Higher plant origins and the phylogeny of green algae.

5S rRNA sequences from six additional green algae lend strong molecular support for the major outlines of higher plant and green algae phylogeny that have been proposed under varying naming conventions by several authors. In particular, the molecular evidence now available unequivocally supports the existence of at least two well-separated divisions of the Chlorobionta: the Chlorophyta and the Streptophyta (i.e., charophytes) (according to the nomenclature of Bremer). The chlamydomonad 5S rRNAs are, however, sufficiently distinct from both clusters that it may ultimately prove preferable to establish a third taxon for them. In support of these conclusions 5S rRNA sequence data now exist for members of four diverse classes of chlorophytes. These sequences all exhibit considerably more phylogenetic affinity to one another than any of them show toward members of the other cluster, the Streptophyta, or the two Chlamydomonas strains. Among the Charophyceae, new 5S rRNA sequences are provided herein for three genera, Spirogyra, Klebsormidium, and Coleochaete. All of these sequences and the previously published Nitella sequence show greater resemblance among themselves and to the higher plants than they do to any of the other green algae examined to date. These results demonstrate that an appropriately named taxon that includes these green algae and the higher plants is strongly justified. The 5S rRNA data lack the resolution needed, however, to unequivocally determine which of several subdivisions of the charophytes is the sister group of the land plants. The evolutionary diversity of Chlamydomonas relative to the other green algae was recognized in earlier 5S rRNA studies but was unanticipated by ultrastructural work.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation of the phylogenetic position of the dinoflagellate Crypthecodinium cohnii based on 5S rRNA characterization.

Partial nucleotide sequences for the 5S and 5.8S rRNAs from the dinoflagellate Crypthecodinium cohnii have been determined, using a rapid chemical sequencing method, for the purpose of studying dinoflagellate phylogeny. The 5S RNA sequence shows the most homology (75%) with the 5S sequences of higher animals and the least homology (less than 60%) with prokaryotic sequences. In addition, it lacks certain residues which are highly conserved in prokaryotic molecules but are generally missing in eukaryotes. These findings suggest a distant relationship between dinoflagellates and the prokaryotes. Using two different sequence alignments and several different methods for selecting an optimum phylogenetic tree for selecting an optimum phylogenetic tree for a collection of 5S sequences including higher plants and animals, fungi, and bacteria in addition to the C. cohnii sequence, the dinoflagellate lineage was joined to the tree at the point of the plant-animal divergence well above the branching point of the fungi. This result is of interest because it implies that the well-documented absence in dinoflagellates of histones and the typical nucleosomal subunit structure of eukaryotic chromatin is the result of secondary loss, and not an indication of an extremely primitive state, as was previously suggested. Computer simulations of 5S RNA evolution have been carried out in order to demonstrate that the above-mentioned phylogenetic placement is not likely to be the result of random sequence convergence. We have also constructed a phylogeny for 5.8S RNA sequences in which plants, animals, fungi and the dinoflagellates are again represented. While the order of branching on this tree is the same as in the 5S tree for the organisms represented, because it lacks prokaryotes, the 5.8S tree cannot be considered a strong independent confirmation of the 5S result. Moreover, 5.8S RNA appears to have experienced very different rates of evolution in different lineages indicating that it may not be the best indicator of evolutionary relationships. We have also considered the existing biological data regarding dinoflagellate evolution in relation to our molecular phylogenetic evidence.

Deoxyribonucleic acid sequence organization in the genome of the dinoflagellate Crypthecodinium cohnii.

Details of the general DNA sequence organization in the dinoflagellate Crypthecodinium cohnii have been obtained by using hydroxylapatite binding experiments, S1 nuclease digestion .and electron microscopy of reassociated DNA. It has been found that roughly half of the genome is made up of unique sequences interspersed with repeated sequence elements with a period of approximately 600 nucleotides. This class represents roughly 95% of the total number of interspersed unique elements in the genome. The remaining 5% are uninterrupted by repeated sequences for at least 4000 nucleotide pairs. The interspersed repeated elements are narrowly distributed in length with 80% under 300 nucleotide pairs in length. About half of the repeated DNA (20-30% of the genome) is not interspersed among unique sequences. The close spacing of the short repeats interspersed throughout much of the genome is consistent with the occurrence of the huge network structures observed in the electron microscope for low Cot reassociation of moderately long fragments. An unusual class of heteroduplexes was detected in the electron microscope which is believed to derive from the reassociation of repeated sequences from different families which are frequently found adjacent to one another in different locations in the genome. The occurrence of this novel arrangement of repeated sequences may reflect the unusual organization of the dinoflagellate nucleus. However, in most respects the sequence arrangement in this unicellular alga is very typical of higher plants and animals.

A newly revised classification of the protozoa.

The subkingdom Protozoa now inclues over 65,000 named species, of which over half are fossil and approximately 10,000 are parasitic. Among living species, this includes approximately 250 parasitic and 11,300 free-living sarcodines (of which approximately 4,600 are foraminiferids); approximately 1,8000 parasitic and 5,100 free-living flagellates; approximately 5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and approximately 2,5000 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unnamed. Seven phyla of PROTOZOA are accepted in this classification--SARCOMASTIGOPHORA, LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and reporesentative genera of each are named. The present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of nex taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporatesmost of the major changes that will be made for some time, and that it will be used for many years by both protozoologist and non-protozoologists.

DNA organization of Methanobacterium thermoautotrophicum.

The organism Methanobacterium thermoautotrophicum, an archaebacterium, is envolutionarily very distant from both traditional prokaryotes and eukaryotes. Its genome (DNA) has physical characteristics typical of most prokaryotes except that it is quite small (about 10(9) daltons, less than half the size of the genome of Escherichia coli) and contains a significant amount (6 percent) DNA which renatures extremely rapidly.

