bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural variation in expression of self-incompatibility in
Arabidopsis thaliana
: Implications for the evolution of selfing
Authors: Nasrallah M. E. , Liu P. , Sherman-Broyles S. , Boggs N. A. , Nasrallah J. B.
Published: October 2004

The switch from an out-crossing to a self-fertilizing mating system is one of the most prevalent evolutionary trends in plant reproduction and is thought to have occurred repeatedly in flowering plants. However, little is known about the evolution of self-fertility and the genetic architecture of selfing. Here, we establish
Arabidopsis thaliana
as a model for genetic analysis of the switch to self-fertility in the crucifer family, where the ancestral out-crossing mode of mating is determined by self-incompatibility (SI), a genetic system controlled by the
S
locus. We show that
A. thaliana
ecotypes exhibit
S
-locus polymorphisms and differ in their ability to express the SI trait upon transformation with
S
-locus genes derived from the obligate out-crosser
Arabidopsis lyrata
. Remarkably, at least one ecotype was reverted to a stable, self-incompatible phenotype identical to that of naturally self-incompatible species. These ecotype differences are heritable and reflect the fixation in different
A. thaliana
populations of independent mutations that caused or enforced the switch to self-fertility. Their continued analysis promises to identify the loci that were the targets of natural selection for selfing and to contribute to a mechanistic understanding of the SI response.
The gut microbiota as an environmental factor that regulates fat storage
Authors: Bäckhed Fredrik , Ding Hao , Wang Ting , Hooper Lora V. , Koh Gou Young , Nagy Andras , Semenkovich Clay F. , Gordon Jeffrey I.
Published: October 2004

New therapeutic targets for noncognitive reductions in energy intake, absorption, or storage are crucial given the worldwide epidemic of obesity. The gut microbial community (microbiota) is essential for processing dietary polysaccharides. We found that conventionalization of adult germ-free (GF) C57BL/6 mice with a normal microbiota harvested from the distal intestine (cecum) of conventionally raised animals produces a 60% increase in body fat content and insulin resistance within 14 days despite reduced food intake. Studies of GF and conventionalized mice revealed that the microbiota promotes absorption of monosaccharides from the gut lumen, with resulting induction of
de novo
hepatic lipogenesis. Fasting-induced adipocyte factor (Fiaf), a member of the angiopoietin-like family of proteins, is selectively suppressed in the intestinal epithelium of normal mice by conventionalization. Analysis of GF and conventionalized, normal and
Fiaf
knockout mice established that Fiaf is a circulating lipoprotein lipase inhibitor and that its suppression is essential for the microbiota-induced deposition of triglycerides in adipocytes. Studies of
Rag1
-/- animals indicate that these host responses do not require mature lymphocytes. Our findings suggest that the gut microbiota is an important environmental factor that affects energy harvest from the diet and energy storage in the host.
Crystal structures of actin-related protein 2/3 complex with bound ATP or ADP
Authors: Nolen Brad J. , Littlefield Ryan S. , Pollard Thomas D.
Published: October 2004

Actin-related protein (Arp) 2/3 complex stimulates formation of actin filaments at the leading edge of motile cells. Nucleation of filaments depends on hydrolysis of ATP bound to Arp2. Here we report crystal structures of Arp2/3 complex with bound ATP or ADP. The nucleotides are immobilized on the face of subdomains 3 and 4 of Arp2, whereas subdomains 1 and 2 are flexible and absent from the electron density maps. This flexibility may explain why Arp2 does not hydrolyze ATP until the complex is activated. ATP stabilizes a relatively closed conformation of Arp3 with the γ-phosphate bridging loops from opposite sides of the cleft. ADP binds Arp3 in a unique conformation that favors an open cleft, revealing a conformational change that may occur in actin and Arps when ATP is hydrolyzed and phosphate dissociates. These structures provide the an opportunity to compare all nucleotide-binding states in an actin-related protein and give insights into the function of both the Arp2/3 complex and actin.
Promoter specificity in
Pseudomonas aeruginosa
quorum sensing revealed by DNA binding of purified LasR
Authors: Schuster M. , Urbanowski M. L. , Greenberg E. P.
Published: October 2004

Along with their cognate acyl-homoserine lactone signals, the quorum sensing regulators LasR and RhlR control the expression of hundreds of genes in the opportunistic human pathogen
Pseudomonas aeruginosa
. This extensive, overlapping regulatory network affords the opportunity to systematically investigate the sequence requirements and specificity determinants of large families of target promoters. Many of the
P. aeruginosa
quorum-controlled genes possess conserved palindromic promoter elements predicted to be binding sites for either one or both transcriptional regulators, but biochemical proof has not been reported. We have purified native LasR and characterized binding to various quorum-controlled promoters
in vitro
. Purified LasR was a dimer in solution that irreversibly bound two molecules of 3-oxo-C12-homoserine lactone. LasR bound several
las
-responsive promoters specifically and with high affinity, interacting cooperatively with some promoters and noncooperatively with others. LasR recognized some, but not all, of the predicted binding sites, and also bound to several unexpected sites. In contrast to predictions from genetic data, we found that the recognition sequences of
las
-specific promoters showed little overall sequence conservation and did not require dyad symmetry. We found distinct differences in sequence composition between
las
-specific noncooperative,
las
-specific cooperative, and
rhl
-responsive promoters. These results provide the basis for defining promoter specificity elements in
P. aeruginosa
quorum sensing. Insights into the molecular mechanism of LasR function have implications for the development of quorum-sensing targeted antivirulence compounds.
Inhibition of Phosphatidylserine Recognition Heightens the Immunogenicity of Irradiated Lymphoma Cells In Vivo
Authors: Bondanza Attilio , Zimmermann Valérie S. , Rovere-Querini Patrizia , Turnay Javier , Dumitriu Ingrid E. , Stach Christian M. , Voll Reinhard E. , Gaipl Udo S. , Bertling Wolf , Pöschl Ernst , Kalden Joachim R. , Manfredi Angelo A. , Herrmann Martin
Published: October 2004

