Chromophyte Algae Research Articles

Characterisation of a chloroplast-encoded sec Y homologue and atpH from a chromophytic alga Evidence for a novel chloroplast genome organisation

sec Y is a prokaryotic gene that encodes the SecY protein, an integral membrane component of the prokaryotic protein translocation apparatus. A chloroplast-encoded sec Y homologue has been identified in the unicellular, chromophytic alga, Pavlova lutherii. The gene predicts a protein composed of ten membrane-spanning regions, that is approximately 25% homologous and 50% similar to bacterial and plastid SecY proteins. The sec Y gene from P. lutherii is independent of the ribosomal protein ( rp) gene cluster to which it is closely linked in other organisms. In P. lutherii sec Y is located 5′ to atpI and atpH. Since, in higher plants the atpIHFA gene cluster and the rp gene cluster are separated by approximately 50 kb, we conclude, this indicates a novel chloroplast gene arrangement in P. lutherii.

Gene phylogenies and the endosymbiotic origin of plastids

The endosymbiotic origin of chloroplasts from cyanobacteria has long been suspected and has been confirmed in recent years by many lines of evidence. Debate now is centered on whether plastids are derived from a single endosymbiotic event or from multiple events involving several photosynthetic prokaryotes and/or eukaryotes. Phylogenetic analysis was undertaken using the inferred amino acid sequences from the genes psbA, rbcL, rbcS, tufA and atpB and a published analysis (Douglas and Turner, 1991) of nucleotide sequences of small subunit (SSU) rRNA to examine the relationships among purple bacteria, cyanobacteria and the plastids of non-green algae (including rhodophytes, chromophytes, a cryptophyte and a glaucophyte), green algae, euglenoids and land plants. Relationships within and among groups are generally consistent among all the trees; for example, prochlorophytes cluster with cyanobacteria (and not with green plastids) in each of the trees and rhodophytes are ancestral to or the sister group of the chromophyte algae. One notable exception is that Euglenophytes are associated with the green plastid lineage in psbA, rbcL, rbcS and tufA trees and with the non-green plastid lineage in SSU rRNA trees. Analysis of psbA, tufA, atpB and SSU rRNA sequences suggests that only a single bacterial endosympbiotic event occurred leading to plastics in the various algal and plant lineages. In contrast, analysis of rbcL and rbcS sequences strongly suggests that plastids are polyphyletic in origin, with plastids being derived independently from both purple bacteria and cyanobacteria. A hypothesis consistent with these discordant trees is that a single bacterial endosymbiotic event occurred leading to all plastids, followed by the lateral transfer of the rbcLS operon from a purple bacterium to a rhodophyte.

Structural organization of the chloroplast genome of the chromophytic algaVaucheria bursata

The chloroplast genome of the chromophytic alga Vaucheria bursata has been characterized by restriction site and gene mapping analysis. It is represented by a circular molecule 124.6 kb in size. An inverted sequence duplication (IR) not larger than 5.85 kb carries the rRNA genes and separates two single-copy regions of 64.6 kb and 48.3 kb from one another. The Vaucheria plastid genome exists in two equimolar isomers which is due to intramolecular flip-flop recombination within the IR sequences. The coding sites for 21 structural and soluble proteins have been mapped on both single-copy regions using heterologous gene sequences as probes. Although the overall gene order is found to be rearranged when compared with other chromophytic algal and land plant chloroplast genomes, most of the transcriptional units of cyanobacteria and land plant chloroplast genomes appear to be conserved. The phylogenetic implications of these findings are further discussed.

