Transcript levels of the eukaryotic translation initiation factor 5A gene peak at early G(1) phase of the cell cycle in the dinoflagellate Crypthecodinium cohnii. (57/633)

A cDNA encoding a eukaryotic translation initiation factor 5A (eIF-5A) homolog in heterotrophic dinoflagellate Crypthecodinium cohnii (CceIF-5A) was isolated through random sequencing of a cDNA library. The predicted amino acid sequence possesses the 12 strictly conserved amino acids around lysine 52 (equivalent to lysine 50 or 51 in other eukaryotes). A single 1.2-kb band was detected in Northern blot analysis. In synchronized C. cohnii cells, the transcript level peaked at early G(1) and decreased dramatically on the entry to S phase. Although this has not been previously reported, studies of budding yeast (Saccharomyces cerevisiae) and certain mammalian cell types suggest a role for eIF-5A in the G(1)/S transition of the eukaryotic cell cycle. Phylogenetic trees constructed with 26 other published eIF-5A sequences suggest that CceIF-5A, while falling within the eukaryotic branches, forms a lineage separate from those of the plants, animals, and archaebacteria. The posttranslational modification of eIF-5A by a transfer of a 4-aminobutyl moiety from spermidine to conserved lysine 50 or 51, forming amino acid hypusine, is the only demonstrated specific function of polyamines in cell proliferation. It has been suggested that polyamines stimulate population growth of bloom-forming dinoflagellates in the sea. We demonstrate here putrescine-stimulated cell proliferation. Furthermore, ornithine decarboxylase inhibitor D-difluoromethylornithine and the specific hypusination inhibitor N-guanyl-1,7-diaminoheptane exhibited inhibitory effects in two species of dinoflagellates. The possible links of polyamines and saxitoxin synthesis to the arginine cycle are also discussed.  (+info)

Comparison of hemolytic activities among strains of Heterocapsa circularisquama isolated in various localities in Japan. (58/633)

Heterocapsa circularisquama (Dinophyceae), a red tide dinoflagellate, is toxic to bivalve molluscs such as the pearl oyster (Pinctada fucata), but no harmful effects of this alga on fish have been observed so far. We found that 7 strains of H. circularisquama showed hemolytic activities toward rabbit erythrocytes in a cell-density dependent manner, but to quite different extents. The strains which are known to be highly toxic to bivalves tend to show stronger hemolytic activities and vice versa, suggesting that the hemolytic activity is parallel with the shellfish toxicity of H. circularisquama. Since the hemolytic assay is simple, semiquantitative, and reproducible, this assay is useful not only to search for certain toxins responsible for the shellfish toxicity of H. circularisquama but also to estimate the potential toxicity of a newly appeared strain of H. circularisquama.  (+info)

Piscinoodinium pillulare (Schaperclaus, 1954) Lom, 1981 (Dinoflagellida) infection in cultivated freshwater fish from the northeast region of Sao Paulo State, Brazil. Parasitological and pathological aspects. (59/633)

The Aquaculture Center of Unesp, Jaboticabal, SP, Brazil, received fishes for diagnosis from fish farmers reporting fish crowding at pond edges and in water inlets. Fifty-three out of 194 cases showed round to oval, immobile whitish structures, measuring up to 162 microm diameter, identified as the dinoflagellate Piscinoodinium pillulare. In 34 diagnosed cases the parasites were present in the gills, in 2 on body surface, and 9 in both. Thirty-one out of 53 were tambacu hybrids hosts; 7, Piaractus mesopotamicus; 6, Colossoma macropomum; 5, Leporinus macrocephalus; 3, Oreochromis niloticus; and 1, Prochilodus lineatus. Fish showed increased mucous production on body surface and gills, while ecchymosis in the caudal peduncle and operculum was present. The gills also showed paleness, congestion, and petechiae. Histopathology presented a great number of trophonts situated between secondary lamellae, fixed to or detached from the epithelium. Primary lamellae presented interstitial hemorrhages, severe hyperplasia of the epithelium, goblet cells, and mononuclear infiltrates. The present work is the first report of P pillulare in Brazil and emphasizes the importance of this dinoflagellate which caused significant economic losses from 1995 through 1997.  (+info)

Second- and third-hand chloroplasts in dinoflagellates: phylogeny of oxygen-evolving enhancer 1 (PsbO) protein reveals replacement of a nuclear-encoded plastid gene by that of a haptophyte tertiary endosymbiont. (60/633)

Several dinoflagellate species have plastids that more closely resemble those of an unrelated algal group, the haptophytes, suggesting these plastids have been obtained by tertiary endosymbiosis. Because both groups are photosynthetic, all of the genes for nuclear-encoded plastid proteins might be supplied by the dinoflagellate host or some of them might have been replaced by haptophyte genes. Sequences of the conserved nuclear psbO gene were obtained from the haptophyte Isochrysis galbana, the peridinin-containing dinoflagellate Heterocapsa triquetra, and the 19'hexanoyloxy-fucoxanthin-containing dinoflagellate Karenia brevis. Phylogenetic analysis of the oxygen-evolving-enhancer (PsbO) proteins confirmed that in K. brevis the original peridinin-type plastid was replaced by that of a haptophyte, an alga which had previously acquired a red algal chloroplast by secondary endosymbiosis. It showed clearly that during this tertiary symbiogenesis the original psbO gene in the dinoflagellate nucleus was replaced by a psbO gene from the haptophyte nucleus. The phylogenetic analysis also confirmed that the origin of the peridinin-type dinoflagellate plastid was indeed a red alga.  (+info)