Strategies to enhance the immunogenicity of tumors are urgently needed. Although vaccination with irradiated dying lymphoma cells recruits a tumor-specific immune response, its efficiency as immunogen is poor. Annexin V (AxV) binds with high affinity to phosphatidylserine on the surface of apoptotic and necrotic cells and thereby impairs their uptake by macrophages. Here, we report that AxV preferentially targets irradiated lymphoma cells to CD8+ dendritic cells for in vivo clearance, elicits the release of proinflammatory cytokines and dramatically enhances the protection elicited against the tumor. The response was endowed with both memory, because protected animals rejected living lymphoma cells after 72 d, and specificity, because vaccinated animals failed to reject unrelated neoplasms. Finally, AxV–coupled irradiated cells induced the regression of growing tumors. These data indicate that endogenous adjuvants that bind to dying tumor cells can be exploited to target tumors for immune rejection.
Siderophore Biosynthesis But Not Reductive Iron Assimilation Is Essential forAspergillus fumigatusVirulence
Authors: Schrettl Markus , Bignell Elaine , Kragl Claudia , Joechl Chistoph , Rogers Tom , Arst Herbert N. , Haynes Ken , Haas Hubertus
Published: October 2004

The ability to acquire iron in vivo is essential for most microbial pathogens. Here we show that Aspergillus fumigatus does not have specific mechanisms for the utilization of host iron sources. However, it does have functional siderophore-assisted iron mobilization and reductive iron assimilation systems, both of which are induced upon iron deprivation. Abrogation of reductive iron assimilation, by inactivation of the high affinity iron permease (FtrA), has no effect on virulence in a murine model of invasive aspergillosis. In striking contrast, A. fumigatus l-ornithine-N 5-monooxygenase (SidA), which catalyses the first committed step of hydroxamate-type siderophore biosynthesis, is absolutely essential for virulence. Thus, A. fumigatus SidA is an essential virulence attribute. Combined with the absence of a sidA ortholog—and the fungal siderophore system in general—in mammals, these data demonstrate that the siderophore biosynthetic pathway represents a promising new target for the development of antifungal therapies.
Loss of Bim Increases T Cell Production and Function in Interleukin 7 Receptor–deficient Mice
Authors: Pellegrini Marc , Bouillet Philippe , Robati Mikara , Belz Gabrielle T. , Davey Gayle M. , Strasser Andreas
Published: October 2004

Interleukin (IL)-7 receptor (R) signaling is essential for T and B lymphopoiesis by promoting proliferation, differentiation, and survival of cells. Mice lacking either IL-7 or the IL-7Rα chain have abnormally low numbers of immature as well as mature T and B lymphocytes. Transgenic expression of the apoptosis inhibitor Bcl-2 rescues T cell development and function in IL-7Rα–deficient mice, indicating that activation of a proapoptotic Bcl-2 family member causes death of immature and mature T cells. BH3-only proteins such as Bim, which are distant proapoptotic members of the Bcl-2 family, are essential initiators of programmed cell death and stress-induced apoptosis. We generated Bim/IL-7Rα double deficient mice and found that loss of Bim significantly increased thymocyte numbers, restored near normal numbers of mature T cells in the blood and spleen, and enhanced cytotoxic T cell responses to virus infection in IL-7Rα−/− mice. These results indicate that Bim cooperates with other proapoptotic proteins in the death of IL-7–deprived T cell progenitors in vivo, but is the major inducer of this pathway to apoptosis in mature T cells. This indicates that pharmacological inhibition of Bim function might be useful for boosting immune responses in immunodeficient patients.
Governments, Firms, and National Wealth: A New Pulp and Paper Industry in Postwar New Zealand
Authors: Baker Astrid
Published: October 2004

The state played an important role as political and economic manager in postwar New Zealand. By fostering manufacturing, governments aimed to provide paid, productive employment, conserve foreign exchange, and support a welfare state. The history of pulp and papermaking using state-planted pine forests is a good example of a government-business joint venture to create a new export industry and new national wealth. Governments of both major political parties cooperated in capital formation, land use, hydroelectricity, roads, railroads, a modern port, and town construction. This longterm state commitment helped propel the industry toward largescale vertical integration so that it could achieve economies of scale and scope and compete in world markets.
Radiation of the Australian flora: what can comparisons of molecular phylogenies across multiple taxa tell us about the evolution of diversity in present–day communities?
Authors: Crisp Mike , Cook Lyn , Steane Dorothy
Published: October 2004

