Thirteen is enough: the myosins of Dictyostelium discoideum and their light chains

BACKGROUND: Dictyostelium discoideum is one of the most famous model organisms for studying motile processes like cell movement, organelle transport, cytokinesis, and endocytosis. Members of the myosin superfamily, that move on actin filaments and power many of these tasks, are tripartite proteins consisting of a conserved catalytic domain followed by the neck region consisting of a different number of so-called IQ motifs for binding of light chains. The tails contain functional motifs that are responsible for the accomplishment of the different tasks in the cell. Unicellular organisms like yeasts contain three to five myosins while vertebrates express over 40 different myosin genes. Recently, the question has been raised how many myosins a simple multicellular organism like Dictyostelium would need to accomplish all the different motility-related tasks. RESULTS: The analysis of the Dictyostelium genome revealed thirteen myosins of which three have not been described before. The phylogenetic analysis of the motor domains of the new myosins placed Myo1F to the class-I myosins and Myo5A to the class-V myosins. The third new myosin, an orphan myosin, has been named MyoG. It contains an N-terminal extension of over 400 residues, and a tail consisting of four IQ motifs and two MyTH4/FERM (myosin tail homology 4/band 4.1, ezrin, radixin, and moesin) tandem domains that are separated by a long region containing an SH3 (src homology 3) domain. In contrast to previous analyses, an extensive comparison with 126 class-VII, class-X, class-XV, and class-XXII myosins now showed that MyoI does not group into any of these classes and should not be used as a model for class-VII myosins. The search for calmodulin related proteins revealed two further potential myosin light chains. One is a close homolog of the two EF-hand motifs containing MlcB, and the other, CBP14, phylogenetically groups to the ELC/RLC/calmodulin (essential light chain/regulatory light chain) branch of the tree. CONCLUSION: Dictyostelium contains thirteen myosins together with 6–8 MLCs (myosin light chain) to assist in a variety of actin-based processes in the cell. Although they are homologous to myosins of higher eukaryotes, the myosins of Dictyostelium should be considered with care as models for specific functions of vertebrate myosins

Identification and phylogenetic analysis of Dictyostelium discoideum kinesin proteins

BACKGROUND: Kinesins constitute a large superfamily of motor proteins in eukaryotic cells. They perform diverse tasks such as vesicle and organelle transport and chromosomal segregation in a microtubule- and ATP-dependent manner. In recent years, the genomes of a number of eukaryotic organisms have been completely sequenced. Subsequent studies revealed and classified the full set of members of the kinesin superfamily expressed by these organisms. For Dictyostelium discoideum, only five kinesin superfamily proteins (Kif's) have already been reported. RESULTS: Here, we report the identification of thirteen kinesin genes exploiting the information from the raw shotgun reads of the Dictyostelium discoideum genome project. A phylogenetic tree of 390 kinesin motor domain sequences was built, grouping the Dictyostelium kinesins into nine subfamilies. According to known cellular functions or strong homologies to kinesins of other organisms, four of the Dictyostelium kinesins are involved in organelle transport, six are implicated in cell division processes, two are predicted to perform multiple functions, and one kinesin may be the founder of a new subclass. CONCLUSION: This analysis of the Dictyostelium genome led to the identification of eight new kinesin motor proteins. According to an exhaustive phylogenetic comparison, Dictyostelium contains the same subset of kinesins that higher eukaryotes need to perform mitosis. Some of the kinesins are implicated in intracellular traffic and a small number have unpredictable functions

Drawing the tree of eukaryotic life based on the analysis of 2,269 manually annotated myosins from 328 species

The tree of eukaryotic life was reconstructed based on the analysis of 2,269 myosin motor domains from 328 organisms, confirming some accepted relationships of major taxa and resolving disputed and preliminary classifications

Treatment of chyloperitoneum after extended lymphatic dissection during duodenopancreatectomy

Summary: Background. Chyloperitoneum is a rare postoperative complication that might be caused by an interruption of chylous ducts in the mesenteric root or the cysterna chyli. Two cases of chyloperitoneum after duodenopancreatectomy are reported in the literature. Methods. We here report the third case that developed a chyloperitoneum 2 wk postoperatively when he resumed his normal diet. Results. The patient was treated conservatively with paracenteses and chyloperitoneum subsided thereafter. Conclusions. Chyloperitoneum after extended duodenopancreatectomy might be treated conservativel

