Protonema mit Riesenkern bei der siphonalen GrünalgeBryopsis hypnoides und weitere cytologische Befunde

Zusammenfassung 1. Die in Kulturen erhaltenen Zygoten vonBryopsis hypnoides keimen ohne Ruheperiode aus zu einem Protonema mit ein oder mehreren pfriemförmigen Ästen von begrenztem Wachstum, die sich mehr oder weniger aufrecht auf einem prostraten rhizoidalen Teil erheben.2. Im Gegensatz zu dem vielkernigen Thallus der gefiederten Alge besitzt das Protonema einen einzigen großen Kern, der den achtfachen Durchmesser der vegetativen Kerne des Fiederthallus erreichen kann. Dieser Riesenkern enthält einen langgewundenen Nucleolus, der in Gestalt und Entwicklung Ähnlichkeit mit dem Nucleolus des Riesenkerns vonAcetabularia besitzt. Im Nucleolus wurde RNS nachgewiesen.3. Das Protonema wird vielkernig vor der Entstehung ein bis mehrerer breiterer Triebe, die sich zu den bekannten Fiederthalli oder zu Rhizoiden ausbilden.4. Das Teilungsbild des Riesenkerns wird von einer hantelförmigen Spindel des sich teilenden Nucleolus beherrscht, an deren Peripherie eine Mitose diploider Größenordnung zu erkennen ist. Der Riesenkern löst sich anschließend auf und entläßt nacheinander 2 Sekundärkerne, die sich mitotisch vermehren.5. Der relativ große Nucleolus der Thalluskerne bleibt ebenso wie die Kernmembran während der Mitose erhalten. Er wird in der Anaphase stark gestreckt, und die Verbindung zwischen den Tochternucleolen löst sich oft erst in der Telophase.6. Während der Gametenbildung in den Fiedern wird die Chromosomenzahl von 2n=16 auf n=8 reduziert.7. Anisogame Kopulation wurde beobachtet.

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Protonema with giant nucleus in the siphonaceous green algaBryopsis hypnoides and additional cytological results

Zygotes ofBryopsis hypnoides, maintained in modified Schreiber-solution, germinate into a rhizoidal protonema with a single nucleus; the nucleus diameter increases up to eight times that of vegetative nuclei in the multinucleate thallus. The giant nucleus contains a long sinuous nucleolus similar to that ofAcetabularia. The protonema becomes multinucleate prior to the formation of the plumose thalli. The division of the giant nucleus has been observed: Chromosomes in mitotic configuration, apparently diploid, become visible at the periphery of a large dumbbell-shaped spindle formed by the dividing nucleolus. Subsequently, the giant nucleus dissolves and dismisses two small nuclei, which propagate mitotically. Further observations deal with the persistence of the nucleolus during mitosis, chromosome number, gamete formation, and gamete copulation.

     

COMPARATIVE ULTRASTRUCTURE OF THE PRIMARY NUCLEUS IN BRYOPSIS AND ACETABULARIA1,2

The fine structure of the primary nucleus in Bryopsis hypnoides was compared with that of the primary nucleus in Acetabularia calyculus and Batophora oerstedii. In Bryopsis the mature primary nucleus contains a peripheral reticulum composed of 4–6 layers of 200 A diameter fibrils. The nuclear membrane has numerous nuclear pores that are located adjacent to the openings in the layers of the reticulum. Each nuclear pore is constituted of peripheral globular elements and a central granule. Although pores of similar structure are present in the nuclear envelope of Acetabularia and Batophora, a fibrillar reticulum is absent.     