The Australian fossil record shows that fromca. 25 Myr ago, the aseasonal–wet biome (rainforest and wet heath) gave way to the unique Australian sclerophyll biomes dominated by eucalypts, acacias and casuarinas. This transition coincided with tectonic isolation of Australia, leading to cooler, drier, more seasonal climates. From 3 Myr ago, aridification caused rapid opening of the central Australian arid zone. Molecular phylogenies with dated nodes have provided new perspectives on how these events could have affected the evolution of the Australian flora. During the Mid–Cenozoic (25–10 Myr ago) period of climatic change, there were rapid radiations in sclerophyll taxa, such asBanksia, eucalypts, pea–flowered legumes andAllocasuarina. At the same time, taxa restricted to the aseasonal–wet biome (Nothofagus, Podocarpaceae and Araucariaceae) did not radiate or were depleted by extinction. During the Pliocene aridification, two Eremean biome taxa (Lepidiumand Chenopodiaceae) radiated rapidly after dispersing into Australia from overseas. It is clear that the biomes have different histories. Lineages in the aseasonal–wet biome are species poor, with sister taxa that are species rich, either outside Australia or in the sclerophyll biomes. In conjunction with the fossil record, this indicates depletion of the Australian aseasonal–wet biome from the Mid–Cenozoic. In the sclerophyll biomes, there have been multiple exchanges between the southwest and southeast, rather than single large endemic radiations after a vicariance event. There is need for rigorous molecular phylogenetic studies so that additional questions can be addressed, such as how interactions between biomes may have driven the speciation process during radiations. New studies should include the hitherto neglected monsoonal tropics.
South American palaeobotany and the origins of neotropical rainforests
Authors: Burnham Robyn J. , Johnson Kirk R.
Published: October 2004

Extant neotropical rainforest biomes are characterized by a high diversity and abundance of angiosperm trees and vines, high proportions of entire–margined leaves, high proportions of large leaves (larger than 4500 mm2), high abundance of drip tips and a suite of characteristic dominant families: Sapotaceae, Lauraceae, Leguminosae (Fabaceae), Melastomataceae and Palmae (Arecaceae). Our aim is to define parameters of extant rainforests that will allow their recognition in the fossil record of South America and to evaluate all known South American plant fossil assemblages for first evidence and continued presence of those parameters. We ask when did these critical rainforest characters arise? When did vegetative parameters reach the level of abundance that we see in neotropical forests? Also, when do specific lineages become common in neotropical forests?

Our review indicates that evidence of neotropical rainforest is exceedingly rare and equivocal before the Palaeocene. Even in the Palaeocene, the only evidence for tropical rainforest in South America is the appearance of moderately high pollen diversity. By contrast, North American sites provide evidence that rainforest leaf physiognomy was established early in the Palaeocene. By the Eocene in South America, several lines of evidence suggest that neotropical rainforests were diverse, physiognomically recognizable as rainforest and taxonomically allied to modern neotropical rainforests. A mismatch of evidence regarding the age of origin between sites of palaeobotanical high diversity and sites of predicted tropical climates should be reconciled with intensified collecting efforts in South America. We identify several lines of promising research that will help to coalesce previously disparate approaches to the origin, longevity and maintenance of high diversity floras of South America.
Palaeobotanical studies from tropical Africa: relevance to the evolution of forest, woodland and savannah biomes
Authors: Jacobs Bonnie F.
Published: October 2004

Fossil plants provide data on climate, community composition and structure, all of which are relevant to the definition and recognition of biomes. Macrofossils reflect local vegetation, whereas pollen assemblages sample a larger area. The earliest solid evidence for angiosperm tropical rainforest in Africa is based primarily on Late Eocene to Late Oligocene (
ca
. 39–26 Myr ago) pollen assemblages from Cameroon, which are rich in forest families. Plant macrofossil assemblages from elsewhere in interior Africa for this time interval are rare, but new work at Chilga in the northwestern Ethiopian Highlands documents forest communities at 28 Myr ago. Initial results indicate botanical affinities with lowland West African forest. The earliest known woodland community in tropical Africa is dated at 46 Myr ago in northern Tanzania, as documented by leaves and fruits from lake deposits. The community around the lake was dominated by caesalpinioid legumes, but included
Acacia
, for which this, to my knowledge, is the earliest record. This community is structurally similar to modern miombo, although it is different at the generic level. The grass–dominated savannah biome began to expand in the Middle Miocene (16 Myr ago), and became widespread in the Late Miocene (
ca
. 8 Myr ago), as documented by pollen and carbon isotopes from both West and East Africa.
Metacommunity process rather than continental tectonic history better explains geographically structured phylogenies in legumes
Authors: Lavin Matt , Schrire Brian P. , Lewis Gwilym , Pennington R. Toby , Delgado–Salinas Alfonso , Thulin Mats , Hughes Colin E. , Matos Angela Beyra , Wojciechowski Martin F.
Published: October 2004

Penalized likelihood estimated ages of both densely sampled intracontinental and sparsely sampled transcontinental crown clades in the legume family show a mostly Quaternary to Neogene age distribution. The mode ages of the intracontinental crown clades range from 4–6 Myr ago, whereas those of the transcontinental crown clades range from 8–16 Myr ago. Both of these young age estimates are detected despite methodological approaches that bias results toward older ages. Hypotheses that resort to vicariance or continental history to explain continental disjunct distributions are dismissed because they require mostly Palaeogene and older tectonic events. An alternative explanation centring on dispersal that may well explain the geographical as well as the ecological phylogenetic structure of legume phylogenies is Hubbell's unified neutral theory of biodiversity and biogeography. This is the only dispersalist theory that encompasses evolutionary time and makes predictions about phylogenetic structure.
ISOLATION AND CHARACTERIZATION OF NATIVE PIGMENT‐PROTEIN COMPLEXES FROM TWO EUSTIGMATOPHYCEAE1
Authors: Arsalane Wafa , Rousseau Bernard , Thomas J. C.
Published: October 2004

