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At least 19 recordsLinked to original sources
PubMed2001

Phylogeny of Alariaceae, Laminariaceae, and Lessoniaceae (Phaeophyceae) based on plastid-encoded RuBisCo spacer and nuclear-encoded ITS sequence comparisons.

Concatenated sequences from the plastid-encoded RuBisCo spacer and nuclear-encoded rDNA ITS region of the Alariaceae, Laminariaceae, and Lessoniaceae as currently recognized were used to determine the phylogeny of kelps (Phaeophyceae). Our analyses indicate that all taxa in the Alariaceae, Laminariaceae, and Lessoniaceae form a monophyletic lineage (the Laminariales sensu stricto). The phylogenetic analyses show that the kelps form eight well-supported clades (represented by Egregia, Laminaria, Hedophyllum, Macrocystis, Alaria, Agarum, Ecklonia, and Lessonia) that conform to the tribes of the current morphological classification system of the "advanced" kelps. Our results suggest that the kelps should be classified into eight families rather than the three that are presently used. The interrelationships among the eight lineages were, however, unresolved in the phylogenetic analyses. In all trees, Egregia diverged first and is the sister to the other kelp taxa. Our phylogenetic analyses also indicate that Kjellmaniella and Laminaria do not form a monophyletic group. Taken together, the RuBisCo spacer and rDNA ITS prove useful for understanding the evolutionary history of the advanced kelps and provide a new framework for establishing the systematics of these commercially important brown algae.

Cell Nucleus↗
PubMed2001

A comprehensive phylogeny of the Phaeophyceae based on nrDNA sequences resolves the earliest divergences.

The present study is the first comprehensive phylogeny of the class of the Phaeophyceae. For 67 species representing all orders of the class, the sequences of the 3'-end of the small and the 5'-end of the large subunit nrRNA genes were aligned and analysed. A further analysis based on sequences of the 3'-end of the small and of the complete sequences of the 28S gene of the large subunits was also performed, but for only eight taxa. In both analyses, Tribonema marinum (Xanthophyceae) was used as outgroup. The analyses showed the Dictyotales as diverging first, followed by the Sphacelariales, then the Syringodermatales. Most of the orders currently accepted were confirmed as monophyletic groups but the Laminariales and Tilopteridales remained polyphyletic. The relationships of the remaining orders to each other were not resolved with the present data set. Ascoseira, included for the first time in a molecular study, appeared as a separate lineage without any clear relationship with other algae possessing conceptacles (Splachnidium and Fucales). Algae with stellate plastids, never studied in a global context, were polyphyletic; this result is consistent with their plastid ultrastructure and is discussed in detail. As further result of the present study, the South African genus Bifurcariopsis appeared as the sister taxon of the North Atlantic genus Himanthalia, and Xiphophora appeared as the sister taxon of Hormosira rather than as a member of the Fucaceae; the taxonomic position of these genera is discussed.

DNA, Ribosomal↗
PubMed2003

Expression of the lacZ reporter gene in sporophytes of the seaweed Laminaria japonica (Phaeophyceae) by gametophyte-targeted transformation.

The seaweed Laminaria japonica (Phaeophyceae) has a two-generation life cycle consisting of haploid gametophytes and diploid sporophytes. Female and/or male gametophytes were transformed using particle bombardment and the histological LacZ assay was performed on sporophytes generated by either parthenogenesis or inbreeding. Female gametophyte-targeted transformation resulted in similar lower efficiencies in both parthenogenetic and zygotic sporophytes, and only a chimeric expression pattern was observed. Male gametophyte-targeted transformation led to a higher efficiency, with 3.5% of the zygotic sporophytes stained completely blue (all-blue), implying the integration of lacZ at the one-cell stage. Polymerase chain reaction analysis using primers specific for a lacZ-vector juncture fragment and subsequent blotting indicated the presence of the introduced gene in the sporophytes. The method reported here has a potential for seaweed transformation using spore-based bombardment followed by the developmental process.

Genes, Reporter↗
PubMed2005

Antioxidant effect of Sargassum polycystum (Phaeophyceae) against acetaminophen induced changes in hepatic mitochondrial enzymes during toxic hepatitis.