Ultrastructural features of the life cycle ofAcetabularia mediterranea

Summary The portion of the life cycle ofAcetabularia mediterranea from cyst formation to gamete release is described. During maturation, the cyst nucleus undergoes a series of mitoses in which the nuclear membrane remains intact, and the spindle microtubules are confined to the intranuclear space. There is a dark requirement for the completion of cyst maturation at the end of which the nuclei are in groups and centrioles are present. The final migration of the nuclei, cleavage of the cytoplasm into gametes, and the development of flagella is cxtremely rapid, taking six to twelve hours. Cysts which fail to germinate are blocked at a late stage in the maturation process, either before or after the final nuclear division.The observations are related to mitosis in other green algae (Chlorophyceae) and to gametogenesis inBryopsis hypnoides. Changes in the amount and distribution of heterochromatin in the nuclei are discussed in relation to the life cycle ofA. mediterranea.The substance of this paper was first presented orally at the Symposium onAcetabularia held at the Max-Planck-Institut für Zellbiologie, Wilhelmshaven, Federal Republic of Germany, July 12–15th, 1972.Supported in part by Grant GM 06637 from the U.S. Public Health Service.     

The Bryopsis hypnoides plastid genome: multimeric forms and complete nucleotide sequence

Background

Bryopsis hypnoides Lamouroux is a siphonous green alga, and its extruded protoplasm can aggregate spontaneously in seawater and develop into mature individuals. The chloroplast of B. hypnoides is the biggest organelle in the cell and shows strong autonomy. To better understand this organelle, we sequenced and analyzed the chloroplast genome of this green alga.

Principal Findings

A total of 111 functional genes, including 69 potential protein-coding genes, 5 ribosomal RNA genes, and 37 tRNA genes were identified. The genome size (153,429 bp), arrangement, and inverted-repeat (IR)-lacking structure of the B. hypnoides chloroplast DNA (cpDNA) closely resembles that of Chlorella vulgaris. Furthermore, our cytogenomic investigations using pulsed-field gel electrophoresis (PFGE) and southern blotting methods showed that the B. hypnoides cpDNA had multimeric forms, including monomer, dimer, trimer, tetramer, and even higher multimers, which is similar to the higher order organization observed previously for higher plant cpDNA. The relative amounts of the four multimeric cpDNA forms were estimated to be about 1, 1/2, 1/4, and 1/8 based on molecular hybridization analysis. Phylogenetic analyses based on a concatenated alignment of chloroplast protein sequences suggested that B. hypnoides is sister to all Chlorophyceae and this placement received moderate support.

Conclusion

All of the results suggest that the autonomy of the chloroplasts of B. hypnoides has little to do with the size and gene content of the cpDNA, and the IR-lacking structure of the chloroplasts indirectly demonstrated that the multimeric molecules might result from the random cleavage and fusion of replication intermediates instead of recombinational events.     

INTRASPECIFIC INTERACTIONS AND PARASITISM IN AN ASSOCIATION OFRHIZOCARPON LECANORINUMandR. GEOGRAPHICUM

Intraspecific thallus interactions in mixed populations ofRhizocarpon lecanorinumR. geographicumin North Wales are described. In contrast to the most commonly occurring morphotype ofR. geographicumwhich forms mosaics comprised of sharply delimited individual thalli,R. lecanorinumthalli consistently merge with one another at intraspecific contacts, leaving no visible trace of their initial boundaries. On the analogy of mycelial interactions in populations of wood-rotting and other non-lichen-forming fungi, it is postulated that these differences are the outcome, inR. geographicumof somatic incompatibility between distinct genotypes, and inR. lecanorinumof somatic compatibility among genetically identical or very closely related thalli. Possible mechanisms for the evolution of clonal population structure inR. lecanorinumand links between somatic interactions and reproductive output in these species are discussed. Facultative parasitism ofR. lecanorinumbySchaereria fuscocinereaand resistance to such parasitism by co-occurringR. geographicumare also documented.     

WALL STRUCTURE AND LATERAL FORMATION IN THE ALGA BRYOPSIS

Green , Paul B. (U. Pennsylvania, Philadelphia.) Wall structure and lateral formation in the alga Bryopsis. Amer. Jour. Bot. 47(6) : 476–481. Illus. 1960.—The large multinucleate cells of Bryopsis pennata regularly produce laterals at the apical tip. Cells were freed of protoplasm and the remaining cell wall was flattened and studied in polarized light and interference microscopes. Both the cylindrical main axis and the cylindrical laterals are negatively birefringent and thus apparently have generally a transverse arrangement of microfibrils. Lateral formation is first seen in the formation of round fields of concentric microfibrils on the main axis which persist as lateral-bases. The center of a field protrudes, making a small out-pouching of the main axis. The thin-walled protrusion increases first mostly in diameter and then in length to make a lateral. There is a definite correlation between wall structure (optical anisotropy) and cell shape in Bryopsis.     