Pigment‐protein complexes were isolated from two species of Eustigmatophyceae, Monodus subterraneus Peterson and Vischeria punctata Vischer, by digitonin treatment followed by density gradient centrifugation. Absorption and fluorescence spectra of the samples were monitored at various steps of preparation, and pigment composition was analyzed by reverse phase HPLC. Although the fluorescence emission spectra were very different in the two species, the absorption spectra were similar, and each exhibited an absorption band with a maximum at 487 nm attributable to violaxanthin and vaucheriaxanthin ester (the molar concentration of these pigments in Monodus was, respectively, 28 and 10 per 100 Chl a). The light‐harvesting role of these xanthophylls was ascertained by fluorescence excitation spectra. The light‐harvesting fractions (LH) collected in the upper part of the gradient were depleted in β‐carotene, whereas their xanthophyll/chlorophyll ratio was almost the same as in whole cells. This is consistent with the presence in these algae of large LH antennae and relatively small core antennae in the photosystems. In Monodus, a polypeptide of 23 kDa, immunologically related to the major LH polypeptide of brown algae, constituted the majority of the LH protein moiety.
STRUCTURE OF EXTRACELLULAR POLYSACCHARIDES PRODUCED BY A SOIL CRYPTOMONAS SP. (CRYPTOPHYCEAE)1
Authors: Paulsen Berit Smestad , Vieira Armando Augusta Henriques , Klaveness Dag
Published: October 2004

The Hindak strain of a Cryptomonas species (Cryptophyceae) produces extracellular polysaccharides. Because there is no information on the structure of these compounds in the Cryptophyceae we conducted structural studies. Gas–liquid chromatographic analyses showed that the polysaccharide is composed of fucose, rhamnose, xylose, mannose, glucose, galactose, galacturonic acid, glucuronic acid, and traces of 3‐O‐methyl galactose. The polysaccharide was separated into two subtractions by ion‐exchange chromatography. Fraction A consisted mainly of 1,3‐linked galactose units and 1,4‐linked galacturonic acid. Unlike fraction B, fraction A did not have xylose, 3‐O‐methyl galactose, or glucuronic acid. Also, its degree of branching was low compared to that of fraction B. Only traces of sulfate were present infraction A, but fraction B was 10–15% sulfated. Protein was approximately 1% in both fractions. These polysaccharides appear to be a novel type of polymer in algae.
ULTRASTRUCTURE OF THE FEEDING APPARATUS AND MYONEMAL SYSTEM OF THE HETEROTROPHIC DINOFLAGELLATE PROTOPERIDINIUM SPINULOSUM1
Authors: Jacobson Dean M. , Anderson Donald M.
Published: October 2004

The feeding veil or pallium of the thecate heterotrophic dinoflagellate Protoperidinium spinulosum Schiller is a highly vesiculate membranous sac containing several arched, sometimes bifurcated microtubular ribbons. It originates from an internal microtubular basket, passes through a sphincter‐like osmiophilic ring located inside the posterior flagellar pore, and emerges from the cell at that pore. The osmiophilic ring is part of an interconnected myonemal system (composed of two striated collars and several striated connectives) that is anchored to the pore plate and to two inward protrusions composed of minute sulcal plates. A related species, Protoperidinium punctulatum (Paulsen) Balech, also possesses a microtubular basket/osmiophilic ring complex. Elongate electron‐dense bodies within the basket resemble digestive secretory granules found in other protists. Granular, electron‐lucent microbodies clustered at the anterior end of the basket may also have a role in prey digestion. Dense membranous whorls observed within a P. spinulosum cell presented as it was preparing to initiate feeding indicate a condensed storage site for pallium membranes. A narrow microtubule‐strengthened pseudopodal appendage found in two non‐feeding cells constitutes the tow filament that serves as the initial linkage between the dinoflagellate and its food. The structures that constitute the pallium and pallium precursors, described here for the first time, are unlike those of other known protists, although some similarities with the dinoflagellate peduncle are evident. The existence of this unique system of organelles may have important ramifications in the search for evolutionary relationships among protists.
COMPARISON OF CHLOROPLAST DNA AND ALLOZYME VARIATION IN WINTER STRAINS OF THE MARINE DIATOM SKELETONEMA COSTATUM(BACILLARIOPHYTA)1
Authors: Stabile Joseph E. , Wurtzel Eleanore T. , Gallagher Jane C.
Published: October 2004

Restriction fragment length polymorphisms (RFLPs) were examined in 12 winter strains of the marine diatom Skeletonema costatum (Grev.) Cleve using homologous chloroplast gene probes. The winter strains included eight different allozyme genotypes exhibiting physiological differences. These 12 winter strains were representative of the least diverse genetic group present in Narragansett Bay populations. Five chloroplast DNA probes and four different restriction enzymes were used to analyze the 12 Narragansett Bay strains and a reference strain “Skel.” A total of 46 restriction fragments were identified. All 12 of the winter strains had identical patterns. Strain Skel exhibited two RFLPs in comparison to the Narragansett Bay strains. Calculated diversity within the winter strain group was 0.0 and 0.85 for the chloroplast DNA and allozyme data, respectively. The chloroplast DNA polymorphisms revealed by this study are expected to represent a minimum level of the chloroplast DNA diversity present in Narragansett Bay seasonal populations.
OBSERVATIONS ON THE MORPHOLOGY AND SEXUAL REPRODUCTION OFCOOLIA MONOTIS(DINOPHYCEAE)1
Authors: Maria A. Faust
Published: October 2004

The surface morphology of the dinoflagellateCoolia monotisMeunier was compared with the surface morphologyof Ostreopsis, The apical pore ofC. monotisis similar in architecture to that ofOstreopsisbut considerably longer (12 μm) than inO. heptagona(8–9 μm) andO. ovata(6–7 μm). A ventral pore inC. monotisis located on the right ventral margin between apical plate l′ and precingular plate 6″ and is similar in appearance and location to the ventral pore ofO. ovata.The longitudinal flagellum (20 μm) inC. monotisis longer than inO. ovata(12 μ). AlthoughCooliaandOstreopsisappear to be distinctly different and should remain as two separate genera, they appear to be related.