N-methyl-N'-nitro-N-nitrosoguanidine and UV induced mutants of the dinoflagellate Crypthecodinium cohnii.

Mutant strains were chemically induced by treatment with N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV irradiation. UV and NTG mutation rates were obtained that were both consistent with the organism being haploid. Three types of mutants were produced: (a) strains deficient in both beta- and gamma-carotene, the only carotenoids found in the wild type; phenotypes include albinos (translucent, dull white, "snow white") and cream-colored on agar as compared to the yellow-orange color of wild type colonies; (b) strains requiring adenine, guanine or cytosine in addition to the minimal medium for growth; (c) mutants that grow at a rate less than 40% of the wild type in minimal medium.

Dinoflagellate evolution: speculation and evidence.

Nuclear features of dinoflagellates that were used originally to support the Mesocaryota concept are reviewed. The fibrillar diameter of dinoflagellage chromatin, low level of chromosomal basic proteins, membrane attachment of chromosomes and swirl pattern observed in sectioned chromosomes are features that support a prokaryotic affinity. The presence of repeated and highly complex DNA, a S-phase of DNA synthesis in the cell cycle, presence of basic proteins, and the reinterpretation of extranuclear microtubules as a spindle support the contention that dinoflagellates are eukaryotes. This combination of prokaryotic and eukaryotic features suggests that dionflagellates are a geologically old group and that perhaps they diverged from the higher eukaryotic lineage before evolution of eukaryotic chromatin but after the evolution of repeated DNA. The 2 patterns of carotenoid composition exemplified by the presence of peridinin or fucoxanthin suggest separate origins of dinoflagellate plastids, perhaps by prokaryotic and eukaryotic capture. It is suggested that the species possessing fucoxanthin obtained their plastids by capture of photosynthetic eukaryotes.

Characterization of the DNA from the dinoflagellate Crypthecodinium cohnii and implications for nuclear organization.

Although dinoflagellates are eucaryotes, they possess many bacterial nuclear traits. For this reason they are thought by some to be evolutionary intermediates. Dinoflagellates also possess some unusual nuclear traits not seen in either bacteria or higher eucaryotes, such as a very large number of identical appearing, permanently condensed chromosomes suggesting polyteny or polyploidy. We have studied the DNA of the dinoflagellate Crypthecodinium cohnii with respect to DNA per cell, chromosome counts, and renaturation kinetics. The renaturation kinetic results tend to refute extreme polyteny and polyploidy as the mode of nuclear organization. This organism contains 55-60% repeated, interspersed DNA typical of higher eucaryotes. These results, along with the fact that dinoflagellate chromatin contains practically no basic protein, indicate that dinoflagellates may be organisms with a combination of both bacterial and eucaryotic traits.

Genetic recombination in the dinoflagellate Crypthecodinium cohnii.

Genetic recombination in dinoflagellates has been detected with the use of chemically induced carotene-deficient mutants of Crypthecodinium cohnii.

Chloroplast pigments of the marine dinoflagellateGyrodinium resplendens.

The photosynthetic marine dinoflagellate,Gyrodinium resplendens, was grown axenically and harvested during logarithmic growth for analysis of its lipid-soluble pigments. Chlorophylla and 8 carotenoids were isolated from the methanol and acetone extract by column and thin-layer chromatography. Chlorophyllc was isolated by partitioning the total extract between saline aqueous acetone and hexane.Absorption spectra taken in hexane, ethanol, methanol and carbon disulfide confirm the presence of beta-carotene, peridinin, dinoxanthin and diadinoxanthin as major carotenoids.Four new minor xanthophylls are also described, one of which, namedpyrrhoxanthin, resembles an alkali-labile keto-epoxide. At least one of the minor xanthophylls occurs as an ester.Diadinoxanthin fromGyrodinium and antheraxanthin fromEuglena gracilis seem to be identical with respect to absorption curves, polarity, number of 5, 6-epoxy groups and lack of allylic hydroxyl groups; however, co-chromatography of stereoisomers after iodine-isomerization showed slight differences.Most of the carotenoids are further characterized here by their partition ratios between hexane and 95% methanol. Several of the carotenoids were tested for the presence of 5, 6-epoxy and allylic hydroxyl groups. Four of the pigments, comprising 91% of the total carotenoids are revealed as 5,6-monoepoxides by their instability toward dilute acid. One carotenoid resembles a diepoxide.

A UNIQUE COLONIAL MARINE CENTRIC DIATOM, COENOBIODISCUS MURIFORMIS GEN. ET SP. NOV.(1).

A new colonial centric marine diatom, Coenobio-discus muriformis gen. et sp. nov. (family Coscinodiscaceae) has been found in San Diego Bay, San Diego, California. The colony is composed of a single layer of 200-530 cells linked girdle to girdle by a compartmentalized matrix. The colony has the shape of a slightly concavo-convex disk approximately 400 µ. in diameter. Each cell is about 10 µ, in diameter and the valves have many structural features in common with those of Thalassiosira. The organic matrix contains 6-11 partitions that radiate from each cell, forming a number of extracellular chambers. The organic matrix does not contain chitin or cellulose as a major constituent. Histochemical similarities are found with the capsular and tubular material of previously described diatoms. The colonies reproduce without passing through a unicellular vegetative stage.

Food value of red tide (Gonyaulax polyedra).

Two harvests of ocean-growing red tide, comprised mainly of Gonyaulax polyedra, were evaluated in limited trials of rat feeding. The protein of red tide (25 to 30 percent, dry basis) supported growth satisfactorily. The essential amino acid composition of the protein closely resembles that of casein, the major protein of milk. As a marine resource, plankton represents a challenge for research.