Isolation and Characterization of a Sex-Specific Lectin in a Marine Red Alga,Aglaothamnion oosumiense Itono

In red algae, spermatial binding to female trichogynes is mediated by a lectin-carbohydrate complementary system. Aglaothamnion oosumiense is a microscopic filamentous red alga. The gamete recognition and binding occur at the surface of the hairlike trichogyne on the female carpogonium. Male spermatia are nonmotile. Previous studies suggested the presence of a lectin responsible for gamete recognition on the surface of female trychogynes. A novel N-acetyl-d-galactosamine-specific protein was isolated from female plants of A. oosumiense by affinity chromatography and named AOL1. The lectin was monomeric and did not agglutinate horse blood or human erythrocytes. The N-terminal amino acid sequence of the protein was analyzed, and degenerate primers were designed. A full-length cDNA encoding the lectin was obtained using rapid amplification of cDNA ends-PCR (RACE-PCR). The cDNA was 1,095 bp in length and coded for a protein of 259 amino acids with a deduced molecular mass of 21.4 kDa, which agreed well with the protein data. PCR analysis using genomic DNA showed that both male and female plants have this gene. However, Northern blotting and two-dimensional electrophoresis showed that this protein was expressed 12 to 15 times more in female plants. The lectin inhibited spermatial binding to the trichogynes when preincubated with spermatia, suggesting its involvement in gamete binding.     

Cell-Cell Recognition during Fertilization in a Red Alga, Antithamnion sparsum (Ceramiaceae, Rhodophyta)

A gamete recognition mechanism in Antithamnion sparsum Tokidais proposed based on experiments using various lectins and carbohydrates.Spermatial binding to trichogynes is inhibited by pre-incubationof spermatia with concanavalin A (ConA) and/or L-fucose, whiletrichogyne receptors are blocked by the complementary carbohydrate-methyl D-mannose and/or the lectin Ulex europaeus agglutinin(UeA1). Binding inhibition (40–50%) was observed with10–50 mM carbohydrates and 25–50 µg ml^-1 lectins.The inhibitory effects of ConA and UeA1 is partially reversed(to 80–90% of controls) by addition of -methyl D-mannoseand L-fucose, respectively. Lectin binding to spermatial surfaceswas visualized by Fluorescein isothiocyanate (FITC) conjugatedConA, whereas carbohydrate receptors along the trichogyne andspermatium were localized with -mannosylated-FITC-albumin andL-fucosylated-FITC-albumin, respectively. These results suggestthat gamete recognition in Antithamnion sparsum is mediatedby a double-docking recognition system consisting of spermatiapossessing surface L-fucose receptors and -methyl D-mannosemoiety, and trichogynes possessing the complementary receptors. (Received December 5, 1995; Accepted April 22, 1996)     

140 Ecophysiology of The Red Alga Porphyra Umbilicalis Kützing (Rhodophyta,Bangalies): Responses to Abiotic Stress

The effects of tidal elevation, emersion, sun exposure, and season on several antioxidant enzymes (ascorbate peroxidase, glutathione reductase, and catalase), pigments (phycoerythrin, phycocyanin, chlorophyll a and total carotene) and photosynthetic efficiency of photosystem II (Fv/Fm) in Porphyra umbilicalis were evaluated. Plants were collected monthly from sun‐exposed and shaded locations in the high, mid, and low intertidal following periods of tidal emersion ranging from 0–6 hours. Glutathione reductase activity was greatly affected by emersion during summer months, while ascorbate peroxidase and catalase activities showed no seasonal patterns. Differences in glutathione reductase and catalase levels occurred between sun‐exposed and shaded plants in the high and mid intertidal during summer. At all elevations, photosynthetic pigments showed a strong seasonal trend, with the effect of sun exposure being most apparent during summer. While total carotene increased with emersion during summer months, the combined effects of emersion and season were inconsistent for phycoerythrin, phycocyanin and chl a. Photosynthetic efficiency (Fv/Fm) decreased following emersion in summer and fall. During most months, sun exposed plants had lower Fv/Fm values compared to plants growing in the shade. This study emphasizes the importance of examining the effects of abiotic stresses simultaneously in order to reveal interactive relationships.     