The present study was aimed to examine the protective effects of Sargassum polycystum (Phaeophyceae) alcoholic extract on changes in liver mitochondrial enzymes against acetaminophen induced toxic hepatitis in experimental rats. The levels of protein, lipid peroxide, glutathione (GSH) in mitochondrial fraction, superoxide dismutase (SOD) and catalase (CAT) were also determined. The activities of tricarboxylic acid enzymes such as isocitrate dehydrogenase (ICD), alpha-ketoglutarate dehydrogenase (alpha-KGD), succinate dehydrogenase (SD), malate dehydrogenase (MD), NADH dehydrogenase, and cytochrome-c-oxidase were determined in mitochondrial fraction. The rats intoxicated with acetaminophen showed significant elevation in the levels of lipid peroxides with decreased levels of protein, GSH, SOD, CAT and impaired tricarboxylic acid cycle enzyme activities. The prior oral administration of S. polycystum alcoholic extract showed significant diminution in the severity of toxic hepatitis in acetaminophen-induced rats by maintaining the activities of tricarboxylic acid enzymes with concomitant improvement in the hepatic mitochondrial antiperoxidative status when compared with intoxicated animals. The results obtained in the present study indicate that the protective effects of S. polycystum extract may be due to the presence of some active compounds that are inhibitory against the free radicals generated during lipid peroxidation in acetaminophen induced toxic hepatitis.

Acetaminophen↗
PubMed2002

Calcium interference with continuous biosorption of zinc by Sargassum sp. (Phaeophyceae) in tubular laboratory reactors.

The zinc biosorptive capacity of the brown seaweed Sargassum sp. (Phaeophyceae) was studied in the presence or absence of competing calcium ions, using a continuous system with tubular fixed-bed reactors. In order to detect the effect of calcium on zinc biosorption, a 130 mg/l zinc solution was used, and calcium was added at 50-340 mg/l. The potential zinc biosorptive capacity of the biomass was markedly influenced by the presence of ionic calcium. Zinc sorption decreased with increasing calcium concentrations, as expressed by zinc uptake rates. Calcium was effectively recovered only during the initial stages of the process, as expressed by the decrease in its uptake rates. Calcium uptake rates were also much higher than zinc uptake rates, indicating that calcium was preferentially recovered when compared to zinc.

Absorption↗
PubMed2000

Tandem reduction-chloroallylboration of esters: asymmetric synthesis of lamoxirene, the spermatozoid releasing and attracting pheromone of the laminariales (Phaeophyceae).

The asymmetric synthesis of all four stereoisomers of lamoxirene (cis-2-cyclohepta-2,5-dienyl-3-vinyloxirane), the spermatozoid-releasing and -attracting pheromone of the Laminariales (Phaeophyceae), is reported. Chiral ethyl cyclohepta-2,5-diene carboxylates, prepared by a divinylcyclopropane Cope rearrangement, were effectively alkylated by means of a novel tandem DIBAL-H reduction/asymmetric alpha-chloroallylboration using (Z)-gamma-chloroallyldiisopinocampheylboranes. The ensuing syn-alpha-chlorohydrins were transformed into the corresponding vinyloxiranes with DBU, providing all four isomers of the pheromone in good chemical and excellent optical yield (90-97% ee). Spermatozoid-release assays were conducted with the sympatrically growing species L. digitata, L. hyperborea, and L. saccharina and established (1'S,2R,3S)-1c as the most active isomer in all cases.

Alkylation↗
PubMed2000

Characterisation of complementary DNAs from the expressed sequence tag analysis of life cycle stages of Laminaria digitata (Phaeophyceae).

Laminariales (Phaeophyceae, Heterokonta) are characterised by a heteromorphic digenetic life cycle with a filamentous, microscopic gametophyte and a highly evolved, macroscopic sporophyte. With the ultimate goal of comparing gene expression in each life cycle stage, complementary DNA libraries were constructed from sporophytes and gametophytes of Laminaria digitata. A set of ca. 500 expressed sequence tags (EST) was generated from each life history phase, by single-run partial sequencing of randomly picked cDNA clones. Comparison of the EST deduced amino acid sequences with database protein sequences assigned a putative identity for 39% of the 412 gametophyte clones and 48% of the 493 sporophyte clones sequenced thus far. These data represent more than 152 different proteins now probably identified in L. digitata. Several of those newly identified proteins are of interest to our understanding of the molecular physiology of kelps, for example their carbon-concentrating mechanisms, cell wall biosynthesis and halogen metabolism. EST analysis also confirmed that genes with long 3'-UTRs are widespread in Laminariales and the study of 5'-UTRs allowed the identification of a Kozak consensus sequence, c(A/C)A(A/C)CAUGGc(G/T). Several potential developmentally regulated differences in gene expression are discussed.

Algal Proteins↗
PubMed2004

Destruction of maternal centrioles during fertilization of the brown alga, Scytosiphon lomentaria (Scytosiphonales, Phaeophyceae).