Cells ofC. monotisdivided by binary fission. Doubling time was 3–4 days in the logarithmic phase of growth at 23°C, 12:12 h L:D, 30–90 μE‐m−2·s−1, and a salinity of 36%. Cultures reached cell densities of 2.5 × 103cells·L−1after 15 days of growth.

The sexual process inC. monotisoccurred in Erdschreiber's medium when Danish soil extract was substituted with mangrove sediment extract under the culture conditions described above. Gamete fusion produced large biflagellated planozygotes (70–75 μm diam). Planozygote maturation involved cytoplasmic reorganization, loss of motility, development of a spherical shape (80–90 μm diam), and two to three orange accumulation bodies. The cells at this stage appeared to be thin‐walled cysts. Further development included reorganization of cyst contents, emergence of non‐motile gametes, and development of chloroplasts, sulcus, and girdle. The nucleus of the newly formed cells occupied 50% or more of the total cell volume. Meiosis occurred in the cyst, but nuclear cyclosis was not observed. Four daughter cells were produced within 36–48 h, and motile gametes developed. The gametes exhibited sexuality for 2 months and completed the sexual life cycle by going through a thin‐walled cyst stage.
SCALED CHRYSOPHYTES (CHRYSOPHYCEAE AND SYNUROPHYCEAE) FROM ADIRONDACK DRAINAGE LAKES AND THEIR RELATIONSHIP TO ENVIRONMENTAL VARIABLES1
Authors: Cumming Brian F. , Smol John P. , Birks H. John B.
Published: October 2004

The relationships between 23 scaled chrysophyte taxa (Chrysophyceae and Synurophyceae) and measured limnological variables in 62 Adirondack, New York, drainage lakes were examined by canonical correspondence analysis (CCA). The major proportion of variation in chrysophyte species distributions was strongly related to total monomeric Al (Alm) and Mg concentrations, and their close correlates pH, Na, Ca, and acid‐neutralizing capacity (ANC). Total monomeric Al concentrations explain a greater proportion of species variation than pH, suggesting that Alm concentrations may be more important in governing the distribution of chrysophyte taxa in these lakes. Gaussian logit (GL) and linear logit (LL) regressions of the relative percentages of individual chrysophyte taxa to lakewater pH and Alm concentrations and the examination of pH–Alm response surfaces show that many chrysophyte taxa exhibit unique responses to these environmental gradients; taxa can be characterized as alkaline, circumneutral, acidic, and pH indifferent. Within each of these groups, taxa can be characterized further based upon their optima and tolerances to Alm concentrations. Chrysophyte indicator species (i.e. a taxon with a strong statistical relationship to the environmental variable of interest, a well‐defined optimum, and a narrow tolerance to the variable of interest) for pH include Mallomonas hindonii, M. crassisquama, M. pseudocoronata, and Synura uvella; M. hindonii, M. crassisquama, M. pseudocoronata, S. petersenii, and S. spinosa are good indicators of Alm concentrations. Highly significant predictive models were developed to infer lakewater pH and Alm concentrations from the relative percentages of chrysophyte scales in the study lakes. Model evaluation was based on their correlation coefficients and the root‐mean‐squared error of prediction (RMSE) derived from bootstrapping. Weighted averaging regression and calibration with tolerance down‐weighting (i.e. weighting taxa inversely to their variance) produced superior results when compared to the computationally and data‐demanding maximum likelihood methods and to simple weighted averaging regression and calibration.
PHOTOSYNTHESIS‐IRRADIANCE RELATIONSHIPS IN PHYTOPLANKTON FROM THE PHYSICALLY STABLE WATER COLUMN OF A PERENNIALLY ICE‐COVERED LAKE (LAKE BONNEY, ANTARCTICA)1
Authors: Lizotte Michael P. , Priscu John C.
Published: October 2004

The perennially ice‐covered lakes of Antarctica have hydrodynamically stable water columns with a number of vertically distinct phytoplankton populations. We examined the photosynthesis‐irradiance characteristics of phytoplankton from four depths of Lake Bonney to determine their physiological condition relative to vertical gradients in irradiance and temperature. All populations studied showed evidence of extreme shade adaptation, including low Ik values (15–45 μE · m−2· s−1) and extremely low maximal photosynthetic rates (PBm less than 0.3 μg C ·μg chl a−1· h−1). Photosynthetic rates were controlled by temperature as well as light variations with depth. Lake Bonney has an inverted temperature profile within the trophogenic zone that increased from 0° C at the ice‐water interface to 6° C from 10 to 18 m. Deeper phytoplankton (10 m and 17 m) were found to have photosynthetic capacities (PBm) and efficiences (α) three to five times higher than those at the ice‐water interface. However, Q10 values were only ca. 2 for PBm (no temperature dependence was evident for α), suggesting that a simple temperature response cannot explain all the differences between populations. Lake Bonney phytoplankton (primarily cryptophytes and chlorophytes) had photosynthetic characteristics similar to diatoms from other physically stable environments (e.g. sea ice, benthos) and may be ecologically analogous to multiple deep chlorophyll maxima.
SEASONAL PERIODICITY OF CHRYSOPHYCEAE AND SYNUROPHYCEAE IN A SMALL NEW ENGLAND LAKE: IMPLICATIONS FOR PALEOLIMNOLOGICAL RESEARCH1
Authors: Siver Peter A. , Hamer Josephine S.
Published: October 2004