The role of microtubules in establishing nuclear spatial patterns in multinucleate green algae

Summary In uninucleate cells, cytokinesis follows karyokinesis, thereby reestablishing a specific nucleus-to-cytoplasm ratio. In multinucleate cells, cytokinesis is absent or infrequent; no plasmalemma boundary defines the cytoplasmic territory of an individual nucleus. Several genera of large multinucleate green algae were examined with epifluorescence light microscopy to determine whether the patterns of cytoplasmic organization establish nuclear cytoplasmic domains. Randomly spaced nuclei, singular mitotic events and cytoplasmic streaming characterize the organization of two genera,Derbesia andBryopsis (Caulerpales). The cells ofValonia, Valoniopsis, Boergesenia, Ventricaria (Siphonocladales), andHydrodictyon (Chlorococcales) display regularly spaced nuclei which undergo synchronous divisions in a stationary cytoplasm. In the cytoplasm of genera with regularly spaced nuclei, microtubules radiate from all nuclei in late telophase-early interphase. These internuclear microtubule arrays are not found in algal genera with randomly spaced nuclei. It is hypothesized that these microtubule arrays play a role in establishing the cytoplasmic domain of each nucleus in genera with regularly spaced nuclei. Loss of microtubule arrays during the events of mitosis correlated positively with the increasing randomization of nuclear patterns in algae grown in microtubule inhibitors. Cytoplasmic domains were maintained when cells were grown in the same media in the dark. This suggests that, after a round of division, regular nuclear spacing in certain multinucleate algae is reestablished by internuclear microtubule arrays, which are not, however, required to maintain spacing during interphase.Dedicated to the memory of Professor Oswald Kiermayer     

Wiedereinführung vonBryopsis lyngbyei (Bryopsidales,Chlorophyta) als selbständige Art

Zusammenfassung 1. Die bisher in der Algenflora Helgolands alsBryopsis plumosa (Huds.) C. Ag. geführte Art wurde alsBryopsis lyngbyei Hornemann erkannt.2. Der Umriß der dicht zweizeilig gefiederten Art ist einer Vogelfeder ähnlich.Bryopsis lyngbyei ist diözisch; ihr Lebenszyklus schließt ein fadenförmiges Sporophytenstadium ein, das nur stephanokonte Zoosporen erzeugt.3. Die negativen Kreuzungsversuche mit Herkünften vonBryopsis plumosa europäischer Küstenabschnitte erweisen die Selbständigkeit vonBryopsis lyngbyei.

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Reestablishment ofBryopsis lyngbyei (Bryopsidales, Chlorophyta) as separate species

This study investigates the taxonomic status of a Helgoland species hitherto regarded asBryopsis plumosa (Huds.)Ag. The habitus of the plant concerned agrees well with that of the original specimens ofBryopsis lyngbyei Hornemann in the Botanical Museum of Copenhagen. Pinnules arise distichously from the axis; the life cycle of the dioecious species includes a filamentous sporophytic stage which produces only stephanokontic zoids. Crosses with samples ofBryopsis plumosa from European coasts were unsuccessful; thusBryopsis lyngbyei is evidently a separate species.

     

Local accumulation of the cell content and growth

Summary The cell content (protoplasm, chloroplasts, nuclei) ofBryopsis andPseudobryopsis can be accumulated in the tips of the branches by different agents — as hypertonic solution, centrifugation, neutral red staining. When the plants are cultured in sea water in all these cases inflation of the tips, local growth or thickening of the cell wall follows. The reaction of the plant depends on inner physiological conditions and varies with age and nutrition.The centrifuged cells ofHydrodictyon are a proof that a polynuclear cell does not behave as a physiological unity; a unilateral amassing of plasma and nuclei causes a local growth of one part of the cell; the centrifugal part of the cell inflates and the cell assumes the shape of a club.The experiments onBryopsis andPseudobryopsis show that the different parts of the coeloblasts show a high degree of independence and can develop in a special manner.The experiments show the possibility of correlation between the concentration — the quantitative distribution — of the cell content and the growth or thickening of the cell membrane.Revision and experimental analysis of the term energide bySachs appear to be necessary from these points of view.     

