DEVELOPMENTAL STUDIES IN PORPHYRA (RHODOPHYCEAE). III. EFFECT OF CULTURE CONDITIONS ON WALL REGENERATION AND DIFFERENTIATION OF PROTOPLASTS1

Protoplasts isolated from thalli of four Porphyra species regenerated successfully into differentiated plantlets. The efficiency of protoplast isolation and the developmental patterns of the regenerating protoplasts depended on the type of tissues from which they were isolated. However, culture conditions greatly influenced the patterns of development at the cellular and organismal levels. Sorbitol, nitrogen, and agar concentration in the medium controlled rates of cell division, thickening of cell walls, development of rhizoids, and formation of calluses or differentiated blades. Agitation disturbed the attachment of the protoplasts to a substrate. Cells in agitated cultures produced suspensions of single cells and non-polarized small calluses. Calluses which developed from protoplasts survived in storage for over two years. The stored calluses, and cells and protoplasts that were isolated from them, were subcultured successfully. We forsee extensive use of Porphyra cell suspensions for strain selection and vegetative propagation of cultivars. This technology, which makes vegetative cloning of selected Porphyra plants possible, may eliminate the need for cultivation and storage of the conchocelis phase. Protoplasts are also being used as tools for studies in genetic engineering of these commercial species.     

DEVELOPMENTAL STUDIES IN PORPHYRA (BANGIOPHYCEAE). II. CHARACTERIZATIO OF THE MAJOR LECTIN BINDING GLYCOPROTEINS IN DIFFERENTIATED REGIONS OF THE PORPHYRA PERFORATA THALLUS1

Detergent soluble extracts of differentiated regions of the Porphyra perforata J. Ag. thallus (holdfast, rhizoidal, vegetative and reproductive cells) were fractionated on sodium dodecyl sulfate polyacrylamide gels. Glycoproteins were identified by their lectin affinity. Extracts from all areas of the thallus contained glycoproteins, but the staining patterns were different for each region with each of the lectins tested: concanavalin A, Ulex europeaus agglutinin, Ricinus communis agglutinin, soybean agglutinin and peanut agglutinin. These data indicate that the morphologically distinct regions of the thallus also differ biochemically. Analysis of the lectin blots revealed the presence of tissue-specific glycoproteins in the five thallus areas. Such unique glycoproteins could be used as markers of differentiation in this species.     

克鲁维酵母高渗培养与原生质体制备与再生

研究了高渗预培养条件对克鲁维酵母Ｙ０３４原生质体形成与再生的影响。结果表明,同等条件下,经高渗预培养的原生质体再生率为常规培养的１．７倍,为改造菌株遗传特性而制备高活性原生质体探索了新的途径。     

MEIOSIS,BLADE DEVELOPMENT,AND SEX DETERMINATION IN PORPHYRA PURPUREA (RHODOPHYTA)1

The discovery in the early 1980s that meiosis occurs during germination of conchospores of Porphyra yezoensis Ueda suggested that the sexually divided fronds of Porphyra purpurea (Roth) C. Agardh might similarly originate from meiotic segregation of a pair of sex-determining alleles during early sporeling development. After establishing conditions suitable for propagating P. purpurea in culture, observations on developing sporelings demonstrated that meiosis takes place during the first two divisions of the germinating conchospores. In the first division, the spore is split into an upper and lower cell. In the second, an anticlinal division in the upper cell yields two daughter cells situated one beside the other, and a periclinal division in the bottom cell gives two cells arranged one above the other. Thus, during normal development, the first four cells of the sporeling constitute a meiotic tetrad whose cells are arranged in a characteristic fashion. Stable color mutants of P. purpurea were isolated, genetically characterized, and used as genetic markers to follow the fate of individual cells of the tetrad during subsequent frond development. Nearly the entire blade of the mature thallus is derived from the two upper cells of the tetrad, with the two lower cells mostly giving rise to the rhizoidal holdfast region. Cell lineage boundaries laid down by the segregation of color alleles at meiosis corresponded perfectly with those later defined by sexual differentiation on the same fronds, strongly supporting the hypothesis that sex determination in P. purpurea is controlled by alleles at a segregating chromosomal locus.     