Reconstructing the phylogeny of 21 completely sequenced arthropod species based on their motor proteins

<p>Abstract</p> <p>Background</p> <p>Motor proteins have extensively been studied in the past and consist of large superfamilies. They are involved in diverse processes like cell division, cellular transport, neuronal transport processes, or muscle contraction, to name a few. Vertebrates contain up to 60 myosins and about the same number of kinesins that are spread over more than a dozen distinct classes.</p> <p>Results</p> <p>Here, we present the comparative genomic analysis of the motor protein repertoire of 21 completely sequenced arthropod species using the owl limpet <it>Lottia gigantea </it>as outgroup. Arthropods contain up to 17 myosins grouped into 13 classes. The myosins are in almost all cases clear paralogs, and thus the evolution of the arthropod myosin inventory is mainly determined by gene losses. Arthropod species contain up to 29 kinesins spread over 13 classes. In contrast to the myosins, the evolution of the arthropod kinesin inventory is not only determined by gene losses but also by many subtaxon-specific and species-specific gene duplications. All arthropods contain each of the subunits of the cytoplasmic dynein/dynactin complex. Except for the dynein light chains and the p150 dynactin subunit they contain single gene copies of the other subunits. Especially the roadblock light chain repertoire is very species-specific.</p> <p>Conclusion</p> <p>All 21 completely sequenced arthropods, including the twelve sequenced <it>Drosophila </it>species, contain a species-specific set of motor proteins. The phylogenetic analysis of all genes as well as the protein repertoire placed <it>Daphnia pulex </it>closest to the root of the Arthropoda. The louse <it>Pediculus humanus corporis </it>is the closest relative to <it>Daphnia </it>followed by the group of the honeybee <it>Apis mellifera </it>and the jewel wasp <it>Nasonia vitripenni</it>s. After this group the rust-red flour beetle <it>Tribolium castaneum </it>and the silkworm <it>Bombyx mori </it>diverged very closely from the lineage leading to the <it>Drosophila </it>species.</p

diArk – a resource for eukaryotic genome research

<p>Abstract</p> <p>Background</p> <p>The number of completed eukaryotic genome sequences and cDNA projects has increased exponentially in the past few years although most of them have not been published yet. In addition, many microarray analyses yielded thousands of sequenced EST and cDNA clones. For the researcher interested in single gene analyses (from a phylogenetic, a structural biology or other perspective) it is therefore important to have up-to-date knowledge about the various resources providing primary data.</p> <p>Description</p> <p>The database is built around 3 central tables: species, sequencing projects and publications. The species table contains commonly and alternatively used scientific names, common names and the complete taxonomic information. For projects the sequence type and links to species project web-sites and species homepages are stored. All publications are linked to projects. The web-interface provides comprehensive search modules with detailed options and three different views of the selected data. We have especially focused on developing an elaborate taxonomic tree search tool that allows the user to instantaneously identify e.g. the closest relative to the organism of interest.</p> <p>Conclusion</p> <p>We have developed a database, called diArk, to store, organize, and present the most relevant information about completed genome projects and EST/cDNA data from eukaryotes. Currently, diArk provides information about 415 eukaryotes, 823 sequencing projects, and 248 publications.</p

Whole genome duplication events in plant evolution reconstructed and predicted using myosin motor proteins

Background: The evolution of land plants is characterized by whole genome duplications (WGD), which drove species diversification and evolutionary novelties. Detecting these events is especially difficult if they date back to the origin of the plant kingdom. Established methods for reconstructing WGDs include intra-and inter-genome comparisons, K-S age distribution analyses, and phylogenetic tree constructions. Results: By analysing 67 completely sequenced plant genomes 775 myosins were identified and manually assembled. Phylogenetic trees of the myosin motor domains revealed orthologous and paralogous relationships and were consistent with recent species trees. Based on the myosin inventories and the phylogenetic trees, we have identified duplications of the entire myosin motor protein family at timings consistent with 23 WGDs, that had been reported before. We also predict 6 WGDs based on further protein family duplications. Notably, the myosin data support the two recently reported WGDs in the common ancestor of all extant angiosperms. We predict single WGDs in the Manihot esculenta and Nicotiana benthamiana lineages, two WGDs for Linum usitatissimum and Phoenix dactylifera, and a triplication or two WGDs for Gossypium raimondii. Our data show another myosin duplication in the ancestor of the angiosperms that could be either the result of a single gene duplication or a remnant of a WGD. Conclusions: We have shown that the myosin inventories in angiosperms retain evidence of numerous WGDs that happened throughout plant evolution. In contrast to other protein families, many myosins are still present in extant species. They are closely related and have similar domain architectures, and their phylogenetic grouping follows the genome duplications. Because of its broad taxonomic sampling the dataset provides the basis for reliable future identification of further whole genome duplications