In brown algal fertilization, a pair of centrioles is derived from the male gamete, irrespective of the sexual reproduction pattern, i.e., isogamy, anisogamy, or oogamy. In this study, the manner in which the maternal centriole structure is destroyed in early zygotes of the isogamous brown alga Scytosiphon lomentaria was examined by electron microscopy. At fertilization, the zygote had two pairs of centrioles (flagellar basal bodies) derived from motile male and female gametes, and there was no morphological difference between the two pairs. The flagellar basal plate and the axonemal microtubules were still connected with the distal end of centrioles. Ultrastructural observations showed that the integrity of maternal-derived centrioles began to degenerate even in the 1-h-old zygote. At that time, the cylinder of triplet microtubules of the maternal centrioles became shorter from the distal end, and a section passing through the centrioles indicated that a part of the nine triplets of microtubules changed into doublet or singlet microtubules by degeneration of B and/or C tubules. In 2-h-old zygote, there was no trace of maternal centrioles ultrastructurally, and only the paternal centrioles remained. Further, reduction of centrin accompanying destruction of the maternal centrioles was examined in immunofluorescence microscopy. Centrin localized at the paternal and the maternal centrioles had the same fluorescence intensity in the early zygotes. At 4-6 h after fertilization, two spots indicating centrin localization showed different fluorescence intensity. Later, the weaker spot disappeared completely. These results showed that there is a difference in time between the destruction of the centriolar cylinders and the reduction of centrin molecules around them.

Cell Nucleus↗
PubMed1999

Influence of centriole behavior on the first spindle formation in zygotes of the brown alga Fucus distichus (Fucales, Phaeophyceae).

The influence of centrioles, derived from the sperm flagellar basal bodies, and the centrosomal material (MTOCs) on spindle formation in the brown alga Fucus distichus (oogamous) was studied by immunofluorescence microscopy using anti-centrin and anti-beta-tubulin antibodies. In contrast to a bipolar spindle, which is formed after normal fertilization, a multipolar spindle was formed in polyspermic zygote. The number of mitotic poles in polyspermic zygotes was double the number of sperm involved in fertilization. As an anti-centrin staining spot (centrioles) was located at these poles, the multipolar spindles in polyspermic zygotes were produced by the supplementary centrioles. When anucleate egg fragments were fertilized, chromosome condensation and mitosis did not occur in the sperm nucleus. Two anti-centrin staining spots could be detected, microtubules (MTs) radiated from nearby, but the mitotic spindle was never produced. When a single sperm fertilized multinucleate eggs (polygyny), abnormal spindles were also observed. In addition to two mitotic poles containing anti-centrin staining spots, extra mitotic poles without anti-centrin staining spots were also formed, and as a result multipolar spindles were formed. When karyogamy was blocked with colchicine, it became clear that the egg nucleus proceeded independently into mitosis accompanying chromosome condensation. A monoastral spindle could be frequently observed, and in rare cases a barrel-shaped spindle was formed. However, when a sperm nucleus was located near an egg nucleus, the two anti-centrin staining spots shifted to the egg nucleus from the sperm nucleus. In this case, a normal spindle was formed, the egg chromosomes arranged at the equator, and the associated MTs elongated from one pole of the egg spindle toward the sperm chromosomes which were scattered. From these results, it became clear that paternal centrioles derived from the sperm have a crucial role in spindle formation in the brown algae, such as they do during animal fertilization. However, paternal centrioles were not adequate for the functional centrosome during spindle formation. We speculated that centrosomal materials from the egg cytoplasm aggregate around the sperm centrioles and are needed for centrosomal activation.

Antibodies↗
PubMed1998

Low divergence in rDNA ITS sequences among five species of Fucus (Phaeophyceae) suggests a very recent radiation.

Sequences from the two ribosomal DNA internal transcribed spacers (ITS1 and ITS2) were compared among five species of Fucus. Based on the present taxon sampling, parsimony analysis showed that Fucus serratus is the sister-group of the remaining Fucus species when Ascophyllum nodosum was used as an outgroup. The topology of the tree was (Fucus serratus (F. lutarius (F. vesiculosus (F. spiralis + F. ceranoides)))). The extremely low variation observed suggests a very recent radiation of the genus which supports the view widely accepted that the Fucales are among the most evolutionarily advanced of the brown algae. We further note that sequence differences between Fucus and Ascophyllum were 28%: this does not rule out the utility of ITS sequences within the Fucaceae. The very low number of informative positions allows to demonstrate empirically that distance matrix methods group on the basis of symplesiomorphies.

