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PubMed1993

Clinical and pathologic findings of blue-green algae (Microcystis aeruginosa) intoxication in a dog.

A healthy dog developed signs of lethargy and vomiting after ingesting water from a tide pool containing blue-green algae. Fulminant hepatic failure occurred, and the dog was euthanized 52 hours later. At necropsy, the liver was large, friable, and discolored a dark red. Histopathology showed hepatocyte dissociation, degeneration, and necrosis. The alga was identified as Microcystis aeruginosa, a known hepatotoxin. The intraperitoneal administration of lyophilized cell material from the bloom caused hepatic necrosis in mice.

Animals↗

PubMed2006

Quantitative analysis of cell-type specific gene expression in the green alga Volvox carteri.

BACKGROUND: The multicellular alga Volvox carteri possesses only two cell types: mortal, motile somatic cells and potentially immortal, immotile reproductive cells. It is therefore an attractive model system for studying how cell-autonomous cytodifferentiation is programmed within a genome. Moreover, there are ongoing genome projects both in Volvox carteri and in the closely related unicellular alga Chlamydomonas reinhardtii. However, gene sequencing is only the beginning. To identify cell-type specific expression and to determine relative expression rates, we evaluate the potential of real-time RT-PCR for quantifying gene transcript levels. RESULTS: Here we analyze a diversified pool of 39 target genes by real-time RT-PCR for each cell type. This gene pool contains previously known genes with unknown localization of cellular expression, 28 novel genes which are described in this study for the first time, and a few known, cell-type specific genes as a control. The respective gene products are, for instance, part of photosynthesis, cellular regulation, stress response, or transport processes. We provide expression data for all these genes. CONCLUSION: The results show that quantitative real-time RT-PCR is a favorable approach to analyze cell-type specific gene expression in Volvox, which can be extended to a much larger number of genes or to developmental or metabolic mutants. Our expression data also provide a basis for a detailed analysis of individual, previously unknown, cell-type specifically expressed genes.

Algal Proteins↗

PubMed2006

The complete plastid genome sequence of the parasitic green alga Helicosporidium sp. is highly reduced and structured.

BACKGROUND: Loss of photosynthesis has occurred independently in several plant and algal lineages, and represents a major metabolic shift with potential consequences for the content and structure of plastid genomes. To investigate such changes, we sequenced the complete plastid genome of the parasitic, non-photosynthetic green alga, Helicosporidium. RESULTS: The Helicosporidium plastid genome is among the smallest known (37.5 kb), and like other plastids from non-photosynthetic organisms it lacks all genes for proteins that function in photosynthesis. Its reduced size results from more than just loss of genes, however; it has little non-coding DNA, with only one intron and tiny intergenic spaces, and no inverted repeat (no duplicated genes at all). It encodes precisely the minimal complement of tRNAs needed to translate the universal genetic code, and has eliminated all redundant isoacceptors. The Helicosporidium plastid genome is also highly structured, with each half of the circular genome containing nearly all genes on one strand. Helicosporidium is known to be related to trebouxiophyte green algae, but the genome is structured and compacted in a manner more reminiscent of the non-photosynthetic plastids of apicomplexan parasites. CONCLUSION: Helicosporidium contributes significantly to our understanding of the evolution of plastid DNA because it illustrates the highly ordered reduction that occurred following the loss of a major metabolic function. The convergence of plastid genome structure in Helicosporidium and the Apicomplexa raises the interesting possibility that there are common forces that shape plastid genomes, subsequent to the loss of photosynthesis in an organism.

Chlorophyta↗

PubMed2004

Red marine alga Bryothamnion triquetrum lectin induces endothelium-dependent relaxation of the rat aorta via release of nitric oxide.