PSEUDOBRYOPSIS MYURA AND ITS REPRODUCTION

Pseudobryopsis myura, type of the genus, is monoecious; male and female gametocysts occur on the same plant; there is definite anisogamy and only macrogametes possess a stigma. The mode of extrusion of the gametes differs both from the Bryopsis-type and from the Codium-type. As in Codium the discharge of the gametocyst is due to internal pressure. Gametes become motile only after their extrusion from the gametocyst.     

Leaf architecture of some acanthaceae

Leaf architectural pattern has been studied in 27 genera and 35 species of the Acanthaceae. The major venation pattern conforms to pinnate camptodromous with eucamptodromous or festooned brochidodromous secondaries, pinnate craspedodromous inAcanthus ilicifolius and acrodromous inLepidagathis trinervis. Intersecondary veins are common. The marginal ultimate venation is looped. The areoles are variable in size. The vein endings are usually simple, linear or cuved or divide once or twice dichotomously. Isolated vein endings, tracheids, isolated free vein endings and extension cells are observed. Transfusion tracheids are seen inDicliptera verticillata. Miniature vessel elements with simple perforation plates are noticed lying free in the areole or at the end of tracheids inSeriocalyx scaber andThunbergia grandiflora.Elytraria acaulis, Nelsonia canescens andStaurogynae zeylanica exhibit venation pattern shown by majority of the taxa studied, of the Acanthaceae.     

Larval development of a gobiid fish,Odontohutis obscura obscura in comparison with that ofO. o. interrupta and ofO. platycephala

Larval development ofOdontobutis obscura obscura, reared withArtemia sp. andLimnodrilus sp. for about two months, was observed in a room maintained at 20±0.5°C. The development was classified into nine nominal stages, and was compared with that ofO. o. interrupta and ofO. platycephala. The size and shape of the eggs and the development of this species are similar to those ofO. o. interrupta andO. platycephala. From the juvenile stage,O. obscura is distinguishable fromO. platycephala by the appearance of dark bands on the body located in the same position as in adults.O. o. interrupta is also distinguished fromO. o. obscura in the juvenile stage by the presence of melanophores on the dorsal and ventral sides of the caudal peduncle. The anal fin fold ofO. obscura is higher than the dorsal fin fold, but the two folds are equal in height inO. platycephala. O. obscura has a well-developed air bladder and swims high in the water at the feeding stage.O. platycephala has a poorly developed air bladder and swims on the bottom. Xanthophores are observed at an earlier stage and more strongly developed inO. obscura than inO. platycephala. Growth rate is faster inO. obscura than inO. platycephala. O. obscura spawns at a smaller body size thanO. platycephala. InO. o. obscura, the arrangement of cephalic pit organs is completed at 14 mm SL. InO. o. interrupta, this arrangement is completed at the same time or a little later than inO. o. obscura. The infraorbital and verticalantorbital pit lines ofO. platycephala, which are separated in the adults, are connected until the juveniles measure about 30 mm SL. These pit lines are connected even in the adults ofO. o. obscura andinterrupta. InO. platycephala, the sensory canals are first formed behind the eyes, then dorso-anterior to the eyes, then at the posterior edge of the preopercles and finally anterior to the eyes. Postocular canals begin to form in individuals more than 20 mm SL. All individuals ofO. o. interrupta more than 70 mm SL have postocular canals.O. o. obscura has no sensory canals throughout life. The differences in growth rate, body size at spawning, and the time of completion of the cephalic lateral line system suggest paedomorphosis in the three taxa studied here.     