Pre-Ediacaran multicellular life: harbinger of a Phanerozoic radiation

Multicellular organisms must have had a substantial pre-Ediacaran history, but the fossil evidence is sparse and often equivocal. The taxonomic resolution necessary to constrain phylogenetic hypotheses is limited largely to Lagerstätte-grade fossils that retain evidence of diagnostic cell division patterns. Uniseriate and multiseriate filaments in the 1267-723 Ma Hunting Formation, Somerset Island, derive from transverse and longitudinal intercalary cell division programs indistinguishable from those of the modern red alga Bangia, and establish a significantly pre-Ediacaran datum point for the Rhodophyta. Likewise, on the basis of a distinctive “segregative cell division”, three taxa of siphonocladalean green algae (Chlorophyta) are identified in the ca. 750 Ma Svanbergfjellet Formation, Spitsbergen. Process-bearing vesicles in the Svanbergfjellet sequence further compare with the germinating zoospores of the modern chromophyte alga Vaucheria, while convincing Vaucheria-like thalli are reported from ca. 900 Ma deposits in Siberia. The broad co-occurrence of multicellular Rhodophyta, Chlorophyta, and Chromophyta by at least 750 Ma ago accords well with molecular evidence that suggests the three principal algal clades diverged from a common ancestor during a brief but marked radiation relatively late in eukaryote evolution.Complex multicellularity featuring cellular and tissue(?) differentiation is also encountered in the pre-Ediacaran fossil record. A large ornate form in the Svanbergfjellet succession preserves at least six readily distinguishable cell types and, despite its taxonomic uncertainty, can be characterized as at least as complex as the most complex modern algae or fungi. No cellularity is preserved in the late Proterozoic macrofossil Tawuia; however, SEM and light microscopy of its isolated wall reveal a complex histology suggestive of a relatively advanced grade of multicellularity. Another Svanbergfjellet macrofossil has a distinct wall structure and bears a terminal pair of large reniform structures; if these prove to be truly bilaterally symmetrical, this fossil represents a grade of organization otherwise not recognized until the Ediacaran. Further analysis of these and other pre-Ediacaran ‘problematica’ may clarify their taxonomic relationships and promises to resolve at least some of the ‘Cambrian explosion’ into a meaningful sequence of evolutionary change.

Characterization of Satellite DNA from Three Marine Dinoflagellates (Dinophyceae): Glenodinium sp. and Two Members of the Toxic Genus, Protogonyaulax

Using CsCl-Hoechst dye or CsCl-ethidium bromide gradients, satellite and nuclear DNAs were separated and characterized in three marine dinoflagellates: Glenodinium sp., and two toxic dinoflagellates, Protogonyaulax tamarensis and Protogonyaulax catenella. In all three dinoflagellates, the lowest density fraction, satellite DNA(1), hybridized to chloroplast genes derived from terrestrial plants and/or other algae. Dinoflagellate chloroplast DNAs exhibited molecular sizes of 114 to 125 kilobase pairs, which is consistent with plastid sizes determined for other chromophytic algae (120-150 kilobase pairs). Mitochondrial DNA was not resolved from nuclear DNA in this system. Two additional satellite DNAs, satellite DNA(2) and satellite DNA(3), recovered from P. tamarensis and P. catenella were similar to one another, both within and between species, when characterized by restriction enzyme analysis. These satellites were 85 to 95 kilobase pairs in size, and exhibited restriction fragments that hybridized to yeast nuclear ribosomal RNA genes. Restriction enzyme analyses and DNA hybridization studies of cpDNA document that the two Protogonyaulax isolates are not evolutionarily identical.

Thylakoid Organization in the Chromophyte Alga Ochromonas danica

This report describes the isolation and preliminary characterization of a new pigment-protein complex from the chromophyte alga, Ochromonas danica. The pigment-protein complex was obtained by extracting a thylakoid membrane preparation with the zwitterionic detergent lauryldimethylamine oxide followed by ultracentrifugation on sucrose gradients. The pigment-protein complex has been characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, absorption spectroscopy, and low temperature (77 Kelvin) chlorophyll fluorescence spectroscopy. A polypeptide with a monomeric molecular weight of 31,000 as determined by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis was the major constituent of this pigment-protein complex. The major pigment in this complex was chlorophyll a, although an as yet unidentified carotenoid was also present. There was no evidence for the presence of chlorophyll c.

In Vivo and In Vitro Protein Phosphorylation Studies on Ochromonas danica, an Alga with a Chlorophyll a/c/Fucoxanthin Binding Protein

The phosphorylation of thylakoid membranes in the Chromophyte alga Ochromonas danica was studied in whole cells and in vitro. Protein kinase activity was observed in the thylakoid fraction, and several membrane-bound polypeptides were found to be phosphorylated. The thylakoid protein kinase demonstrated several unusual regulatory properties. Both the polypeptides that were phosphorylated and the rate of protein phosphorylation were independent of illumination. Protein kinase activity was also unaffected by 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron. The kinase activity was inhibited under strong reducing conditions. Whole cells labeled with (32)PO(4) (3-) were converted to light states I and II by pre-illumination favoring photosystem I or photosystem II, respectively. Analysis of the phosphoproteins from cells in state I and state II showed that no changes in phosphorylation accompanied the change in energy redistribution.

Green, J. C, Leadbeater, B. S. C. & Diver, W. L. (eds), 1990. The Chromophyte Algae: Problems and Perspectives.