REGENERATION AND SEXUAL DIFFERENTIATION OF GRIFFITHSIA JAPONICA (CERAMIACEAE,RHODOPHYTA) THROUGH SOMATIC CELL FUSION1

Hybrid cells were obtained from somatic cell fusion among male, female, and tetrasporangial plants in Griffithsia japonica Okamura by a wound-healing process. Isolated fusion cells regenerated new mature plants with mixed reproductive structures. The plants regenerated from hybrid cells between male and female plants developed into 1) spermatangiate, 2) carpogonial, 3) bisexual with spermatangia and carpogonial branches, 4) mixed-phase with spermatangia and tetrasporangia, or 5) bisexual/mixed-phase plants with spermatangia, carpogonial branches, and tetrasporangia. About 70% of the plants regenerated from hybrid cells between male and female plants produced tetrasporangia that were always formed with spermatangia on a single cell. Some of those tetrasporangia released tetraspores, six of which gave rise to mature plants. The plants regenerated from hybrid cells between male and tetrasporangial plants developed into spermatangiate, tetrasporangiate, or mixed-phase plants with spermatangia and tetrasporangia. The plants regenerated from hybrid cells between female and tetrasporangial plants developed into carpogonial, tetrasporangiate, or mixed-phase plants with carpogonial branches and tetrasporangia. All types of reproductive structures we re functional.     

STRUCTURE,LIFE HISTORY AND SYSTEMATICS OF RHOICOSPHENIA (BACILLARIOPHYTA). IV. CORRELATION OF SIZE REDUCTION WITH CHANGES IN VALVE MORPHOLOGY OF RH. GENUFLEXA1

Rhoicosphenia Grun. is a relatively isolated genus among the biraphid diatoms. Morphological changes in an isopolar member of the genus, Rh. genuflexa (Kütz.) Medlin, were investigated using light and scanning electron microscopy. The fully raphid valve showed changes in its flexure that could be correlated with size reduction during its life history from the initial cells to the smallest cells found in the population. Bands showed changes in number (from three to one) related to size reduction. Rh. genuflexa is morphologically similar to Rh. abbreviata (C. Ag.) Lange-Bert. (=Rh. curvata (Kütz.) Grun.), although the two are distinct taxa. These observations support previous contentions that Rhoicosphenia is a natural taxonomic grouping.     

SILICEOUS SCALE PRODUCTION IN CHRYSOPHYTE AND SYNUROPHYTE ALGAE. I. EFFECTS OF SILICA-LIMITED GROWTH ON CELL SILICA CONTENT,SCALE MORPHOLOGY,AND THE CONSTRUCTION OF THE SCALE LAYER OF SYNURA PETERSENII1

The cells of synurophyte flagellates (algal class Synurophyceae, formerly included in the Chrysophyceae) are enclosed within a regularly imbricate layer of ornamented siliceous scales. Scale morphology is of critical taxonomic importance within this group of algae, and the scales are valuable indicator microfossils in paleolimnological studies. The data presented here demonstrate that scale morphology and the integrity of the scale layer can exhibit extreme variability in culture as a function of the cellular quota of silica under silica-limited growth. Silica-limited, steady-state populations of the colonial flagellate Synura petersenii Korsh. were maintained over a range of specific growth rates (μ= 0.11–0.69 days^?1) and silica cell quotas (Q_si= 0.13–2.40 pmoles Si · cell¹). Scale morphology and the organization of the scale layer became increasingly aberrant as silica stress increased. Under severe stress, scale deposition was completely suppressed so that cells appeared scale-free. This depression of scale deposition was reversible; populations of silica-starved, scale-free cells rapidly regenerated new scale layers when placed in batch culture and spiked with dissolved silica. During recovery from silica stress, cell division was repressed for 24 h while mean cell silica quota increased 25-fold. The first new scales appeared within 2 h after the silica addition, and development of the new scale layer proceeded in an approximately synchronous manner, residting in normal scale layers on virtually all cells after 48 h of recovery in Sirich medium. Silica content of silica-replete Synura cells is comparable to freshwater diatoms of siynilar size, but Synura has much greater potential quota variability than diatoms and no apparent threshold silica requirement. Silica-limited growth kinetics and competition between diatoms and Synura for silica are discussed. The results suggest that morphological variability of siliceous scales in natural populations of synurophyte flagellates may result from silica stress and that the experimental approach developed here has great potential value as a means for circumscribing ecotypic variation in scale morphology. Results also demonstrate that scale production can be uncoupled from cell division, suggesting that cell cycle regulation of silica biomineralization in the Synurophyceae may be fundamentally different from that of diatoms (algal class Bacillariophyceae). This experimental system has application in the future study of the intracellular membrane systems and the regulatory processes involved in silica biomineralization.