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• Poly(A) RNAs of two invertebrates were sequenced by direct RNA-sequencing. • Polyadenylation step captured two hundred times the standard amount of noncoding RNA. • Our method captured squid mitochondrial transcripts at different steps of maturation. • Dicyemid had shorter and less abundant mitochondrial RNA as we expected. • A significantly different mode of mitochondrial transcription was found in dicyemid. To identify non-protein coding as well as truncated or premature RNA sequences expressed and obtain more complete transcriptome information, we combined the MinION direct RNA-sequencing of a conventional poly(A) RNA purification method with poly(A)-tagging of the non-coding RNA (ncRNA) fraction. This approach was applied to transcriptome sequencing of the dicyemid mesozoan, Dicyema misakiense , which has minicircular mitochondrial DNA molecules where each molecule encodes a single gene, as well as the host. Using informatics analysis, we distinguished dicyemid RNAs from those of the host squid. The poly(A) RNAs were assigned to host mitochondrial genes, host nuclear protein-coding genes, Dicyema nuclear protein-coding genes, and Dicyema mitochondrial genes in the decreasing order. Our poly(A)-tailing method recovered significantly more ncRNAs from the host compared with the sequencing of poly(A) RNAs. Furthermore, our method captured various lengths of squid mitochondrial DNA (mtDNA) transcripts at different steps of maturation including a read of 3,500 bp, which covers 21% of the squid mitochondrial genome, possibly a premature host RNA product. In contrast, shorter and less abundant reads were recovered from the dicyemid mitochondrial RNAs (mtRNAs). Even the longest read was 307 bp covering only a part of a minicircle. This study revealed significantly different modes of the mitochondrial transcription between a mesozoan and the host. Our approach to perform direct RNA-sequencing combined with the poly(A)-tailing reaction can be an effective method to fully capture non-poly(A) transcripts in a wide range of organisms. [ABSTRACT FROM AUTHOR]

The upside-down jellyfish Cassiopea, like many cnidarians, form obligate symbioses with dinoflagellates belonging to the genus Symbiodinium (commonly known as zooxanthellae). In adult Cassiopea, the symbiosis is specific, with a given Cassiopea species hosting a particular symbiont phylotype throughout broad distributions. However multiple phylotypes of Symbiodinium can infect the scyphistoma (polyp) stage of development, making Cassiopea spp. an ideal model to study the effects of symbiont phylotype on host development and proliferation. To assess the flexibility of symbiont acquisition and to understand how symbiont identity affects the early stages of Cassiopea development, symbiont uptake and host developmental traits were monitored in two species of Cassiopea that were exposed to multiple symbiont phylotype in laboratory and field experiments. Scyphistomae of Cassiopea ornata and Cassiopea xamachana both demonstrated flexibility in their symbiosis at the scyphistoma stage during which they acquired a range of laboratory cultured Symbiodinium. The presence of symbionts in C. ornata increased planuloid production relative to uninfected controls, and the rate at which symbionts accumulated in the polyp tissues varied with symbiont phylotype. Laboratory infected C. xamachana polyps continued to take up novel/additional symbiont types when transferred to the field; however, novel uptake occurred significantly less frequently in polyps that harbored homologous (ITS type-A1) symbionts prior to field placement. Similarly, ephyrae of C. ornata were able to acquire additional symbiont types even when already infected with Symbiodinium ITS type C1. Our findings demonstrate that the symbiosis is flexible within the early ontogeny of Cassiopea, but that associating with the "right" symbiont may provide a developmental advantage for that host. [ABSTRACT FROM AUTHOR]

Abstract: Structures of the prokaryotic homologue of rhomboid proteases reveal a core of six transmembrane helices, with the active-site residues residing in a hydrophilic cavity. The native environment of rhomboid protease is a lipid bilayer, yet all the structures determined thus far are in a nonnative detergent environment. There remains a possibility of structural artefacts arising from the use of detergents. In an attempt to address the effect of detergents on the structure of rhomboid protease, crystals of GlpG, an Escherichia coli rhomboid protease in a lipid environment, were obtained using two alternative approaches. The structure of GlpG refined to 1. 7-Å resolution was obtained from crystals grown in the presence of lipid bicelles. This structure reveals well-ordered and partly ordered lipid molecules forming an annulus around the protein. Lipid molecules adapt to the surface features of protein and arrange such that they match the hydrophobic thickness of GlpG. Virtually identical two-dimensional crystals were also obtained after detergent removal by dialysis. A comparison of an equivalent structure determined in a completely delipidated detergent environment provides insights on how detergent substitutes for lipid. A detergent molecule is also observed close to the active site, helping to postulate a model for substrate binding and hydrolysis in rhomboids. [Copyright &y& Elsevier]

Paphia rhomboïdes is an infaunal filter-feeding bivalve, particularly widespread and abundant in the English Channel. In order to investigate the influence of the growth-related post-settlement processes on its distribution, a spatial growth model was developed and linked to an existing ecological model of the English Channel. This model was partially parameterized on the basis of a specific ecophysiological experimental study, and calibrated with growth data collected in the “Golfe Normand-Breton” (GNB), a region of the English Channel. Compared to the actual distribution of P. rhomboïdes, the results suggest a strong influence of the growth-related processes on the distribution of the species: particularly, the extremely low growth obtained with the model in the Western Channel can explain the almost complete absence of the species in this area. [Copyright &y& Elsevier]