We have investigated the vascular relaxant effects of the lectin from a red marine alga Bryothamnion triquetrum (BTL), in particular, the endothelial-dependency and the participation of a specific glycoprotein-binding site. BTL (1-100 microg mL(-1)) was applied to rat isolated aortic rings, with or without endothelium, tonically precontracted with phenylephrine (0.1 microM). Endothelium-dependent relaxation was assessed in the presence of indometacin (10 microM), L-nitro arginine methyl ester (L-NAME, 100 microM) and tetraethylammonium (TEA, 500 microM). For the involvement of the glycoprotein-binding site, BTL was assayed in presence of mucin (300 microg mL(-1)) or N-acetyl D-glucosamine (GlcNAc; 300 microg mL(-1)), a specific and non-specific lectin-binding sugar, respectively. BTL fully and concentration dependently relaxed preparations that possessed an intact endothelium (IC50 (concn producing 50% contraction) = 12.1 +/- 1.6 microg mL(-1)), whereas no significant relaxation was observed in endothelial-denuded tissue. L-NAME, but not indometacin or TEA, completely inhibited the lectin relaxation, suggesting the involvement of nitric oxide (NO). The lectin in association with mucin, but not with GlcNAc, inhibited BTL-induced relaxation, implicating the involvement of the lectin binding site. Our data suggest that the relaxant effect of the red marine alga Bryothamnion triquetrumlectin on isolated aorta occurs via interaction with a specific lectin-binding site on the endothelium, resulting in a release of NO.

Animals↗

PubMed1996

The cruciated microtubule-associated fibers of the green alga Dunaliella bioculata consist of a 31 kDa SF-assemblin.

Cytoskeletons of Dunaliella bioculata, the biflagellate wallless green alga, were isolated and analyzed using a monoclonal and a polyclonal antibody raised against SF-assemblin, the major protein of the two striated microtubule-associated fibers of the alga Spermatozopsis similis. Indirect immunofluorescence showed antigenic structures associated with the four microtubular flagellar roots. SDS-PAGE followed by immunoblot analysis revealed a cross-reacting polypeptide of 31 kDa. This protein of D. bioculata was isolated using gel filtration chromatography in 8 M urea and in vitro reassembly of striated fibers. Microsequencing of the purified protein yielded various peptides, which could be aligned along the sequence of SF-assemblin from S. similis. A complete sequence of the Dunaliella protein was obtained by cDNA cloning. It documents the non helical head domain followed by a helical rod domain with a 29 residue repeat pattern based on four heptads followed by a skip residue. Compared to SF-assemblin of S. similis the SF-assemblin of Dunaliella has a shorter head and a slightly longer rod domain. The two algal SF-assemblins share only 57% sequence identity. We conclude that SF-assemblin and related proteins in various protists are representatives of a new class of alpha-helical proteins characterized by the ability to form a special segmented coiled coil and to assemble into striated fibers of 2 nm protofilaments in vivo and in vitro.

Amino Acid Sequence↗

PubMed1978

Osmoregulation in the alga Vacuolaria virescens. Structure of the contractile vacuole and the nature of its association with the Golgi apparatus.

The contractile vacuole of the chloromonadophycean alga Vacuolaria virescens is a permanent structure that possesses a specialized membrane: subunits of this membrane have a diameter of 21-24 nm and in places are arranged in a regular hexagonal pattern. The lateral walls of these subunits form regularly spaced bristles or pegs which extend inwards from the trilaminar membrane for a distance of 13-15 nm. The contractile vacuole is situated immediately above an extensive Golgi apparatus that covers most of the anterior surface of the nucleus. Vesicles of Golgi origin give rise to subsidiary vacuoles which in turn empty into the contractile vacuole. Golgi vesicles, subsidiary vacuoles and the contractile vacuole contain similar electron-dense material. It is suggested that this material might be a highly hydrophilic substance which will attract water from the cytoplasm into the Golgi vesicles, subsidiary vacuoles and contractile vacuole from whence it is discharged from the cell. This method of osmoregulation is compared to that occurring in other algae and protozoa.

Chlorophyta↗

PubMed1979

The route of entry of cytoplasmically synthesized proteins into chloroplasts of algae possessing chloroplast ER.