Green, J. C, Leadbeater, B. S. C. & Diver, W. L. (eds), 1990. The Chromophyte Algae: Problems and Perspectives.

A NEW PHYLOGENY FOR CHROMOPHYTE ALGAE USING 16S‐LIKE RRNA SEQUENCES FROMMALLOMONAS PAPILLOSA(SYNUROPHYCEAE) ANDTRIBONEMA AEQUALE(XANTHOPHYCEAE)1

ABSTRACTThe 16S‐like ribosomal RNA genes fromMallomonas papillosaHarris et Bradley (Synurophyceae) andTribonema aequalePascher (Xanthophyceae) were sequenced and compared to those of other eukaryotes.Mallomonasis closely related toOchromonas(Chrysophyceae) and supports the general hypothesis of a close phylogenetic relationship between the Synurophyceae and Chrysophyceae.Tribonemais specifically related toCostaria costata(C. A. Agardh) Saunders (Phaeophyceae) demonstrating an unexpected phylogenetic relationship between the Xanthophyceae and Phaeophyceae. Distance and parsimony analysis place these four chromophyte genera in a complex evolutionary assemblage that includes the Bacillariophyceae and Oomycetes but excludes the Dinophyceae. The close relationship between the chromophyte algae and the Öomycete fungi supports the hypothesis that protists with tripartite hairs form a natural assemblage.

Isolation, physical map and gene map of mitochondrial DNA from the cryptomonad Pyrenomonas salina

Mitochondrial DNA (mtDNA) from the cryptomonad Pyrenomonas salina was isolated by CsCl-buoyant density centrifugation of whole-cell DNA in the presence of Hoechst dye 33258. mtDNA consists of circular molecules about 47 kb in size as estimated from restriction enzyme analysis. A physical map for six restriction enzymes (Bam HI, Bge I, Eco RI, Pst I, Sac I and Sal I) has been constructed. Genes coding for the small subunit of rRNA, cytochrome oxidase subunits I and II, and apocytochrome b were localized on this map using Southern blot hybridization with heterologous gene probes from Oenothera. Genes for 5S rRNA and NADH dehydrogenase subunit 5 are absent from P. salina mtDNA. The mitochondrial genome, being the first analysed to this extent in chromophytic algae, should be valuable for taxonomic and phylogenetic studies.

Structural features of the plastid ribosomal RNA operons of two red algae: Antithamnion sp. and Cyanidium caldarium

The nucleotide sequences of the plastid 16S rDNA of the multicellular red alga Antithamnion sp. and the 16S rDNA/23S rDNA intergenic spacers of the plastid DNAs of the unicellular red alga Cyanidium caldarium and of Antithamnion sp. were determined. Sequence comparisons support the idea of a polyphyletic origin of the red algal and the higher-plant chloroplasts. Both spacer regions include the unsplit tRNA(Ile)(GAU) and tRNA(Ala)(UGC) genes and so the plastids of both algae form a homogeneous group with those of chromophytic algae and Cyanophora paradoxa characterized by 'small-sized' rDNA spacers in contrast to green algae and higher plants. Nevertheless, remarkable sequence differences within the rRNA and the tRNA genes give the plastids of Cyanidium caldarium a rather isolated position.

Cryptomonad algae are evolutionary chimaeras of two phylogenetically distinct unicellular eukaryotes

Although it is widely accepted that the plastids of plants and algae originated as endosymbionts, the details of this evolutionary process are unclear. It has been proposed that in organisms whose plastids are surrounded by more than two membranes, the endosymbiont was a eukaryotic alga rather than a photosynthetic prokaryote. The DNA-containing nucleomorph of cryptomonad algae appears to be the vestigial nucleus of such an algal endosymbiont. Eukaryotic-type ribosomal RNA sequences have been localized to a nucleolus-like structure in the nucleomorph. In support of the hypothesis that cryptomonads are evolutionary chimaeras of two distinct eukaryotic cells, we show here that Cryptomonas phi contains two phylogenetically separate, nuclear-type small-subunit rRNA genes, both of which are transcriptionally active. We incorporate our rRNA sequence data into phylogenetic trees, from which we infer the evolutionary ancestry of the host and symbiont components of Cryptomonas phi. Such trees do not support the thesis that chromophyte algae evolved directly from a cryptomonad-like ancestor.