The Nicotinic Acetylcholine Receptor Dα7 Is Required for an Escape Behavior inDrosophila

Acetylcholine is the major excitatory neurotransmitter in the central nervous system of insects. Mutant analysis of the Dα7 nicotinic acetylcholine receptor (nAChR) ofDrosophila shows that it is required for the giant fiber-mediated escape behavior. The Dα7 protein is enriched in the dendrites of the giant fiber, and electrophysiological analysis of the giant fiber circuit showed that sensory input to the giant fiber is disrupted, as is transmission at an identified cholinergic synapse between the peripherally synapsing interneuron and the dorsal lateral muscle motor neuron. Moreover, we found thatgfA¹, a mutation identified in a screen for giant fiber defects more than twenty years ago, is an allele ofDα7. Therefore, a combination of behavioral, electrophysiological, anatomical, and genetic data indicate an essential role for the Dα7 nAChR in giant fiber-mediated escape inDrosophila.     

Parallel inductive kinetics of fluorescence and photoacoustic signal in dark-adapted thalli of Bryopsis maxima

The inductive kinetics of fluorescence and photoacoustic signal were measured simultaneously in dark-adapted thalli of the green coenocytic alga Bryopsis maxima. Under illumination with weak red light modulated at 60 Hz, the fluorescence yield varied, showing three maxima P, M₁ and M₂ almost immediately, 10 s and 6 min after the onset of the illumination, respectively (Yamagishi, A., Satoh, K. and Katoh, S. (1978) Plant Cell Physiol. 19, 17–25). The photoacoustic signal also showed inductive transients which parallel well those of the fluorescence up to the M₂ stage. After M₂, the photoacoustic signal remained at a constant level, while the emission yield gradually decreased. The first peak of the fluorescence induction and a corresponding peak of the photoacoustic transients were selectively eliminated by prior illumination or methyl viologen treatment of the dark-adapted thalli. The second peaks of the two induction curves were abolished by carbonylcyanide-m-chlorophenylhydrazone, whereas dicyclohexylcarbodiimide enhanced their peak heights and suppressed the subsequent decreases. The results indicate that the fluorescence yield is mainly determined by the redox state of the Photosystem II reaction center throughout the induction period except the last phase. Mechanisms underlying inductive transients of fluorescence are discussed in the light of the present findings.     

The occurrence of multinucleate giant cells in yeasts

Summary The spontaneous occurrence of giant cells has been observed in young cultures ofLipomyces lipofer and three different genotypes ofSaccharomyces. Stained preparations of all abnormal cultures revealed that the giant cells characteristically contained more than one nucleus, the number ranging from one to six. In both genera the phenomenon was found to be transient, for rapidlygrowing cultures arising from isolated giant cells reverted, at varying rates, to populations of small uninucleate cells which appeared normal in all respects.     

SURVIVING PROTOPLASTS IN VITRO AND THEIR DEVELOPMENT IN BRYOPSIS1

In the coenocytic marine alga Bryopsis plumosa, extracellular protoplasts synthesize new cell walls in vitro and can develop into normal pinnate plants in the same way of the zygote of this species.     

Dormancy in bulbils of several herbaceous plants: Effects of photoperiod,light, temperature,oxygen and gibberellic acid

Effects of some environmental conditions (photoperiod, white and colored lights, temperature, partial oxygen pressure) and growth regulators (gibberellic acid, 2-chloroethyltrimethylammonium chloride) on induction and release of dormancy of the bulbils ofDioscorea batalas, Laportea bulbifera, Elatostema involucratum andSedum bulbiferum were investigated. Bulbils were formed under short-day conditions inLaportea andElatostema, under long-day conditions inSedum, and irrespective of photoperiods inDioscorea. In all species exceptSedum, immature bulbils required light, particularly blue or far red, for sprouting (photo-sprouting stage), and mature bulbils required a cold treatment (thermo-sprouting stage). The duration of photo-sprouting and thermo-sprouting stages and the degree of dependency on light or low temperature of sprouting differed from species to species. Sprouting of chilled mature bulbils of these species was promoted by light, especially by red or green light. Both immature and mature bulbils ofSedum sprouted under short-day conditions. Continuous irradiation with blue, far-red and green light markedly inhibited their sprouting. Oxygen at high concentration inhibited the sprouting of immature bulbils inDioscorea; in the other species it promoted sprouting regardless of the maturation of the bulbils. Applications of gibberellic acid caused the sprouting of bulbils the absence of light, chilling or photoperiodic treatment in all species exceptDioscorea, in which gibberellic acid inhibited sprouting. Polyphenol oxidase activity was very high in the homogenates ofDioscorea bulbils, and increased further when the bulbils had been treated with gibberellic acid. In the other species, little or no such activity was observed.     