Base Sequence↗
PubMed2005

Complete mitochondrial genomes of the three brown algae (Heterokonta: Phaeophyceae) Dictyota dichotoma, Fucus vesiculosus and Desmarestia viridis.

We report the complete mitochondrial sequences of three brown algae (Dictyota dichotoma, Fucus vesiculosus and Desmarestia viridis) belonging to three phaeophycean lineages. They have circular mapping organization and contain almost the same set of mitochondrial genes, despite their size differences (31,617, 36,392 and 39,049 bp, respectively). These include the genes for three rRNAs (23S, 16S and 5S), 25-26 tRNAs, 35 known mitochondrial proteins and 3-4 ORFs. This gene set complements two previously studied brown algal mtDNAs, Pylaiella littoralis and Laminaria digitata. Exceptions to the very similar overall organization include the displacement of orfs, tRNA genes and four protein-coding genes found at different locations in the D. dichotoma mitochondrial genome. We present a phylogenetic analysis based on ten concatenated genes (7,479 nucleotides) and 29 taxa. Stramenopiles were always monophyletic with heterotrophic species at the base. Results support both multiple primary and multiple secondary acquisitions of plastids.

Base Sequence↗
PubMed2002

Ultrastructural study on mitosis and cytokinesis in Scytosiphon lomentaria zygotes (Scytosiphonales, Phaeophyceae) by freeze-substitution.

The ultrastructure of mitosis and cytokinesis in Scytosiphon lomentaria (Lyngbye) Link zygotes was studied by freeze fixation and substitution. During mitosis, the nuclear envelope remained mostly intact. Spindle microtubules (MTs) from the centrosome passed through the gaps of the nuclear envelope and entered the nucleoplasm. In anaphase and telophase, two daughter chromosome masses were partially surrounded with endoplasmic reticulum. After telophase, the nuclear envelope was reconstructed and two daughter nuclei formed. Then, several large vacuoles occupied the space between the daughter nuclei. MTs from the centrosomes extended toward the mid-plane between two daughter nuclei, among the vacuoles. At that time, Golgi bodies near the centrosome actively produced many vesicles. Midway between the daughter nuclei, small globular vesicles and tubular cisternae accumulated. These vesicles derived from Golgi bodies were transported from the centrosome to the future division plane. Cytokinesis then proceeded by fusion of these vesicles, but not by a furrowing of the plasma membrane. After completion of the continuity with the plasma membrane, cell wall material was deposited between the plasma membranes. The tubular cisternae were still observed at the periphery of the newly formed septum. Microfilaments could not be observed by this procedure. We conclude that cytokinesis in the brown algae proceeds by fusion of Golgi vesicles and tubular cisternae, not by a furrowing of the plasma membrane.

Anaphase↗
PubMed2006

Kinetics of copper accumulation in Lessonia nigrescens (Phaeophyceae) under conditions of environmental oxidative stress.

Juvenile individuals of the brown kelp Lessonia nigrescens were exposed to a coastal environment chronically impacted by copper mine wastes and currently displaying more than 250 nM of total dissolved copper. The kinetic of copper accumulation in the intra and extracellular compartments was determined and correlated to the oxidative burst resulting from copper-mediated oxidative stress. Accumulation involved an initial adsorption onto the outer cell wall followed by a slower uptake into the cells. A linear pattern of copper uptake over time was found during the first 52 h of exposure, and a steady state was reached at 76 h. The resulting oxidative stress was found to be inefficiently attenuated, and the intracellular level of copper remained sufficiently high to determine a persistently higher than normal level of reactive oxygen species (ROS). Thus, our results strongly suggest that, in L. nigrescens, copper needs to reach an intracellular threshold before oxidative burst develops. Furthermore, it was found that the high ROS levels generated by copper accumulation within the cells persists after the oxidative burst has ceased, suggesting a limited capacity of the algal tissue to buffer the increases of ROS caused by the environmental copper levels.

Animals↗
PubMed2000

Photoinhibition of photosynthesis in Macrocystis pyrifera (Phaeophyceae), Chondrus crispus (Rhodophyceae) and Ulva lactuca (Chlorophyceae) in outdoor culture systems.

