Himasthla elongata: Effect of infection on expression of the LUSTR-like receptor mRNA in common periwinkle haemocytes

The first mollusc mRNA coding G-protein-coupled transmembrane receptor (GPСR), homologous to human receptors LUSTR 1 (GPR107) and LUSTR 2 (GPR108), was isolated from haemocytes of common periwinkle Littorina littorea. The analyses showed that the full-length cDNA is 1935 bp long and is predicted to encode a 614 amino acid protein (named Lit-LUSTR) with a calculated molecular mass of 69.6 kDa and theoretical isoelectric point 7.59. Pair-wise comparisons between Lit-LUSTR and LUSTR proteins from human or mouse have approximately 38% identity and 56% similarity. Lit-LUSTR clusters with LUSTR-A sub-family proteins and is a first characterization of proteins containing Lung7TM-R domain in Mollusca. Significant differences were found between the Lit-LUSTR mRNA levels in haemocytes of healthy periwinkles and those naturally infected with the echinostome trematode Himasthla elongata. Down regulated expression of the LUSTR-like receptor caused by infection illustrates modification of the haemocyte receptor system and may be attributed to the previously demonstrated greater numbers of “immature” haemocytes in the circulation of infected snails.     

Rediae of echinostomatid and heterophyid trematodes suppress phagocytosis of haemocytes in Littorina littorea (Gastropoda: Prosobranchia)

A modulation of the phagocytic activity of hemocytes from the common periwinkle Littorina littorea by secretory-excretory products (SEP) released by trematode rediae during axenic in vitro cultivation was studied. The SEP released by the parasites Himasthla elongata (Echinostomatidae) and Cryptocotyle lingua (Heterophyidae) were found to inhibit the phagocytosis of zymozan particles by periwinkle hemocytes. The specificity of SEP effects was assessed: SEP of Himasthla militaris and Cryptocotyle concavum, two trematodes belonging to the same genera but infecting another closely related prosobranch snail Hydrobia ulvae, were also shown to be able to suppress L. littorea hemocytes phagocytic activity. However, no decrease in phagocytosis rate was observed when SEP of H. elongata and C. lingua were applied to monolayers of hemocytes from the bivalve mollusc Mytilus edulis. SEP from H. elongata was fractionated; only those fractions containing proteins of molecular weight more than 50 kDa were shown to possess inhibitory activity. Different H. elongata SEP concentrations were tested in for their ability to suppress phagocytosis by L. littorea hemocytes. Even very low SEP concentrations were shown to retain their ability to decrease phagocytosis rate, the inhibitory effect being dose-dependent. Hemocytes derived from snails naturally infected with H. elongata were also found to have lower phagocytic ability as compared to healthy individuals.     

A distinct type of cyclin D, CYCD4;2, involved in the activation of cell division in Arabidopsis

The Arabidopsis genome encodes 10 D-type cyclins (CYCD); however, their differential role in cell cycle control is not well known. Among them, CYCD4;2 is unique in the amino acid sequence; namely, it lacks the Rb-binding motif and the PEST sequence that are conserved in CYCDs. Here, we have shown that CYCD4;2 suppressed G1 cyclin mutations in yeast and formed a kinase complex with CDKA;1, an ortholog of yeast Cdc28, in insect cells. Hypocotyl explants of CYCD4;2 over-expressing plants showed faster induction of calli than wild-type explants on a medium containing lower concentration of auxin. These results suggest that CYCD4;2 has a promotive function in cell division by interacting with CDKA;1 regardless of the unusual primary sequence.     

Premature refutation of a human-mediated marine species introduction: the case history of the marine snail <Emphasis Type="Italic">Littorina littorea</Emphasis> in the northwestern Atlantic

The European periwinkle snail, Littorina littorea was discovered in Pictou, NS, Canada in 1840. This snail’s subsequent rapid, conspicuous spread south from Pictou along the Canadian maritime coast and then along the New England and mid-Atlantic coast to New Jersey, its virtual absence in pre-European contact deposits, and its close association with human mechanisms of transport from Europe are among the clearest evidence for a human-mediated introduction. However, molecular genetic data have been proposed as evidence that L. littorea’s occurrence in North America was not the result of a human introduction by Wares et al. (Ecol Lett 5:577–584, 2002). Reexamination of these genetic data and reexamination of all other data available reveal that a human-mediated introduction of L. littorea is the simplest explanation of its occurrence in North America. The refutation of the human-mediated introduction of L. littorea was premature.     

