated by polypeptides with relative molecular weights of approximately 6 kDa. The polypeptides were not glycosylated and did not cross-react with antisera directed against recombinant Reb polypeptides which constitute the R-bodies of Caedibacter taeniospiralis. A polyclonal antiserum directed against reconstituted, ejectisome-like filaments cross-reacted with the 6-kDa polypeptides and immunolabeled extruded ejectisome filaments. Twenty amino acid residues, obtained by N-terminal amino acid sequence analysis, matched to polypeptide sequences deduced from cDNA sequences of the cryptophyte Guillardia theta. The term "ejectisins" is introduced for the 6-kDa polypeptides which represent a major component of cryptophycean ejectisomes.

Isolation, purification and some ultrastructural details of discharged ejectisomes of cryptophytes

The first successful isolation of discharged ejectisomes from pigmented cryptophytes is reported. Discharged ejectisomes from a Chroomonas and two Cryptomonas species were characterized by transmission electron microscopy using negative staining and freeze-etching. Tubular-shaped fragments of variable lengths and diameters were obtained which showed a paracrystalline lattice. Particle periodicities of 4.1 nm along the longitudinal axis and 3.1 nm in the transverse direction were measured in negative-stained fragments. The dimensions measured from freeze-etched ejectisome fragments were about 0.5-1 nm larger. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed a protein banding pattern, dominated by polypeptides of 40-44, 23-25 and 16-18 kDa. The results are discussed in the context of what is currently known about extrusomes of protists.

Multiple Independent Losses of Photosynthesis and Differing EvolutionaryRates in the Genus Cryptomonas (Cryptophyceae): Combined Phylogenetic Analyses of DNA Sequences of the Nuclear and the Nucleomorph Ribosomal Operons

In this study, evidence for at least three independent losses of photosynthesis in the freshwater cryptophyte genus Cryptomonas is presented. The phylogeny of the genus was inferred by molecular phylogenetic analyses of the nuclear internal transcribed spacer 2 (nuclear ITS2), partial nuclear large subunit ribosomal DNA (LSU rDNA), and nucleomorph small subunit ribosomal DNA (SSU rDNA, NM). Both concatenated and single data sets were used. In all data sets, the colorless Cryptomonas strains formed three different lineages, always supported by high bootstrap values (maximum parsimony, neighbor joining and maximum likelihood) and posterior probabilities (Bayesian analyses). The three leukoplast-bearing lineages displayed differing degrees of accelerated evolutionary rates in nuclear and nucleomorph rDNA. Also an increase in A + T-content in highly variable regions of the nucleomorph SSU rDNA was observed in one of the leukoplast-bearing lineages.

Extrusomes in Ciliates: Diversification, Distribution, and Phylogenetic Implications

Exocytosis is, in all likelihood, an important communication method among microbes. Ciliates are highly differentiated and specialized micro-organisms for which versatile and/or sophisticated exocytotic organelles may represent important adaptive tools. Thus, in ciliates, we find a broad range of different extrusomes, i.e ejectable membrane-bound organelles. Structurally simple extrusomes, like mucocysts and cortical granules, are widespread in different taxa within the phylum. They play the roles in each case required for the ecological needs of the organisms. Then, we find a number of more elaborate extrusomes, whose distribution within the phylum is more limited, and in some way related to phylogenetic affinities. Herein we provide a survey of literature and our data on selected extrusomes in ciliates. Their morphology, distribution, and possible function are discussed. The possible phylogenetic implications of their diversity are considered.

R-body-producing bacteria

Until 10 years ago, R bodies were known only as diagnostic features by which endosymbionts of paramecia were identified as kappa particles. They were thought to be limited to the cytoplasm of two species in the Paramecium aurelia species complex. Now, R bodies have been found in free-living bacteria and other Paramecium species. The organisms now known to form R bodies include the cytoplasmic kappa endosymbionts of P. biaurelia and P. tetraurelia, the macronuclear kappa endosymbionts of P. caudatum, Pseudomonas avenae (a free-living plant pathogen), Pseudomonas taeniospiralis (a hydrogen-oxidizing soil microorganism), Rhodospirillum centenum (a photosynthetic bacterium), and a soil bacterium, EPS-5028, which is probably a pseudomonad. R bodies themselves fall into five distinct groups, distinguished by size, the morphology of the R-body ribbons, and the unrolling behavior of wound R bodies. In recent years, the inherent difficulties in studying the organization and assembly of R bodies by the obligate endosymbiont kappa, have been alleviated by cloning and expressing genetic determinants for these R bodies (type 51) in Escherichia coli. Type 51 R-body synthesis requires three low-molecular-mass polypeptides. One of these is modified posttranslationally, giving rise to 12 polypeptide species, which are the major structural subunits of the R body. R bodies are encoded in kappa species by extrachromosomal elements. Type 51 R bodies, produced in Caedibacter taeniospiralis, are encoded by a plasmid, whereas bacteriophage genomes probably control R-body synthesis in other kappa species. However, there is no evidence that either bacteriophages or plasmids are present in P. avenae or P. taeniospiralis. No sequence homology was detected between type 51 R-body-encoding DNA and DNA from any R-body-producing species, except C. varicaedens 1038. The evolutionary relatedness of different types of R bodies remains unknown.