In 8 classes of algae, namely the Cryptophyceae, Raphidophyceae, Haptophyceae, Chrysophyceae, Bacillariophyceae, Xanthophyceae, Eustigmatophyceae and Phaeophyceae, the chloroplasts, in addition to being surrounded by a double-membraned chloroplast envelope, are also enclosed by a cisterna of endoplasmic reticulum called the chloroplast ER. Often this ER cisterna is continuous with the outher membrane of the nuclear envelope in such a manner that the nuclear envelope forms a part of the ER sac enclosing the chloroplast. In all these classes of algae except the Cryptophyceae, a regular network of tubules and vesicles, named the periplastidal reticulum, is present at a specific location between the chloroplast envelope and the chloroplast ER. In the Cryptophyceae, scattered vesicles are found between the chloroplast envelope and the chloroplast ER. Ribosomes which have been shown to be arranged to polysomes are found on the outer membrane of the chloroplast ER. It is proposed that nuclear-coded proteins which are destined for the chloroplast are synthesized on these polysomes, passing during synthesis into the lumen of the ER cisterna. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles containing these proteins then pinch off the chloroplast ER and form the periplastidal reticulum. Vesicles then fuse with the outer membrane of the chloroplast envelope thereby delivering their contents to the lumen of the chloroplast envelope. Proteins then cross the inner membrane of the chloroplast envelope in an as yet unknown manner. Experimental evidence for this hypothesis comes from studies on Ochromonas danica using chloramphenicol and spectinomycin, which inhibit protein synthesis on plastid ribosomes, and cycloheximide, which inhibits protein synthesis on cytoplasmic ribosomes. In cells of Ochromonas exposed to chloramphenicol or spectinomycin, the periplastidal reticulum proliferates markedly becoming several layers thick. Presumably this build up of periplastidal reticulum occurs because the transport of cytoplasmically synthesized plastid proteins is slowed down when protein synthesis in the chloroplast is inhibited. Conversely, when cells of Ochromonas are treated with cycloheximide, there is a reduction in the amount of periplastidal reticulum presumably because there are no cytoplasmically synthesized proteins to be transported into the chloroplast.

Biological Transport↗

PubMed1980

Flagellar roots, mating structure and gametic fusion in the green alga Ulva lactuca (Ulvales).

The slightly anisogamous gametes of Ulva lactuca exhibit a cruciate flagellar root system consisting of 4 microtubular roots (4-2-4-2 system) and an elaborate system of fibrous roots associated with the 2-stranded microtubular roots. Two fibres (32-nm striation periodicity; system I fibres) closely underlie each of the 2-stranded roots, while different fibres (150-nm striation periodicity; system II fibres) run parallel to the root microtubules, and are 150-200 nm more internally located. Female gametes have 4 system II fibres, 3 of which are combined into a compound fibre associated with one microtubular root, while the fourth fibre is associated with the opposite root. In male gametes only 2 system II fibres are present, each underlying one of the two 2-stranded roots. A special region of the plasmalemma of both gamete types about 0.5 mum away from the basal bodies and located between 2 adjacent microtubular roots is structurally specialized and acts as a mating structure in gametic fusion. The region is oval-shaped and up to I.I mum long with a maximum diameter of 0.7 mum. A continuous electron-dense boundary layer underlies the plasmalemma at the edges of the mating structure. In both gamete types the mating structure consists of a fuzzy layer of material underlying the plasmalemma and special granules (60 nm diameter) are associated with this layer on its cytoplasmic side. In addition diffuse material overlies the mating structure, especially in male gametes. The mating structure is connected to 3 different kinds of flagellar roots: the boundary layer is linked to a 2-stranded microtubular root and its associated system I fibre; the fuzzy layer of the mating structure is connected with a system II fibre; and in female gametes this is the compound system II fibre. The ultrastructural changes which occur after mixing the 2 gamete types have been followed. Mating structure activation involves contraction of system II fibres (change of striation periodicity to 100 nm), detachment of special granules from the fuzzy layer of the mating structure and their replacement by electron-transparent vesicles at the prospective cell fusion site. Furthermore, release of electron-dense contents from Golgi-derived vesicles in the anterior part of both gamete types precedes cell fusion. Cell fusion is exclusively initiated in a region delimited by the 2 mating structures. After partial dissolution the 2 plasma membranes unite within the mating structure regions. The ultrastructure of gametic fusion in Ulva lactuca is compared to that of other green algae and the significance of flagellar roots in the mating process of green algae is discussed.

Chlorophyta↗

PubMed1983

Endocytosis of the symbiotic dinoflagellate Symbiodinium microadriaticum Freudenthal by endodermal cells of the scyphistomae of Cassiopeia xamachana and resistance of the algae to host digestion.