Karyology and sex determination in Aglaothamnion oosumiense Itono (Ceramiaceae,Rhodophyta)

A cytogenetic investigation on male and female reproductive cells of Aglaothamnion oosumiense Itono indicates that the sexuality of this species might be determined by a sex chromosome. Chromosome counts in female and male gametophytes gave 37 and 36, respectively. Sex ratio of gametophytes was 1:1. Both male-derived and female-derived bisexual plants were observed. Bisexual plants were different in gross morphology and position of carpogonial branches from normal unisexual gametophytes. The chromosome number of female-derived bisexual plants was N=37 and male-derived bisexual plants was N=36. Some male plants developed parasporangia in addition. The paraspore germlings showed the same chromosome number as the male plants. The fertilized carpogonium and gonimoblast cells had 2N = ca. 70 chromosomes.     

Ultrastructure of Carposporogenesis in the Red Alga Caulacanthus ustulatus (Gigartinales, Caulacanthaceae)

Carposporangium differentiation in Caulacanthus ustulatus (Turner)Ktzing proceeds through four developmental stages. The youngestcarposporangia are embedded within confluent mucilage and containa nucleus, a few small starch granules, concentric membranebodies and proplastids without a peripheral thylakoid. The intermediate-agedcarposporangia are characterized by the formation of fibrousvacuoles by a fibrous vacuole associated organelle (FVAO). Plastidsalso start to develop their internal thylakoid system. In nearlymature carposporangia, highly active, curved dictyosomes producecored vesicles, while fibrous vacuoles increase in number anddisplay a perinuclear arrangement. Abundant starch granulesare present, some of which exhibit a degenerating appearance.A carposporangium wall is formed and plastids complete theirinternal thylakoid system. Carposporangium maturation is signalledby the presence of adhesive vesicles. Fully developed and peripherallyarranged plastids, centrally located fibrous vacuoles, fewerstarch granules and a monolayered wall are the features of maturecarposporangia. Carposporogenesis, Caulacanthus ustulatus (Turner) Kützing, red algae, ultrastructure     

Complementary Association of an Endophytic Red Alga and a Shell-encrusting Green Alga

Endophytic filaments of a red alga in the shell-encrusting greenalga Pseudulvella consociata S. & G. collected from subtidaland intertidal habitats in the San Juan Islands, WashingtonState, U.S.A., have been identified as Audouinella sparsa (Harvey)Dixon. The association appears to be complementary. Pseudulvella consociata, Audouinella sparsa, alage, Rhodophyta, Chlorophyta, endophyte     

Purification and Characterization of Mannitol-l-Phosphatase in the Red Alga Caloglossa continua (Ceramiales, Rhodophyta)

Purification of mannitol-l-phosphatase, an enzyme catalyzing the final step of mannitol biosynthesis, was first achieved in the mannitol-accumulating red alga Caloglossa continua (Okamura) King et Puttock. The enzyme was shown to be a monomer, since gel filtration and sodium dodecyl sulfate–polyacrylamide gel electrophoresis gave close values of apparent molecular weights of 28,500 and 30,200, respectively. The protein exhibited an isoelectric point of 4.8. The substrate specificity for mannitol-l-phosphate (MIP) was very high, and that for K _m(MIP) was 0.41 mM. The catalytic activity was optimal at pH 7.4. The enzyme was activated by Mg²⁺, but was strongly inhibited by Ca²⁺, NaF, N-ethylmaleimide, and p-hydroxymercuribenzoic acid. Seawater levels of NaCl and physiological levels of mannitol also inhibited the activity by 50% or more. Changes in the concentrations of those ions and metabolites may regulate the biosynthesis of mannitol as an osmoregulant in vivo. Received May 7, 2001; accepted June 15, 2001.     