Premature refutation of a human-mediated marine species introduction: the case history of the marine snail <Emphasis Type="Italic">Littorina littorea</Emphasis> in the Northwestern Atlantic

The closely documented spread of the European periwinkle snail, Littorina littorea from Pictou, Nova Scotia in 1840 to New Jersey by 1870, its near absence in pre-European fossil deposits, and its close association with human mechanisms of transport from Europe, are among the clearest evidence of a human-mediated marine introduction ever reported. Genetic data were recently proposed as evidence that North American L. littorea predate European contact and thus, are not introduced. Review of these genetic data and all other data reveals that the simplest explanation of the modern occurrence of this snail in North America is by human introduction.     

Apoptosis related protein 3, an ATRA-upregulated membrane protein arrests the cell cycle at G1/S phase by decreasing the expression of cyclin D1

Human Apr3 was first cloned from HL-60 cells treated by ATRA. In this study, we further demonstrated that Apr3 could be obviously upregulated by ATRA in many other ATRA sensitive cells, suggesting a common role of Apr3 in ATRA effects. Indirect immunofluorescence assay indicates that Apr3 is a membrane protein, while its truncated form without the predicted transmembrane and intracellular domain, was likely a secreted one. Furthermore, FACS analysis showed that Apr3 overexpression could cause an obvious G1/S phase arrest which might be induced by dramatic reduction of cyclin D1 expression. Strikingly, the truncated Apr3 antagonized the negative role of Apr3 on cell cycle and cyclin D1. Taken together, our data suggest that Apr3 should play an important role in ATRA signal pathway and the predicted transmembrane and/or the intracellular domain mediates Apr3 membrane localization and is vital for the negative regulation on cell cycle and cyclin D1.     

Fine structure of the cephalic sensory organ in veliger larvae of Littorina littorea, (L.) (Mesogastropoda,Littorinidae)

The cephalic sensory organ (CSO) in planktonic veliger larvae of Littorina littorea is situated dorsally between the velar lobes at the level of the shell aperture. It consists of ciliated primary sensory cells, adjacent accessory cells and supporting epithelial cells. Cell bodies of the ciliated cells originate in the cerebral commissure and their dendrites pass to the epidermis. The flask-shaped sensory cells are characterized by a deep invaginated lumen with modified cilia arising from the cell surface in the lumen. These cilia are presumed to be non-motile because they lack striated rootlets and show a modified microtubular pattern (6 + 2, 7 + 2 and 8 + 2). The adjacent accessory cells never possess an invaginated lumen; occasionally cilia and branched microvilli arise from the apical surface. These cells may be sensory, but there is no obvious direct connection with the nervous system. The supporting epithelial cells are part of the epidermis and flank the apical necks of the sensory and accessory cells. Morphological evidence suggests that the CSO may function in chemoreception related to substrate selection at settlement, feeding or other behaviour.     

Fungal pathogen-induced changes in the antioxidant systems of leaf peroxisomes from infected tomato plants

Peroxisomes, being one of the main organelles where reactive oxygen species (ROS) are both generated and detoxified, have been suggested to be instrumental in redox-mediated plant cell defence against oxidative stress. We studied the involvement of tomato (Lycopersicon esculentum Mill.) leaf peroxisomes in defence response to oxidative stress generated upon Botrytis cinerea Pers. infection. The peroxisomal antioxidant potential expressed as superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6) and glutathione peroxidase (GSH-Px, EC 1.11.1.19) as well as the ascorbate-glutathione (AA-GSH) cycle activities was monitored. The initial infection-induced increase in SOD, CAT and GSH-Px indicating antioxidant defence activation was followed by a progressive inhibition concomitant with disease symptom development. Likewise, the activities of AA-GSH cycle enzymes: ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1) and glutathione reductase (GR, EC 1.6.4.2) as well as ascorbate and glutathione concentrations and redox ratios were significantly decreased. However, the rate and timing of these events differed. Our results indicate that B. cinerea triggers significant changes in the peroxisomal antioxidant system leading to a collapse of the protective mechanism at advanced stage of infection. These changes appear to be partly the effect of pathogen-promoted leaf senescence.     