The effect of solar radiation on photosynthesis and chlorophyll fluorescence associated to photosystem II (PS II) was determined in the Phaeophyta Macrocystis pyrifera, the Rhodophyta Chondrus crispus and the Chlorophyta Ulva lactuca by oxygen evolution and pulse-amplitude-modulated (PAM) fluorescence. The algae were maintained in 1.2 m3 outdoor tanks with constant aeration and at 8, 26 and 100% incident irradiance (E(o)). All three species showed a decrease in deltaF/F'm values during solar noon compared to values in the morning and afternoon, suggesting a photoinhibition of photosynthesis. In general, photoinhibition was negatively correlated to increasing daily irradiance in all three species. Photoinhibition in C. crispus occurred in tissue incubated at 8, 26 and 100% E(o), while in M. pyrifera and U. lactuca a decrease in deltaF/F'm values was only observed in tissue incubated at 100% E(o). This suggests that species that naturally grow at greater depths might be more susceptible to excessive light when cultured in shallow waters compared to species that naturally inhabit shallower depths. In M. pyrifera, deltaF/F'm values were lower in the afternoon than those in the morning, suggesting slower repair mechanisms of the photosystem II compared to the other species. The results suggest that photoinhibition could be reduced by reducing incident irradiance to culture systems or increasing of biomass to promote self-shading. Gross oxygenic photosynthesis increased linearly at low electron transport rates after which it saturated in all three species. This suggests that chlorophyll fluorescence could be used as an indicator of the physiological status of macroalgae maintained in dense aquaculture systems.

Chlorophyll↗
PubMed2000

Maullinia ectocarpii gen. et sp. nov. (Plasmodiophorea), an intracellular parasite in Ectocarpus siliculosus (Ectocarpales, Phaeophyceae) and other filamentous brown algae.

An obligate intracellular parasite infecting Ectocarpus spp. and other filamentous marine brown algae is described. The pathogen forms an unwalled multinucleate syncytium (plasmodium) within the host cell cytoplasm and causes hypertrophy. Cruciform nuclear divisions occur during early development. Mature plasmodia become transformed into single sporangia, filling the host cell completely, and then cleave into several hundred spores. The spores are motile with two unequal, whiplash-type flagella inserted subapically and also show amoeboid movement. Upon settlement, cysts with chitinous walls are formed. Infection of host cells is accomplished by means of an adhesorium and a stachel apparatus penetrating the host cell wall, and injection of the cyst content into the host cell cytoplasm. The parasite is characterized by features specific for the plasmodiophorids and is described as a new genus and species, Maullinia ectocarpii.

Animals↗
PubMed1999

Persistent virus integration into the genome of its algal host, Ectocarpus siliculosus (Phaeophyceae).

The brown alga Ectocarpus siliculosus frequently carries an endogenous virus, E. siliculosus virus (EsV-1), the genome of which is a circular, double-stranded DNA molecule of about 320 kbp. After infection, which occurs in the unicellular spores or gametes, the virus is present latently in all somatic cells of the host. Virus multiplication is restricted to cells of the reproductive organs. It has been an open question whether the latent viral DNA occurs as a free episome or becomes integrated into the host genome. PCR studies showed that viral DNA co-migrates with high molecular mass DNA in pulsed-field gel electrophoresis, which confirms that latent viral DNA is integrated into the host genome.

DNA, Plant↗
PubMed2002

Influence of the centrosome in cytokinesis of brown algae: polyspermic zygotes of Scytosiphon lomentaria (Scytosiphonales, Phaeophyceae).

We examined the relationship between the spindle orientation and the determination site of cytokinesis in brown algal cells using polyspermic zygotes of Scytosiphon lomentaria. When two male gametes fuse with one female gamete, the zygote has two pairs of centrioles derived from male gametes and three chloroplasts from two male and one female gametes. Just before mitosis, two pairs of centrioles duplicate and migrate towards the future mitotic poles. Spindle MTs develop and three or four spindle poles are formed. In a tri-polar spindle, one pair of centrioles shifts away from the spindle, otherwise, two pairs of centrioles exist adjoining at one spindle pole. Chromosomes arrange at several equators of the spindle. As a result of these multipolar mitoses, three or four daughter nuclei developed. Subsequently, these daughter nuclei form a line along the long axis of the cell. Cell partition always takes place between daughter nuclei, perpendicular to the long axis of the cell. Three or four daughter cells are produced by cytokinesis. Some of the daughter cells after cytokinesis do not have a nucleus, but all of them always contain the centrosome and chloroplast. Therefore, the number of daughter cells always coincides with the number of centrosomes or microtubule organizing centers (MTOCs). These results show that the cytokinetic plane in the brown algae is determined by the position of centrosomes after mitosis and is not dependent on the spindle position.

Cell Division↗