Dicyemida are simply organized metazoans with a long axial cell surrounded by a layer of ciliated peripheral cells. Stem cells and propagates develop inside the cytoplasm of the axial cell. Two types of propagates exist, asexually formed vermiform embryos and sexually derived infusoriform larvae, neither of which, however, develop by gastrulation. Thus, Dicyemida lack all traits typical of common metazoa and represent a pre-nervous state of organization. In this study, immunofluorescence and immunoelectron microscopy have been used to investigate the presence of a serotonin-like molecule in adults and larvae of Dicyema typus and Dicyemennea antarcticensis. Generally, in the adults of both species, the main immunoreactive structures are confined either to small vesicles inside the peripheral cells or to prominent vesicles in the axial cell, the latter vesicles apparently playing a role during the differentiation of the stem cells and the development of the propagates. In all stages, faint immunoreactivity can be observed over the surface membrane and the ciliary apparatus and over the heterochromatic blocks in the nuclei. Surprisingly, in the infusoriform larva, striking immunoreactivity occurs in the vesicles of the capsule cells covering the urn cells, which contain germinal cells. These vesicles might represent stores used in a later life phase of the animal. The results suggest that, in the pre-nervous Dicyemida, serotonin in its ancestral form may function as a hormone regulating essential developmental and morphogenetic processes. [ABSTRACT FROM AUTHOR]

The Brahma (Brm) complex of Drosophila melanogaster is a SWI/SNF-related chromatin remodeling complex required to correctly maintain proper states of gene expression through ATP-dependent effects on chromatin structure. The SWI/SNF complexes are comprised of 8–11 stable components, even though the SWI2/SNF2 (BRM, BRG1, hBRM) ATPase subunit alone is partially sufficient to carry out chromatin remodeling in vitro. The remaining subunits are required for stable complex assembly and/or proper promoter targeting in vivo. Our data reveals that SNR1 (SNF5-Related-1), a highly conserved subunit of the Brm complex, is required to restrict complex activity during the development of wing vein and intervein cells, illustrating a functional requirement for SNR1 in modifying whole complex activation functions. Specifically, we found that snr1 and brm exhibited opposite mutant phenotypes in the wing and differential misregulation of genes required for vein and intervein cell development, including rhomboid, decapentaplegic, thick veins, and blistered, suggesting possible regulatory targets for the Brm complex in vivo. Our genetic results suggest a novel mechanism for SWI/SNF-mediated gene repression that relies on the function of a ‘core’ subunit to block or shield BRM (SWI2/SNF2) activity in specific cells. The SNR1-mediated repression is dependent on cooperation with histone deacetylases (HDAC) and physical associations with NET, a localized vein repressor. [Copyright &y& Elsevier]

The zebrafish nlz gene has a rostral expression limit at the presumptive rhombomere (r) 3/r4 boundary during gastrula stages, and its expression progressively expands rostrally to encompass both r3 and r2 by segmentation stages, suggesting a role for nlz in hindbrain development. We find that Nlz is a nuclear protein that associates with the corepressor Groucho, suggesting that Nlz acts to repress transcription. Consistent with a role as a repressor, misexpression of nlz causes a loss of gene expression in the rostral hindbrain, likely due to ectopic nlz acting prematurely in this domain, and this repression is accompanied by a partial expansion in the expression domains of r4-specific genes. To interfere with endogenous nlz function, we generated a form of nlz that lacks the Groucho binding site and demonstrate that this construct has a dominant negative effect. We find that interfering with endogenous Nlz function promotes the expansion of r5 and, to a lesser extent, r3 gene expression into r4, leading to a reduction in the size of r4. We conclude that Nlz is a transcriptional repressor that controls segmental gene expression in the hindbrain. Lastly, we identify additional nlz-related genes, suggesting that Nlz belongs to a family of zinc-finger proteins. [Copyright &y& Elsevier]

Several characters involved in the life cycle in dicyemids were examined to understand reproductive strategy and adaptations to cephalopod hosts. In most dicyemids distinctly small numbers of sperms are produced in a hermaphroditic gonad (infusorigen). The number of eggs and sperms are roughly equal (means of the number of sperm:egg=1:1.58). An inverse proportional relationship was found between the number of infusorigens and the gametes, suggesting a trade-off between them. Fecundity was positively correlated with the body size of adult stages (nematogens and rhombogens). Fecundity of a single dicyemid is not very high compared with that of the other endoparasite taxa, but a total reproductive capacity per community is high, because a great number of individuals multiply asexually in the renal sac. The size of mature infusoriform embryos (dispersal embryos) that develop from fertilized eggs was not correlated with their adult sizes, but the size of embryos was correlated with the maximum mantle length of the host octopus species. Although at present the process of infecting new hosts is still unknown, the size of the infusoriform embryo is likely determined by host-specific factors in this process. The size of vermiform embryos that are asexually formed from agametes was positively correlated with size of the adults; however, the number of vermiform embryos present in the axial cell of adults was not correlated with size of the adults. A correlation was not found between maximum mantle length of the host cephalopod species and length of the adult dicyemids. In dicyemid species the size of adults appears to be constrained by the renal habitat, including renal-pancreatic complex and branchial hearts of each host cephalopod species. Size thus may be determined by the volume of the renal sac, the diameter of the renal tubules, or the depth of folding in the surface of glandular renal appendages of cephalopods. [ABSTRACT FROM AUTHOR]