The seasonal periodicity of taxa of Chrysophyceae and Synurophyceae from a small New England lake is described for the period September 1983 through June 1988. We found 51 taxa, including 29 that accounted for over 10% of the total in at least one collection. The taxa were fitted into one of five seasonal patterns. Patterns I and II represented taxa restricted to warm (pattern I) or cold (pattern II) months, respectively. Pattern HI represented organisms that began growth in the summer, persisted through autumn and disappeared with the onset of an ice cover. Pattern IV was an extension of pattern III, in which the taxon remained in the plankton throughout the winter and disappeared soon after ice out. Species without a clear seasonal pattern were grouped as pattern V. The seasonal periodicity of the flora, as examined with ordination analyses, was found to remain remarkedly similar during the 58–month study. Except for episodes of low pH during spring snow melt and unseasonally warm or cold weather, sample scores followed a fairly consistent pattern along the first and second primary axes. Water temperature, specific conductance, and pH were important variables that controlled changes in the species composition during the course of a given year. The flora was used to develop an inference model for water temperature. According to the analyses, the remains of a surface sediment sample represented a flora that grew primarily during the late autumn period at 7.6 ° C. Ways in which seasonal data could be utilized to improve paleolimnological inference work are discussed.
SIZE HIERARCHY AND THE −3/2 “POWER LAW” RELATIONSHIP IN A COALESCENT SEAWEED1
Authors: Martínez Enrique , Santelices Bernabé
Published: October 2004

The size structure of plant populations has been characterized by two descriptors, size‐density relations and size inequality. In even aged natural or experimental populations, the logarithm of mean size is a negative function of population density, with a slope of –3/2 and a maximum intercept of 4.3. Size inequality, measured by the Gini coefficient (G.C.), ranges from maximum size homogeneity (G.C. = 0) to maximum inequality (G.C. = 1). These two descriptors have been applied mainly to land plants, and only once have they been empirically related, suggesting that the onset of self‐thinning (increase in mean size by decreasing density) reduces size inequality. We applied these descriptors and tested their empirical relations within populations of Iridaea laminarioides Bory, a red alga that, as other members of the Gigartinales and Gracilariales, exhibits coalescence of germinating spores, forming a clump of fronds with a single basal disc. Results indicate 1) lack of fit to the self‐thinning rule and transgression of the limit slope, 2) high size inequality values, 3) absence of a significant negative correlation between mean size and Gini values, 4) spatial ordering in the distribution of size inequality, with fronds decreasing in size towards the periphery of the coalescing discs, and 5) reproduction occurring mostly in the large sized fronds. In I. laminarioides transgression of the self‐thinning slope and high size inequality seems to result from spore coalescence and a growth pattern that allows the coalescing discs to grow into physiologically integrated fronds, the larger (and central) of which become reproductive. Therefore, rather than being considered exceptional, we suggest that transgression to the limit slope and high size inequality should be common among seaweeds with coalescing spores and physiological integration of individuals.
EFFECTS OF TURBULENCE ON THE MARINE DINOFLAGELLATE GYMNODINIUM NELSONII1
Authors: Berdalet Elisa
Published: October 2004

Laboratory experiments were conducted to study the effects of agitation on growth, cell division, and nucleic acid dynamics of the dinoflagellate Gymnodinium nelsonii Martin. When cultures were placed on an orbital shaker at 100 rpm, cell division was prevented, cellular volume increased up to 1.5 times that of the nonperturbed cells, the form and location of the cell nucleus were modified, and the RNA and DNA concentrations per cell increased up to 10 times those of the controls. When shaking was stopped after 10 days, cells divided immediately at about 2/3 of the division rate of the unshaken populations, and all the altered parameters were restored. If the agitation continued for more than 20 days, total cell death and disintegration occurred. Several cellular types differing in size and shape were observed in the control and shaken cultures. One possible hypothesis for these results is that failure of the cell to divide results from physical disturbance of the microtubule assemblage associated with chromosome separation during mitosis. My study suggests that small‐scale oceanic turbulence of sufficient intensity may inhibit growth of individual dinoflagellate cells, but immediate development of the population may continue when calm weather follows the active mixing period.
CYTOPLASMIC BIOSYNTHESIS OF LIGHT‐HARVESTING POLYPEPTIDES IN THE GREEN FLAGELLATE MANTONIELLA SQUAMATA (MICROMONADOPHYCEAE)1
Authors: Lee Connie M. , Osterbauer Nancy , Jiao Shuping , Fawley Marvin W.
Published: October 2004

The biosynthesis of the light‐harvesting complex (LHC) polypeptides of the green flagellate Mantoniella squamata (Manton et Parke) Desikachary (Micromonadophyceae, Chlorophyta) was examined by in vivo polypeptide labeling and immunoprecipitation of in vitro translation products. Using protein synthesis inhibitors, the LHC polypeptides were shown to be synthesized on 80S cytoplasmic ribosomes and not in the chloroplasts of cells. Poly (A)+ RNA was isolated and proteins were synthesized by a rabbit reticulocyte lysate system, with antisera raised against M. squamata LHC used for immunoprecipitation from the translation products. One polypeptide 3‐5 kDa larger than mature LHC polypeptides was immunoprecipitated. These studies indicate that although the LHC of M. squamata is quite different from the LHC of most green plants, the LHC polypeptides are synthesized as precursors in the cytoplasm of the cell and suggest that the genes encoding these polypeptides are located in the nucleus.
MONOCLONAL ANTIBODIES AS MOLECULAR MARKERS FOR THE INTRACELLULAR AND CELL WALL DISTRIBUTION OF CARRAGEENAN EPITOPES IN KAPPAPHYCUS (RHODOPHYTA) DURING TISSUE DEVELOPMENT1
Authors: Vreeland Valerie , Zablackis Earl , Laetsch Watson M.
Published: October 2004