Development and evaluation of tracer particles for use in microzooplankton herbivory studies

Two methods of preparing algae for use as tracer particles in single species measurements of microzooplankton herbivory were evaluated. Algae were either heat-killed and labelled with 5-(4,6dichlorotriazin-2-yl amino fluorescein) (DTAF) (Rublee & Gallegos 1989; Mar. Ecol. Prog. Ser. 51: 221-227) or stained with hydroethidine (HYD). Both DTAF and HYD-stained algae were readily visible within the digestive vacuoles of most microzooplankton collected in estuarine and coastal waters of Massachusetts (USA) and preserved with Lugol's iodine. However, DTAF was ineffective at staining several chromophytic algae and the heat-kill process reduced cell volume by 2 50 % in several of the algae which were effectively stained. HYD effectively stained all algae tested except chlorophytes. Staining with HYD had negligible effects on cell size or morphology but reduced photosynthesis in Isochrysis galbana by about 95 %. Ingestion rates of field populations of ciliates differed by up to 25-fold for 2 algal species (I. galbana and Pyramimonas sp.). For a ciliate (Strombidinopsis sp.) which ingested Pyramimonas sp. at a high rate relative to I. galbana, ingestion rates for live HYD-stained Pyra~nimonas sp. were about twice as high as for the same alga heat-killed and stained with DTAF. In cultures of Strobilidium sp., ingestion of HYD-stained and untreated I. galbana radiolabelled with I4C were similar at concentrations up to 1.6 x 104 cells ml-' HYD dissolved in seawater had negligible effects on ciliate grazing rate at concentrations up to 0.29 $g ml-l. HYD-stained algae are a new tool for quantifying microzooplankton herbivory which should be particularly useful in examining feeding preferences among field populations.

Cladistic methods and chromophyte phylogeny

An examination of systematic methods is undertaken to establish interrelationships within the chromophytic algae, focussing on their relationship to the Oomycota. Evidence from both molecular and morphological studies suggests that the Oomycota appeared before the pigmented chromophytes. Theories on the origin of the chromophyte chloroplast are examined in the light of these findings.

Sequence and secondary structure of chloroplast 16S rRNA from the chromophyte algaOlisthodiscus luteus, as inferred from the gene sequence

Sequence and secondary structure of chloroplast 16S rRNA from the chromophyte alga<i>Olisthodiscus luteus</i>, as inferred from the gene sequence

The Chromophyte Algae: Problems and Perspectives

T. Christensen: The Chromophyta, past and present S.W. Jeffrey: Chlorophyll c pigments and their distribution in the chromophyte algae T. Bjornland and S. Liaaen-Jensen: Distribution patterns of carotenoids in relation to chromophyte phylogeny and systematics J.A. Raven, A.M. Johnston, and M. bin Surif: The photosynthetic apparatus as a phyletic character R.A. Cattolico: Analysis of chloroplast evolution and phylogeny K.V. Kowallik: Molecular aspects and phylogenetic implications of plastid genomes of certain chromophytes J.M. Whatley: Chromophyte chloroplasts - a polyphylectic origin? B.S.C. Leadbeater: The phylogenetic significance of flagellar hairs in the Chromophyta H.R. Preisig: The flagellar base ultrastructure and phylogency of chromophytes J.C. Green: Relationships between the chromophyte algae: the evidence from studies of mitosis J.D. Dodge: Phylogenetic relationships of dinoflagellates and their plastids M.N. Clayton: Brown algae and chromophyte phylogeny C.J. O'Kelly: The evolutionary origin of the brown algae: information from studies of motile cell structure P. Heywood: Some affinities of the Raphidophyceae with other chromophyte algae R.M. Crawford and F.E. Round: Corethron and Mallomonas - some striking morphological similarities C.G. Mann and H.J. Marchant: The origins of the diatom and its life cycle G.W. Beakes: Oomycete fungi: their phylogeny and relationship to chromophyte algae D.J.S. Barr and N.L. Desaulniers: The flagellar apparatus of the Oomycetes and Hyphochytriomycetes D.J. Patterson: Stramenopiles: chromophytes from a protistan perspective T. Cavalier-Smith: The Kingdom Chromista F.E. Round: The chromophyte algae - problems and perspectives. A summarizing view. Index.