Development of an 18S rRNA gene-targeted PCR-based diagnostic for the blue crab parasite Hematodinium sp.. (61/633)

The 18S rRNA gene from Hematodinum sp., a parasitic dinoflagellate that infects blue crabs, was amplified, cloned, and sequenced. The sequence showed a high similarity (95% at the nucleotide level) to sequences obtained from other dinoflagellate species, including both free-living and symbiotic species. Sequence similarity was much lower when compared with parasites of other marine invertebrates with similar life histories and with the 18S rRNA gene from the blue crab. Based on comparison of sequence alignments between Hematodinium, other dinoflagellate species, protozoan pathogens of oysters, and blue crab 18S rRNA gene sequences, 2 sets of PCR primers that specifically amplified fragments of the Hematodinium 18S rRNA gene were developed and tested. One of these primer sets (Hemat-F-1487 and Hemat-R-1654) amplified a 187 bp fragment that could be used routinely as a diagnostic test for the presence of Hematodinium in hemolymph from blue crabs. This fragment was consistently amplified from genomic DNA extracted from hemolymph of Hematodinium infected blue crabs. Comparison between the PCR technique and standard histological examination indicated that the PCR technique was reliable and provided 1000 times more sensitivity than the histological methods. The sensitivity of the PCR diagnostic was estimated to be one parasite cell among 300,000 crab hemocytes. Preliminary studies using the PCR diagnostic technique suggest that Hematodinium sp. is absent in crabs collected from waters with low salinity (5 to 10 ppt), but common in crabs from higher salinity environments in estuarine waters from southeastern Georgia (USA).  (+info)

Biosynthetic study of amphidinolide W. (62/633)

The biosynthetic origins of amphidinolide W (1) were investigated on the basis of (13)C-NMR data of 13C-enriched samples obtained by feeding experiments with [1-13C], [2-13C], and [1,2-13C2] sodium acetate in cultures of a strain Y-42 of the dinoflagellate Amphidinium sp. These incorporation patterns suggested that 1 was generated from a hexaketide chain, two acetate units, four isolated C1 units from C-2 of acetates, and four branched C1 units from C-2 of acetates. The acetate-incorporation patterns for C-1-C-2-(C-21) and C-8-C-18-(C-23, C-24) of 1 corresponded well to those for C-1-C-2-(C-27) and C-5-C-15-(C-28, C-29) of amphidinolide H (2) isolated from this strain.  (+info)

A new class of transcription initiation factors, intermediate between TATA box-binding proteins (TBPs) and TBP-like factors (TLFs), is present in the marine unicellular organism, the dinoflagellate Crypthecodinium cohnii. (63/633)

Dinoflagellates are marine unicellular eukaryotes that exhibit unique features including a very low level of basic proteins bound to the chromatin and the complete absence of histones and nucleosomal structure. A cDNA encoding a protein with a strong homology to the TATA box-binding proteins (TBP) has been isolated from an expressed sequence tag library of the dinoflagellate Crypthecodinium cohnii. The typical TBP repeat signature and the amino acid motives involved in TFIIA and TFIIB interactions were conserved in this new TBP-like protein. However, the four phenylalanines known to interact with the TATA box were substituted with hydrophilic residues (His(77), Arg(94), Tyr(171), Thr(188)) as has been described for TBP-like factors (TLF)/TBP-related proteins (TRP). A phylogenetic analysis showed that cTBP is intermediate between TBP and TLF/TRP protein families, and the structural similarity of cTBP with TLF was confirmed by low affinity binding to a consensus' TATA box in an equivalent manner to that usually observed for TLFs. Six 5'-upstream gene regions of dinoflagellate genes have been analyzed and neither a TATA box nor a consensus-promoting element could be found within these different sequences. Our results showed that cTBP could bind stronger to a TTTT box sequence than to the canonical TATA box, especially at high salt concentration. Same binding results were obtained with a mutated cTBP (mcTBP), in which the four phenylalanines were restored. To our knowledge, this is the first description of a TBP-like protein in a unicellular organism, which also appears as the major form of TBP present in C. cohnii.  (+info)

Are Pfiesteria species toxicogenic? Evidence against production of ichthyotoxins by Pfiesteria shumwayae. (64/633)

The estuarine genus Pfiesteria has received considerable attention since it was first identified and proposed to be the causative agent of fish kills along the mid-Atlantic coast in 1992. The presumption has been that the mechanism of fish death is by release of one or more toxins by the dinoflagellate. In this report, we challenge the notion that Pfiesteria species produce ichthyotoxins. Specifically, we show that (i) simple centrifugation, with and without ultrasonication, is sufficient to "detoxify" water of actively fish-killing cultures of Pfiesteria shumwayae, (ii) organic extracts of lyophilized cultures are not toxic to fish, (iii) degenerate primers that amplify PKS genes from several polyketide-producing dinoflagellates failed to yield a product with P. shumwayae DNA or cDNA, and (iv) degenerate primers for NRPS genes failed to amplify any NRPS genes but (unexpectedly) yielded a band (among several) that corresponded to known or putative PKSs and fatty acid synthases. We conclude that P. shumwayae is able to kill fish by means other than releasing a toxin into bulk water. Alternative explanations of the effects attributed to Pfiesteria are suggested.  (+info)