Molecular phylogeny of sequenced <i>Saccharomycetes</i> reveals polyphyly of the alternative yeast codon usage

The universal genetic code defines the translation of nucleotide triplets, called codons, into amino acids. In many Saccharomycetes a unique alteration of this code affects the translation of the CUG codon, which is normally translated as leucine. Most of the species encoding CUG alternatively as serine belong to the Candida genus and were grouped into a so-called CTG clade. However, the “Candida genus” is not a monophyletic group and several Candida species are known to use the standard CUG translation. The codon identity could have been changed in a single branch, the ancestor of the Candida, or to several branches independently leading to a polyphyletic alternative yeast codon usage (AYCU). In order to resolve the monophyly or polyphyly of the AYCU, we performed a phylogenomics analysis of 26 motor and cytoskeletal proteins from 60 sequenced yeast species. By investigating the CUG codon positions with respect to sequence conservation at the respective alignment positions, we were able to unambiguously assign the standard code or AYCU. Quantitative analysis of the highly conserved leucine and serine alignment positions showed that 61.1% and 17% of the CUG codons coding for leucine and serine, respectively, are at highly conserved positions, whereas only 0.6% and 2.3% of the CUG codons, respectively, are at positions conserved in the respective other amino acid. Plotting the codon usage onto the phylogenetic tree revealed the polyphyly of the AYCU with Pachysolen tannophilus and the CTG clade branching independently within a time span of 30–100 Ma

Predicting mutually exclusive spliced exons based on exon length, splice site and reading frame conservation, and exon sequence homology

<p>Abstract</p> <p>Background</p> <p>Alternative splicing of pre-mature RNA is an important process eukaryotes utilize to increase their repertoire of different protein products. Several types of different alternative splice forms exist including exon skipping, differential splicing of exons at their 3'- or 5'-end, intron retention, and mutually exclusive splicing. The latter term is used for clusters of internal exons that are spliced in a mutually exclusive manner.</p> <p>Results</p> <p>We have implemented an extension to the WebScipio software to search for mutually exclusive exons. Here, the search is based on the precondition that mutually exclusive exons encode regions of the same structural part of the protein product. This precondition provides restrictions to the search for candidate exons concerning their length, splice site conservation and reading frame preservation, and overall homology. Mutually exclusive exons that are not homologous and not of about the same length will not be found. Using the new algorithm, mutually exclusive exons in several example genes, a dynein heavy chain, a muscle myosin heavy chain, and Dscam were correctly identified. In addition, the algorithm was applied to the whole <it>Drosophila melanogaster </it>X chromosome and the results were compared to the Flybase annotation and an <it>ab initio </it>prediction. Clusters of mutually exclusive exons might be subsequent to each other and might encode dozens of exons.</p> <p>Conclusions</p> <p>This is the first implementation of an automatic search for mutually exclusive exons in eukaryotes. Exons are predicted and reconstructed in the same run providing the complete gene structure for the protein query of interest. WebScipio offers high quality gene structure figures with the clusters of mutually exclusive exons colour-coded, and several analysis tools for further manual inspection. The genome scale analysis of all genes of the <it>Drosophila melanogaster </it>X chromosome showed that WebScipio is able to find all but two of the 28 annotated mutually exclusive spliced exons and predicts 39 new candidate exons. Thus, WebScipio should be able to identify mutually exclusive spliced exons in any query sequence from any species with a very high probability. WebScipio is freely available to academics at <url>http://www.webscipio.org</url>.</p