Carrageenan, the major cell wall carbohydrate of certain red algae, is variable in structure and gelling properties. Sequence types include gelling (kappa and iota) and nongelling (lambda) types in addition to precursors, often in hybrid molecules containing more than one precursor and/or sequence type. Molecular markers to subunits were needed to study carrageenan synthesis, cell wall organization, and the relationship between structure and function. Monoclonal antibodies were produced to carrageenan, and their specificities were determined by competitive enzyme immunoassay. Antibodies were identified with specificities related to kappa, iota, and lambda carrageenan. The patterns of immunofluorescence localization on Kappaphycus alvarezii = Eucheuma alvarezii var. tambalang (Doty) sections were distinctive for each antibody. The antibody to a kappa‐related epitope labeled mature tissue strongly; antibodies to an iota‐related epitope and a lambda‐related epitope labeled weakly, consistent with the kappa‐enriched carrageenan produced by this alga. Kappa‐related epitopes were distributed throughout the wall and matrix, whereas iota‐related epitopes were concentrated in the middle lamella. Lambda‐related epitopes were localized primarily at the plant cuticle where kappa and iota antigens were lacking. An antibody appeared to be specific for a precursor of the gelling subunits because it showed maximal wall and intracellular labeling at the youngest developmental stage. All antibodies labeled intracellular inclusions in the transition zone between the epidermis and medulla during the development of medullary cells from the peripheral meristem in young branches. The results demonstrate the intracellular synthesis of epitopes related to all major carrageenan subunits and their differential extracellular distribution.
PHYLOGENY OF CARTERIA (CHLOROPHYCEAE) INFERRED FROM MOLECULAR AND ORGANISMAL DATA1
Authors: Buchheim Mark A. , Chapman Russell L.
Published: October 2004

Comparative ultrastructural data have shown that at least two distinct groups exist within Carteria. Similarly, interpretations of variation in gross morphological features have led to the discovery of morphologically distinct groups within the genus. Partial sequences from the nuclear‐encoded small‐ and large‐subunit ribosomal RNA molecules of selected Carteria taxa were studied as a means of 1) testing hypotheses that distinct groups of species exist within the genus and 2) assessing monophyly of the genus. Parsimony analysis of the sequence data suggests that three Carteria species, C. lunzensis, C. crucifera, and C. olivieri, form a monophyletic group that is the basal sister group to all other ingroup flagellate taxa (including species of Chlamydomonas, Haematococcus, Stephanosphaera, Volvox, and Eudorina). Two other Carteria taxa, C. radiosa and Carteria sp. (UTEX isolate LB 762), form a clade that is the sister group to a clade that includes Haematococcus spp., Chlamydomonas spp., and Stephanosphaera. Thus, the sequence data support the interpretations of ultrastructural evidence that described two distinct Carteria lineages. Moreover, the sequence data suggest that these two Carteria groups do not form a monophyletic assemblage. Parsimony analysis of a suite of organismal (morphological, ultra‐structural, life history, and biochemical) character data also suggest two distinct lineages among the five Carteria taxa; however, the organismal data are ambiguous regarding monophyly of these Carteria taxa. When the two independent data sets are pooled, monophyly of Carteria is not supported; therefore, the weight of available evidence, both molecular and organismal, fails to support the concept of Carteria as a natural genus.
ALEXANDRIUM SATOANUM SP. NOV. (DINOPHYCEAE) FROM MATOYA BAY, CENTRAL JAPAN1
Authors: Yuki Katsuhisa , Fukuyo Yasuwo
Published: October 2004

The gonyaulacoid dinofiagellate Alexandrium satoanum Yuki et Fukuyo sp. nov. is described from Matoya Bay, Pacific coast of central Japan. The species is distinctive in its conical epitheca with almost straight sides and dorsal concavity of the hypotheca. The plate formula is Po, pc, 4′, 6″, 6c, 10s, 5″″, and 2″″, including two accessory plates inside the sulcus. The apical pore plate is triangular and possesses an anterior attachment pore at the right margin. The first apical plate does not make contact with the apical pore plate and lacks a ventral pore. A posterior attachment pore lies at the center of the posterior sulcal plate. In Matoya Bay, vegetative cells occur as solitary cells or sometimes in pairs during late spring and early summer in low concentrations. In connection with this study, the following new combination is proposed: Alexandrium pseudogonyaulax (Biecheler) Horiguchi ex Yuki et Fukuyo comb. nov.
TEMPERATURE RESPONSES OF DISJUNCT TEMPERATE BROWN ALGAE INDICATE LONG‐DISTANCE DISPERSAL OF MICROTHALLI ACROSS THE TROPICS1
Authors: Peters Akira F. , Breeman Anneke M.
Published: October 2004