Spatio-temporal variation in energy content of the periwinkle Littorina littorea, along a pollution gradient in the western Scheldt estuary, The Netherlands

Energy reserves, expressed as lipid, glycogen and protein fractions, were measured in the periwinkle L. littorea after 4 weeks of translocation from a relatively clean, marine (i.e. Westkapelle) to an intermediate (i.e. Ellewoutsdijk) and a highly heavy metal polluted, brackish site (i.e. Hansweert) in the Western Scheldt estuary (The Netherlands). Energy reserves of resident periwinkles from all three sites were assessed over time as well (i.e. 16/03/05, 23/03/05, 30/03/05, 13/04/05 and 11/05/05). None of the energy fractions reflected the upstream decreasing salinity and increasing heavy metal gradients. Glycogen and protein fractions decreased significantly in the translocated specimens, despite no differences were detected among the resident populations, suggesting adaptation and/or acclimation effects at the upstream parts of the estuary. The temporal data revealed a consistent post-winter, pre-spawning increase of glycogen and protein levels and a subsequent drop after spawning. Compared to glycogen and proteins, lipids follow a slightly different pattern, which may be explained by sex related and site specific interactions between biotic and abiotic factors.     

Parsimony dictates a human introduction: on the use of genetic and other data to distinguish between the natural and human-mediated invasion of the European snail Littorina littorea in North America

Two centuries of historical, archaeological, paleontological, geological, oceanographical and biological data conclusively indicate that the periwinkle snail Littorina littorea was introduced to North America from Europe either by Norse explorers 1000 years ago or by European colonists after 1840. Available genetic data do not indicate ancient divergence of North American and European L. littorea and thus do not challenge all other evidence that it was introduced from Europe by humans.     

Role of symbiotic and non-symbiotic bacteria in carbon dioxide production from hosts infected with Steinernema riobrave

Entomopathogenic nematodes of the family Steinernematidae and their mutualistic bacteria (Xenorhabdus spp.) are lethal endoparasites of insects. We hypothesized that growth of the nematode’s mutualistic bacteria in the insect host may contribute to the production of cues used by the infective juveniles (IJs) in responding to potential hosts for infection. Specifically, we tested if patterns of bacterial growth could explain differences in CO₂ production over the course of host infection. Growth of Xenorhabdus cabanillasii isolated from Steinernema riobrave exhibited the characteristic exponential and stationary growth phases. Other non-nematode symbiotic bacteria were also found in infected hosts and exhibited similar growth patterns to X. cabanillasii. Galleria mellonella larvae infected with S. riobrave produced two distinct peaks of CO₂ occurring at 25.6–36 h and 105–161 h post-infection, whereas larvae injected with X. cabanillasii alone showed only one peak of CO₂, occurring at 22.8–36.2 h post-injection. Tenebrio molitor larvae infected with S. riobrave or injected with bacteria alone exhibited only one peak of CO₂ production, which occurred later during S. riobrave infection (41.4–64.4 h post-infection compared to 20.4–35.9 h post-injection). These results indicate a relationship between bacterial growth and the first peak of CO₂ in both host species, but not for the second peak exhibited in G. mellonella.     

Changes in the rate of synthesis of wall polysaccharides during the cell cycle of yeast

Reevaluation and comparison of seemingly contradictory literature data on the mode of synthesis of wall polysaccharides during the cell cycle ofSaccharomyces cerevisiae explained the source of discrepancies and demonstrated their general consonance in the following points: 1. The rate of synthesis of glucan and mannan is not constant and does not increase continuously throughout the entire cell cycle. 2. The rate of synthesis of both polysaccharides is considerably reduced at the time of cell division and in the prebudding phase.     

Changes in the reproductive biology of Biomphalaria glabrata experimentally infected with the nematode Angiostrongylus cantonensis

This study showed for the first time changes in the reproductive biology of Biomphalaria glabrata experimentally infected with Angiostrongylus cantonensis. The values of all the parameters analyzed (total number of eggs, number of egg masses, number of eggs/mass, number of eggs/snail, percentage of viable eggs and galactogen content in albumen gland) changed with progressive infection. The results indicate the occurrence of partial parasitic castration of B. glabrata by A. cantonensis larvae, probably in response to the depletion of energy reserves, with no injuries to the gonadal tissues.     