NUCLEOTIDE SEQUENCE OF THE GENE FOR THE LARGE SUBUNIT OF RIBULOSE‐1.5‐DISPHOSPHATE CARBOXYLASE/OXYGENASE FROM CRYPTOMNASΦ EVIDENCE SUPPORTING THE POLYPHYLETIC ORGIN OF PLASTIDS1

ABSTRACTThe Chloroplast‐encoded gene for the large subunit of ribulose‐1, 5‐bisphosphate carboxylase/oxygenase (Rubisco) from the marine chlorophyll c2‐, phycobiliprotein‐containing alga, Cryptomonas φ was cloned, sequenced and compared to representatives from other groups of photosynthetic organisms. The coding sequence was 1464 base pairs(bp) and encoded a polypeptide of 488 amino acids. The small subunit of Rubisco was located 83 bp 3′ to the large subunit and was co‐transcribed. A 5 bp sequence, 5′ of the initiator methionine codons of both the large and small subunits, may represent ribosomal binging sites. The start of transcription was identified by primer extension studies and putative promotor sequences were found. This study is the first report of the sequence for the large subunit of Rubisco from a chromophyte alga, and its potential as phylogenetic indicator for algal plastids sis discussed.

EVIDENCE THAT THE NUCLEOMORPHS OF CHLORARACHNION REPTANS (CHLORARACHNIOPHYCEAE) ARE VESTIGIAL NUCLEI: MORPHOLOGY, DIVISION AND DNA‐DAPI FLUORESCENCE1

ABSTRACTChlorarachnion reptans Geitler shows affinities to both the Chlorophyceae and the chloroplast endoplasmic reticulum‐containing chromophyte algae in possessing chlorophyll b and chloroplasts which are limited by four membranes, respectively. In the periplastidal compartment surrounding each of the four to eight chloroplasts of a C. reptans cell are putative eukaryotic‐sized ribosomes, scattered tubules and vesicles, and a small double‐membrane‐limited nucleus‐like organelle named the nucleomorph. The nucleomorphs display 4′‐6‐diamidino‐2‐phenylindole (DAPI)fluorescence which is sensitive to DNase digestion, but not to treatment with RNase. The nucleomorphs also contain a fibrillogranular body which resembles a nucleolus. Nucleomorph division occurs by the sequential infolding of the inner and outer envelope membranes and subsequent constriction in two, with no involvement of microtubules. In all these characteristics, the nucleomorphs of C. reptans are similar to the cryptomonad nucleomorph which has been hypothesized to be the vestigial nucleus of an ancestral red alga which gave rise to the chloroplasts of the Cryptophyceae. The presence of chlorophyll b and the contents and morphology of C. reptans chloroplast compartments suggest a green algal origin for the chloroplasts of these cells. The discovery of a second organism with a DNA‐containing, nucleus‐like organelle in its chloroplast compartment lends strong support to the hypothesis that the chloroplasts of many algae have evolved from eukaryotic endosymbionts.

Occurrences of Silica-Scaled Chromophyte Algae in Predominantly Alkaline Lakes and Ponds in Iowa

-Lentic water bodies in Iowa, USA, were examined for the presence of silicascaled chromophyte algae (Synurophyceae, Chrysophyceae). Silica-scaled species were encountered in samples from all seasons of the year and in water with pH measurements ranging from 5.7-8.7. Based upon qualitative electron microscopic observations, 34 taxa were identified in 27 collections. Temperature, pH and specific conductance were measured for each collection. Of the commonly observed taxa in this survey, Chrysosphaerella brevispina was relatively stenothermic, occurring in six collections with a temperature range of 2-11 C. Synura echinulata was observed only in the five most acidic collections, pH 5.7-6.6. Mallomonas tonsurata, M. pseudocoronata, M. acaroides and M. caudata were common in relatively alkaline collections and may form an assemblage of silica-scaled species common in alkaline prairie habitats. Future research directions suggested by these data are discussed.

Preservation of long-wavelength fluorescence in the isolated thylakoids of two phytoplanktonic algae at 77 K

Loss of long-wavelength fluorescence upon isolation of chloroplasts or thylakoids has long been a problem in studies of the chromophyte algae, that is, algae possessing chlorophyll c and related algae. We now report the preservation of long-wavelength fluorescence, using two such algae, Phaeodactylum tricornutum (Bacillariophyta) and Vischeria helvetica (Eusigmatophyta). Preservation was achieved using an isolation buffer of high osmotic and ionic strength. Anions high on the Hofmeister series were more efficient than anions low on the Hofmeister series. The most efficient buffer was one high in phosphate (0.5 M) and citrate (0.3 M) combined with 0.3 M sucrose. The results indicate that there are basic differences at the molecular level between the arrangement in the thylakoid membrane of chlorophyll-protein complexes of the chromophyte and related algae compared to green algae and higher plants.