Fine structure of acrosome biogenesis and of mature sperm in the bivalve molluscs<Emphasis Type="Italic"> Glycymeris</Emphasis> sp. (Pteriomorphia) and<Emphasis Type="Italic"> Eurhomalea rufa</Emphasis> (Heterodonta)

Proacrosomal vesicles form during the pachytene stage, being synthetized by the Golgi complex in Glycymeris sp., and by both the Golgi and the rough endoplasmic reticulum in Eurhomalea rufa. During early spermiogenesis, a single acrosomal vesicle forms and its apex becomes linked to the plasma membrane while it migrates. In Glycymeris sp., the acrosomal vesicle then turns cap-shaped (1.8 μm) and acquires a complex substructure. In E. rufa, proacrosomal vesicles differentiate their contents while still at the premeiotic stage; as the acrosomal vesicle matures and its contents further differentiate, it elongates and becomes longer than the nucleus (3.2 μm), while the subacrosomal space develops a perforatorium. Before condensation, chromatin turns fibrillar in Glycymeris sp., whereas it acquires a cordonal pattern in E. rufa. Accordingly, the sperm nucleus of Glycymeris sp. is conical and elongated (8.3 μm), and that of E. rufa is short and ovoid (1.1 μm). In the midpiece (Glycymeris sp.: 1.1 μm; E. rufa: 0.8 μm), both species have four mitochondria encircling two linked orthogonal (Glycymeris sp.) or orthogonal and tilted (30–40°; E. rufa) centrioles. In comparison with other Arcoida species, sperm of Glycymeris sp. appear distinct due to the presence of an elongated nucleus, a highly differentiated acrosome, and four instead of five mitochondria. The same occurs with E. rufa regarding other Veneracea species, with the acrosome of the mature sperm strongly resembling that of the recent Mytilinae. Electronic Publication     

THE IDENTITY OF PHOTOBIONTS FROM THE LICHENPYRENULA JAPONICA

Nine specimens ofPyrenula japonicaKurokawa were collected from various areas in Japan. Photobionts were isolated from their thalli and studied taxonomically. As a result, only one species of green alga,Trentepohlia lagenifera(Hild.) Wille was identified as the photobiont ofPyrenula japonica. This is the first record of this alga from the lichen genusPyrenula.     

Permanent residents or temporary lodgers: characterizing intracellular bacterial communities in the siphonous green alga Bryopsis

The ecological success of giant celled, siphonous green algae in coastal habitats has repeatedly been linked to endophytic bacteria living within the cytoplasm of the hosts. Yet, very little is known about the relative importance of evolutionary and ecological factors controlling the intracellular bacterial flora of these seaweeds. Using the marine alga Bryopsis (Bryopsidales, Chlorophyta) as a model, we explore the diversity of the intracellular bacterial communities and investigate whether their composition is controlled by ecological and biogeographic factors rather than the evolutionary history of the host. Using a combination of 16S rDNA clone libraries and denaturing gradient gel electrophoresis analyses, we show that Bryopsis harbours a mixture of relatively few but phylogenetically diverse bacterial species. Variation partitioning analyses show a strong impact of local environmental factors on the presence of Rickettsia and Mycoplasma in their association with Bryopsis. The presence of Flavobacteriaceae and Bacteroidetes, on the other hand, reflects a predominant imprint of host evolutionary history, suggesting that these bacteria are more specialized in their association. The results highlight the importance of interpreting the presence of individual bacterial phylotypes in the light of ecological and evolutionary principles such as phylogenetic niche conservatism to understand complex endobiotic communities and the parameters shaping them.