The ingestion and fate of four types of particles by endodermal cells of the scyphistomae of Cassiopeia xamachana were investigated by scanning and transmission electron microscopy. Ferritin was endocytosed pinocytotically by invagination of the plasmalemma. These small pinocytotic vesicles fuse with other similar vesicles to form larger ferritin-containing vacuoles, which eventually fuse with lysosomes. Such secondary lysosomes exhibit acid phosphatase activity. The co-occurrence of acid phosphatase activity and ferritin in secondary lysosomes achieved maximum frequency within 2 h of uptake of ferritin and was evident for at least 4 h following uptake. Artemia particles, live freshly isolated symbiotic algae (Symbiodinium microadriaticum), and heat-killed S. microadriaticum are phagocytosed by endodermal cells. Ferritin-labelled lysosomes fused with food vacuoles containing particles of Artemia. Vacuoles containing heat-killed S. microadriaticum also showed evidence of phago-lysosome fusion. S. microadriaticum in situ (i.e. in host cells) after 3 days exposure to the photosynthetic inhibitor, 3-(3-4-dichlorophenyl)-1,1-dimethylurea, appeared degenerate, and were found in loose-fitting host vacuoles, many in mid and apical portions of the host cell. More than 70% of these vacuoles with moribund algae contained the ferritin label, indicating that lysosome fusion had occurred. In contrast, live S. microadriaticum in control animals were almost always found at the base of the host cell in individual tight-fitting vacuoles with no evidence of lysosome fusion. Live S. microadriaticum apparently escape host digestion by prohibiting the fusion of lysosomes with the vacuole in which they reside. Vacuoles containing defunct algal symbionts, in contrast, were subject to lysosomal attack.

Acid Phosphatase↗

PubMed1984

A pathway of plasma membrane biogenesis bypassing the Golgi apparatus during cell division in the green alga Cylindrocapsa geminella.

Cell division in Cylindrocapsa geminella, in particular the mode of septum membrane biogenesis, has been studied with the transmission electron microscope. Septum formation takes place in a narrow layer of cytoplasm separating post-mitotic nuclei. First, each daughter nucleus develops a wide cytoplasmic pocket (invagination) containing numerous strands of rough endoplasmic reticulum (ER). Next, a proliferation of rough ER is observed in the equatorial zone of cytoplasm, which invariably contains a small number of widely scattered microtubules. The equatorially aligned cisternae of rough ER produce smooth-membraned vesicles, interpreted as smooth ER, which subsequently coalesce to form the membranous transverse septum. Thus, primary septum formation does not follow any of the two previously known basic cytokinetic patterns in green plants (i.e. plasma membrane furrowing and cell-plate formation), but instead represents a novel type of membrane flow, which effectively bypasses the Golgi apparatus. This pathway of membrane flow has remained largely ignored in current concepts of endomembrane structure and function in eukaryotes. However, it appears to be more widespread than has previously been recognized, especially in autospore-producing green algae and in red algae during the formation of tetraspores. It may represent an evolutionary intermediate type of cell division between the supposedly primitive method of plasma membrane furrowing and the more advanced cell-plate system.

Cell Division↗

PubMed1986

Three-dimensional reconstruction of the chondriome of the unicellular red alga Rhodella reticulata.

Three cells of the unicellular red alga Rhodella reticulata were serially sectioned and photographed in a transmission electron microscope in order to analyse the organization of the mitochondrial system, or chondriome, which, on the basis of cursory examination, appeared to consist of an interconnected network of one to a few organelles. The chondriome of all three cells was traced and superimposed on acetate paper and a three-dimensional model using balsa wood was constructed of one cell. The chondriome was found to consist primarily of one large, anastomosing mitochondrion located principally at the cell periphery. In addition, it appears that some cells can contain a few small mitochondria that are not connected to the main body of the chondriome. This is the first study to reveal the three-dimensional nature of the chondriome in a red alga.

Microscopy, Electron↗

PubMed1986

Regulation of intracellular algae by various strains of the symbiotic Hydra viridissima.