Growth kinetics of the Golgi apparatus during the cell cycle in onion root meristems

In onion root meristems, the number of dictyosomes per cell shows a kinetics of growth strongly related to the cell cycle. During the interphase of steady-state proliferative cells, the volume density and numerical density of the Golgi apparatus decrease to reach minimum values in late-interphase cells, characterized by their greatest length. This pattern is also found in the total volume occupied by Golgi apparatus. Once in mitosis, the above-mentioned parameters begin to increase reaching maximum mean values in telophase. After the experimental uncoupling of chromosome and growth cycles by presynchronization with hydroxyurea, we found a similar behaviour pattern in the Golgi apparatus: decreasing values during interphase and a triggering of Golgi-apparatus growth in prophase independently of the bigger cell sizes reached in mitosis as an effect of pretreatment with hydroxyurea. These results indicate a cyclic kinetics of this subcellular component in higher-plant meristems, coupled with early mitotic events.     

The <Emphasis Type="Italic">transformer2</Emphasis> gene in <Emphasis Type="Italic">Musca domestica</Emphasis> is required for selecting and maintaining the female pathway of development

We present the isolation and functional analysis of a transformer2 homologue Mdtra2 in the housefly Musca domestica. Compromising the activity of this gene by injecting dsRNA into embryos causes complete sex reversal of genotypically female individuals into fertile males, revealing an essential function of Mdtra2 in female development of the housefly. Mdtra2 is required for female-specific splicing of Musca doublesex (Mddsx) which structurally and functionally corresponds to Drosophila dsx, the bottom-most regulator in the sex-determining pathway. Since Mdtra2 is expressed in males and females, we propose that Mdtra2 serves as an essential co-factor of F, the key sex-determining switch upstream of Mddsx. We also provide evidence that Mdtra2 acts upstream as a positive regulator of F supporting genetic data which suggest that F relies on an autocatalytic activity to select and maintain the female path of development. We further show that repression of male courtship behavior by F requires Mdtra2. This function of F and Mdtra2 appears not to be mediated by Mddsx, suggesting that bifurcation of the pathway at this level is a conserved feature in the genetic architecture of Musca and Drosophila.Edited by D. Tautz     

The KNS1 gene of Saccharomyces cerevisiae encodes a nonessential protein kinase homologue that is distantly related to members of the CDC28/cdc2 gene family

Summary A novel protein kinase homologue (KNS1) has been identified in Saccharomyces cerevisiae. KNS1 contains an open reading frame of 720 codons. The carboxy-terminal portion of the predicted protein sequence is similar to that of many other protein kinases, exhibiting 36% identity to the cdc2 gene product of Schizosaccharomyces pombe and 34% identity to the CDC28 gene product of S. cerevisiae. Deletion mutations were constructed in the KNS1 gene. kns1 mutants grow at the same rate as wild-type cells using several different carbon sources. They mate at normal efficiencies, and they sporulate successfully. No defects were found in entry into or exit from stationary phase. Thus, the KNS1 gene is not essential for cell growth and a variety of other cellular processes in yeast.     

Histopathological lesions of molluscs in the harbour of Norderney,Lower Saxony,North Sea (Germany)

During a combined research project at several stations along the Lower Saxony coast (German North Sea) antifouling biocides were analysed in water, sediment and biota. Pathological alterations in blue mussel, Pacific oyster and periwinkle found in the harbour of Norderney and a reference station are presented here and discussed on the background of chemical analyses. The molluscan species from the reference station Borkum East flat did not show any pathological effects in central organs, except those provoked by an infestation in the gastro-intestinal tract by the copepod Mytilicola intestinalis and trematode larvae. In most animals, the metacercaria were found in the interstitial tissue without any inflammatory reaction. In a minor number of specimens, an inflammatory reaction in the mucosa and sub-mucosa of the intestine occurred in association with Mytilicola infestation. These reactions may be evoked through mechanical irritation of the gut epithelium, metabolic products of the parasites or invading bacteria. In contrast to the observed pathological changes of mussels, oysters and periwinkles in Norderney harbour were not found to be associated with parasitic infestation. The most prominent pathological alterations were observed in the digestive system and in the gonad. In the gastro-intestinal tract inflammatory reactions, atrophy and necrosis of tubules in the mid gut gland were most pronounced in spring at the beginning of the pleasure boat season in the Pacific oyster and to a minor degree in the blue mussel and the periwinkle. The latter displayed additional inflammatory and necrotic processes in the gills. Especially in the gonad, an elevated resorption rate of gametes was present in the Pacific oyster and in the periwinkle. In addition, impact of organotin compounds was reflected in an intersex index of up to 1.4 in Littorina littorea in coincidence with masculinization of the reproductive organs.