We examined the temperature tolerance of microscopic phases from geographically disjunct isolates of eight species or closely related, putatively conspecific taxa of temperate brown algae with disjunct distributions. Maximum within‐taxon differences were small and ranged from 1.6° to 4.3° C. Desmarestia aculeata and Sphaerotrichia divaricata, both with northern hemisphere amphioceanic distributions, showed little or no significant intraspecific variation between the mean upper survival limits (USL) of Atlantic and Pacific strains (δUSL ≤ 1.4°C), which would agree with a relatively recent separation of the respective populations. Among the plants with bipolar distributions, there was likewise very little difference (δUSL 0–1.1°C) between northern and southern hemisphere strains in Striaria attenuata and in the species pair Desmarestia viridis/D. willii. In Desmarestia ligulata, and in the species pairs Desmarestia firma/D. munda, Dictyosiphon foeniculaceus/D. hirsutus, and Scytothamnus australis/Scytothamnus sp., significant differences occurred, which indicate longer divergence times. δUSL in these cases ranged from 1.7° to 2.7°C, without overlap between strains from the northern and southern hemispheres. All species that passed the equator during cooler epochs had a USL of 26–27°C, at least in some geographical isolates. The NE Asian kelp Undaria pinnatifida, which passed the equator in recent times, had a USL of 29.6°C. We hypothesize that the mechanism of spreading in the amphipolar species studied was migration of vegetative microthalli. The more unlikely alternative hypothesis of continuous populations through the tropics during a cooler epoch would imply a drop in seawater temperatures to approximately 20° C in summer and 15° C in winter, which is not supported by paleoclimatic evidence.
AN OUTBREAK OF DOMOIC ACID POISONING ATTRIBUTED TO THE PENNATE DIATOM PSEUDONITZSCHIA AUSTRALIS1
Authors: Fritz Lawrence , Quilliam Michael A. , Wright Jeffrey L. C. , Beale Allison M. , Work Thierry M.
Published: October 2004

A bloom of the pennate diatom Pseudonitzschia australis Frenguelli (= Nitzschia pseudoseriata Hasle) occurring in Monterey Bay, California, in early September 1991 coincided with an episode of mortality in brown pelicans (Pelicanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus). High levels of domoic acid (DA), the amnesic shellfish poisoning toxin, were recorded in the plankton samples. Furthermore, high levels of DA, as well as numerous remnants of P. australis frustules, were found in the stomach contents of affected birds and in the visceral contents of local anchovies, a principal food source of seabirds. This is the first confirmed report of DA poisoning since the original 1987 episode in Atlantic Canada caused by Nitzschia pungens Grunow forma multiseries Hasle. It suggests another species of planktonic pennate diatom is capable of producing DA and that herbivorous finfish can act as vectors for this toxin.
DEGRADATION OF THE CELL‐WALL POLYSACCHARIDE OF PORPHYRIDIUM SP. (RHODOPHYTA) BY MEANS OF ENZYMATIC ACTIVITY OF ITS PREDATOR, GYMNODINIUM SP. (PYRROPHYTA)1
Authors: Simon Bracha , Geresh Shimona , Arad Shoshana (Malis)
Published: October 2004

The dinoflagellate Gymnodinium sp., which preys specifically on cells of the red microalga Porphyridium sp., possesses enzymes that degrade exocellular polysaccharides of the Porphyridium sp. A crude extract of Gymnodinium sp. was applied to this polysaccharide, and the degradation products were characterized by charge and size separations. Charge separation revealed the presence of a fraction that was not found in the native polysaccharide. This fraction, which was eluted from an anion‐exchange resin with water alone, was composed mostly of glucose and xylose (in a 1:1 weight ratio). Size separation of the degradation products revealed three fractions; the molecular weight of the main one was 5 × 106 daltons, whereas that of the native polysaccharide was 7 × 106 daltons. The carbohydrate composition of these fractions was determined. Although the main product of degradation had a relatively high molecular weight, its viscosity was significantly reduced relative to the native polysaccharide. Additional enzymatic degradation is required for further exploration of the structure of the exocellular polymer of Porphyridium sp.
PIGMENT TURNOVER IN THE MARINE DIATOM THALASSIOSIRA WEISSFLOGII. II. THE 14CO2‐LABELING KINETICS OF CAROTENOIDS1
Authors: Goericke Ralf , Welschmeyer Nicholas A.
Published: October 2004

The biosynthesis and turnover of the pigments fucoxanthin, diadinoxanthin (DD), and diatoxanthin (DT) were studied in exponentially growing cultures of the diatom Thalassiosira weissflogii (Grunow) Fryxell and Hasle to investigate the dependence of pigment turnover on algal growth rates and light intensity. 14C‐bicarbonate was used as a tracer. The labeling kinetics of fucoxanthin and DT were described satisfactorily by a simple precursor‐pigment model with two free parameters, the precursor and pigment turnover rate. At growth irradiances < 200 μE · m−2· s−1, labeling kinetics of DD indicated the presence of two kinetically distinct DD pools and at least one precursor pool. The average growth rate‐normalized pigment turnover rate of fucoxanthin was 0. The growth rate‐normalized turnover rate of DT, determined only at high light irradiances (> 200 μE·m−2·s−1), was 1.3. At high light irradiances, the growth rate‐normalized turnover rate of DD was 1.8. At low light irradiances, the turnover rates of the two DD pools were 3.7 and 0, respectively. The corresponding pigment turnover times were on the order of days to weeks, depending on the growth rate of the cultures. A comparison of pigment pool sizes, pigment turnover rates, and precursor turnover rates suggests that fucoxanthin is synthesized from a pool of DD and that DD and DT are synthesized from a common precursor, possibly β‐carotene. No evidence was seen for dynamic xanthophyll cycling. This suggests that the commonly known “xanthophyll cycle” is the simple unidirectional conversion of DD into DT, or of DT into DD, in response to rapid irradiance changes.
A PERSISTENT VIRUS INFECTION IN FELDMANNIA (PHAEOPHYCEAE)1
Authors: Henry Eric C. , Meints Russel H.
Published: October 2004

A virus infection is described within the unilocular sporangia of Feldmannia sp., a filamentous brown alga (Phaeophyceae). The alga is easily maintained in culture and vegetative growth is vigorous, but formation of icosahedral virions 150 nm in diameter completely displaces production of zoospores. The viruses, estimated at 1–5 × 106 per sporangium, are eventually released by rupture of the sporangial wall. Deoxyribonucleic acid (DNA) isolated from the viruses can be readily digested with restriction endonucleases and consists of ca. 170 kbp of double‐stranded DNA.