In observations on three strains of green hydra, the host and the algal mitotic index is closely coordinated only for the smallest. As the hydra strain size increases the coordination of host and algal mitosis progressively breaks down, first in timing for a medium-sized strain and then in rate for a large strain. Despite disparities between host and algal mitotic index, the number of algae per host cell remains constant in all strains during the interval measured. To account for this constancy we suggest that the hydra may either prolong the duration of the algal tetraspore stage or cull excess algae.

Animals↗

PubMed2003

Metabolite comparisons and the identity of nutrients translocated from symbiotic algae to an animal host.

Dinoflagellate algae of the genus Symbiodinium in symbiosis with marine animals release much of their photosynthetic carbon to the animal host. The compounds translocated to the host ('mobile compounds') were investigated by metabolite comparison as follows: a substrate was identified as a candidate mobile compound when comparable profiles of metabolites were generated from host metabolism of this substrate (supplied exogenously) and the endogenous mobile compounds. When the sea anemone Anemonia viridis was incubated with NaH14CO2 under photosynthesizing conditions, most of the radioactivity in the animal tissue was recovered from the low-molecular-mass fraction and distributed in the ratio 1:2:1 between the neutral, acidic and basic sub-fractions. Prominent 14C-labelled compounds included glucose, malate and glucose-6-phosphate. When the symbiosis was incubated with 14C-labelled glucose plus succinate or fumarate (but none of eight other substrate combinations tested), the 14C-labelled metabolites closely matched those obtained with NaH14CO2. These data suggest that glucose and succinate/fumarate (or metabolically allied compounds) may be important photosynthetic compounds transferred from the Symbiodinium cells to the tissues of A. viridis. Metabolite comparisons can be applied to study nutritional interactions in symbioses involving photosynthetic algae and, with appropriate modification, other associations between microorganisms and plants or animals.

Animals↗

PubMed2005

Tolerance of endolithic algae to elevated temperature and light in the coral Montipora monasteriata from the southern Great Barrier Reef.

Photosynthetic endolithic algae and cyanobacteria live within the skeletons of many scleractinians. Under normal conditions, less than 5% of the photosynthetically active radiation (PAR) reaches the green endolithic algae because of the absorbance of light by the endosymbiotic dinoflagellates and the carbonate skeleton. When corals bleach (loose dinoflagellate symbionts), however, the tissue of the corals become highly transparent and photosynthetic microendoliths may be exposed to high levels of both thermal and solar stress. This study explores the consequence of these combined stresses on the phototrophic endoliths inhabiting the skeleton of Montipora monasteriata, growing at Heron Island, on the southern Great Barrier Reef. Endoliths that were exposed to sun after tissue removal were by far more susceptible to thermal photoinhibition and photo-damage than endoliths under coral tissue that contained high concentrations of brown dinoflagellate symbionts. While temperature or light alone did not result in decreased photosynthetic efficiency of the endoliths, combined thermal and solar stress caused a major decrease and delayed recovery. Endoliths protected under intact tissue recovered rapidly and photoacclimated soon after exposure to elevated sea temperatures. Endoliths under naturally occurring bleached tissue of M. monasteriata colonies (bleaching event in March 2004 at Heron Island) acclimated to increased irradiance as the brown symbionts disappeared. We suggest that two major factors determine the outcome of thermal bleaching to the endolith community. The first is the microhabitat and light levels under which a coral grows, and the second is the susceptibility of the coral-dinoflagellates symbiosis to thermal stress. More resistant corals may take longer to bleach allowing endoliths time to acclimate to a new light environment. This in turn may have implications for coral survival.

Analysis of Variance↗

PubMed1994

OXYGEN TRANSPORT IN EGG MASSES OF THE AMPHIBIANS RANA SYLVATICA AND AMBYSTOMA MACULATUM: CONVECTION, DIFFUSION AND OXYGEN PRODUCTION BY ALGAE