The renal sacs of a diversity of cephalopod molluscs were examined to study the morphology of dicyemid mesozoans. Most of the dicyemid species studied were found to be host specific. Typically, two or more species of dicyemids were present in each host species or each host individual. When dicyemid species co-occurred, their calotte shapes were distinctly different. The following variations in calotte shapes were usually detected within a given host individual: (1) when two species of dicyemids were present, two distinct calotte shapes, conical and discoidal, were observed; (2) when three species of dicyemids were present, three types of calotte configurations were observed, conical (two grades) and discoidal; (3) when more than four species of dicyemids were present, at least one species was characterized by its rare irregularly shaped calotte. As a rule, when more than two dicyemid species were present in a single host individual, calotte shapes were dissimilar. Calotte shapes in dicyemid species from different host species more closely resemble each other than those of dicyemids observed within the same host species. Dicyemids with conical or dome-shaped calottes are found within the convolutions or folds of the renal appendages, whereas those with flat, discoidal calottes attach to the surface of the renal appendages. In the dicyemids, calotte morphology seems to result from adaptation to the structure of host renal tissues and helps to facilitate niche separation of coexisting species. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined the feeding behavior and acquisition of zooxanthellae by planula larvae of the sea anemone Anthopleura elegantissima. Overview of the symbiotic associations between cnidarians and photosynthetic dinoflagellates in shallow marine environments; Materials and methods; Results of the study.

An important feature of the foci of zoonotic cutaneous leishmaniasis (ZCL) in Turkmenistan and Uzbekistan is a 6-10-month break in transmission when Leishmania parasites persist in great gerbils (Rhombomys opimus) - the main host for three species (L. major, L. turanica and L. gerbilli). Almost all (95%) of the laboratory-maintained R. opimus experimentally infected with L. major cured their infections within 6 months, a situation which, if mirrored in field conditions, cannot provide reliable persistence of the infection to the next transmission season. However, infections with L. turanica alone persisted for a mean of 15 months, and mixed infections of L. major and L. turanica persisted even longer (mean = 25 months), parasites of both species remaining detectable in the skin for at least 18 months. Isoenzyme identification of 664 isolates obtained from wild-caught R. opimus, and of 58 cloned strains developed from them, showed that L. turanica, which is non-pathogenic for humans, tends to predominate in the gerbils from all types of natural ZCL foci, including those which are hyper-endemic; in June, L. turanica may be present in 80%-100% of the R. opimus in the foci. In contrast, infections with L. major alone occur far less commonly, and are especially hard to find at the beginning of the transmission season. However, 5%-25% of great gerbils in these foci are each infected with a mixture of L. major and L. turanica. In hyper- and meso-endemic foci, the proportion of L. major within mixed infections of Leishmania increases significantly towards the end of transmission season (August-September). It would appear, therefore, that mixed L. major / L. turanica infections in R. opimus promote the persistence of L. major between transmission seasons. [ABSTRACT FROM AUTHOR]

Summary The animal groups of Orthonectida and Dicyemida are tiny, extremely simple, vermiform endoparasites of various marine animals and have been linked in the Mesozoa ( Figure 1 ). The Orthonectida ( Figures 1 A and 1B) have a few hundred cells, including a nervous system of just ten cells [ 2 ], and the Dicyemida ( Figure 1 C) are even simpler, with ∼40 cells [ 3 ]. They are classic “Problematica” [ 4 ]—the name Mesozoa suggests an evolutionary position intermediate between Protozoa and Metazoa (animals) [ 5 ] and implies that their simplicity is a primitive state, but molecular data have shown they are members of Lophotrochozoa within Bilateria [ 6–9 ], which means that they derive from a more complex ancestor. Their precise affinities remain uncertain, however, and it is disputed whether they even constitute a clade. Ascertaining their affinities is complicated by the very fast evolution observed in their genes, potentially leading to the common systematic error of long-branch attraction (LBA) [ 10 ]. Here, we use mitochondrial and nuclear gene sequence data and show that both dicyemids and orthonectids are members of the Lophotrochozoa. Carefully addressing the effects of unequal rates of evolution, we show that the Mesozoa is polyphyletic. While the precise position of dicyemids remains unresolved within Lophotrochozoa, we identify orthonectids as members of the phylum Annelida. This result reveals one of the most extreme cases of body-plan simplification in the animal kingdom; our finding makes sense of an annelid-like cuticle in orthonectids [ 2 ] and suggests that the circular muscle cells repeated along their body [ 11 ] may be segmental in origin. [ABSTRACT FROM AUTHOR]