Many amphibians lay their eggs in gelatinous masses up to 1020 cm in diameter, posing problems for diffusive oxygen delivery. Oxygen may also be provided by water convection between eggs or by oxygen production by endogenous algae. We studied egg masses of two local amphibians, Rana sylvatica and Ambystoma maculatum, to estimate the importance of each of these processes. We injected dye to check for water channels, measured oxygen partial pressures within egg masses to determine the influence of external water convection and lighting, measured oxygen consumption and production in darkness and light and calculated expected gradients through egg masses with a cylindrical, homogeneous egg mass model. Rana sylvatica had relatively loose egg masses with water channels between the eggs; water convection was important for oxygen delivery. Ambystoma maculatum had firm egg masses with no spaces in the jelly between eggs; thus, there was no opportunity for convective oxygen delivery. The egg masses were cohabited by Oophila ambystomatis, a green alga found specifically in association with amphibian egg masses. Oxygen delivery in A. maculatum was by diffusion and by local production by the algal symbiont. Analysis of a cylindrical egg mass model and measurement of oxygen gradients through egg masses indicated that diffusion alone was not adequate to deliver sufficient O2 to the innermost embryos at late developmental stages. In the light, however, egg masses had a net oxygen production and became hyperoxic. Over the course of a day with a 14 h:10 h light:dark cycle, the innermost embryos were alternately exposed to hyperoxia and near anoxia.

Journal Article↗

PubMed2001

A novel antivirally active fucan sulfate derived from an edible brown alga, Sargassum horneri.

A novel fucan sulfate (Hor-1) was isolated from the hot water extract of an edible brown alga, Sargassum horneri (Turner) C. Agardh. The fucan sulfate was revealed to have sugar linkage types, sulfate content and uronic acid content different from those of sodium hornan (Na-HOR), another fucan sulfate isolated from this alga. However, it exhibited inhibitory activity against replication of herpes simplex virus type 1 with similar potency to Na-HOR.

Antiviral Agents↗

PubMed2001

Strong induction of phytochelatin synthesis by zinc in marine green alga, Dunaliella tertiolecta.

Synthesis of phytochelatins (PCs), heavy-metal-sequestering peptides, in the marine green alga, Dunaliella tertiolecta, was evaluated under various conditions of exposure to heavy metals. To investigate the effect of heavy metals on both PC synthesis and their upstream biosynthetic reactions, an ion-pair-HPLC system was developed in this study, by which PCs and their biosynthetic intermediates, cysteine (Cys), gamma-glutamylcysteine (gammaEC) and glutathione (GSH), could be determined simultaneously with high sensitivity. When the cells were exposed to Zn2+, the level of PCs was maximal at 200 microM and significantly higher than that obtained after exposure to 400 microM Cd2+, which is the strongest inducer of PC synthesis in higher plants in vivo and in vitro as well as in microalgae. The predominant PC subtype was PC4, followed by PC3 and PC5, whereas PC2, which is generally abundant in higher plants, has the lowest level among PC2 to PC5. These results suggest that the characteristics of PC synthase in D. tertiolecta including the requirement of heavy metals for its catalysis and substrate specificity towards GSH and PC(n) are considerably different from those in higher plants and other algae. While PC synthesis proceeded in the heavy-metal-treated cells, the level of GSH did not appreciably change. To maintain the same size of the GSH pool, GSH must be newly synthesized to balance the amount consumed for PC synthesis.

Journal Article↗

PubMed1993

Activation of murine macrophages by polysaccharide fractions from marine algae (Porphyra yezoensis).

Two discrete immunomodulating fractions were obtained from marine algae (Porphyra yezoensis): one was the Porphyra water-soluble fraction (PWSF) which was extracted with hot water from the whole body of algae, and the other was the Porphyra acid-soluble fraction (PASF) which was extracted with acid from the residue. The major constituent in both PWSF and PASF was a polysaccharide, the total sugar concentration in PWSF (56.4%) being lower than that in PASF (82.2%). The high contents of 3,6-anhydrogalactose and sulfate indicated the porphyran structure in PWSF and PASF. The results of an in vitro culture assay with proteose peptone-induced macrophages from mice revealed the PWSF and PASF both enhanced glucose consumption, as well as the production of nitrite and tumor necrosis factor (TNF), but that these were increased more by PWSF than by PASF. PWSF augmented IL-I secretion from these macrophages, while PASF did not. On the other hand, the carbon clearance activity of phagocytes from mice injected intraperitoneally with PASF was higher than that from PWSF-injected mice. The injection of PASF into mice also enhanced the carbon clearance activity in a dose-dependent manner. These results suggest that the two individual fractions possessed the ability to activate macrophages in vitro and in vivo in different ways.

Animals↗