Floridoside,L-Isofloridoside,and D-Isofloridoside in the Red Alga Porphyra columbina (Seasonal and Osmotic Effects)

The quantitative heteroside distribution in Porphyra columbina Montagne and Bangia atropurpurea (Roth) C. Agardh (Bangiales, Rhodophyta) has been measured using 13C-nuclear magnetic resonance spectroscopy and gas-liquid chromatography. In P. columbina, floridoside and both D- and L-isofloridoside were recorded, with concentrations of L-isofloridoside exceeding those of floridoside. All three compounds were also measured in B. atropurpurea. Marked changes in the relative amounts of the heterosides were recorded throughout the season. The role of L-isofloridoside in the osmotic acclimation of P. columbina has been demonstrated.     

Identification of Calmodulin in the Red Alga Susabi Laver (Porphyra yezoensis)

To test whether calmodulin is present in the red alga Susabi laver (Porphyra yezoensis), materials was concentrated from this alga, using hydrophobic chromatography. In this case, 0.25 m (NH₄)₂SO₄ should be added to bind the protein to the column in the presence of 5 mm CaCl₂. Calmodulin is present in the marine red alga, although at a very low concentration.     

The First Symbiont-Free Genome Sequence of Marine Red Alga,Susabi-nori (Pyropia yezoensis)

Nori, a marine red alga, is one of the most profitable mariculture crops in the world. However, the biological properties of this macroalga are poorly understood at the molecular level. In this study, we determined the draft genome sequence of susabi-nori (Pyropia yezoensis) using next-generation sequencing platforms. For sequencing, thalli of P. yezoensis were washed to remove bacteria attached on the cell surface and enzymatically prepared as purified protoplasts. The assembled contig size of the P. yezoensis nuclear genome was approximately 43 megabases (Mb), which is an order of magnitude smaller than the previously estimated genome size. A total of 10,327 gene models were predicted and about 60% of the genes validated lack introns and the other genes have shorter introns compared to large-genome algae, which is consistent with the compact size of the P. yezoensis genome. A sequence homology search showed that 3,611 genes (35%) are functionally unknown and only 2,069 gene groups are in common with those of the unicellular red alga, Cyanidioschyzon merolae. As color trait determinants of red algae, light-harvesting genes involved in the phycobilisome were predicted from the P. yezoensis nuclear genome. In particular, we found a second homolog of phycobilisome-degradation gene, which is usually chloroplast-encoded, possibly providing a novel target for color fading of susabi-nori in aquaculture. These findings shed light on unexplained features of macroalgal genes and genomes, and suggest that the genome of P. yezoensis is a promising model genome of marine red algae.     

Isolation,Growth, Ultrastructure,and Metal Tolerance of the Green Alga,Chlamydomonas acidophila (Chlorophyta)

An acidophilic volvocine flagellate, Chlamydomonas acidophila (Volvocales) that was isolated from an acid lake, Katanuma, in Miyagi prefecture, Japan was studied for growth, ultrastructural characterization, and metal tolerance.

Chlamydomonas acidophila is obligately photoautotrophic, and did not grow in the cultures containing acetate or citrate even in the light. The optimum pH for growth was 3.5-4.5. To characterize metal tolerance, the toxic effects of Cd, Co, Cu, and Zn on this alga were also studied. Effective metal concentrations, which limited the growth by 50%, EC₅₀ were measured, after 72h of static exposure. EC₅₀s were 14.4 μM Cd²⁺, 81.3 μM Co²⁺, 141μM Cu²⁺, and 1.16 mM Zn²⁺ for 72 h of exposure. Thus, this alga had stronger tolerance to these metals than other species in the genus Chlamydomonas.     

Protochlorophyll(ide) in a Blue-Green Alga

During growth under far-red (>650 nm) light, Anacystis nidulans accumulates protochlorophyllide to concentrations about one-tenth of the chlorophyll. From whole cell fluorescence spectra, protochlorophyll(ide) was identified also in another blue-green, and in a red, alga grown in far-red light.     

Isolation, characterization and transposition of an (IS2)2 intermediate

We have isolated and characterized a dimer derivative of the extensively studiedEscherichia coli insertion sequence IS2. The dimer structure — called (IS2)₂ — consists of two IS2 elements arranged as a direct repeat, separated by 1 bp. The junction between the (IS2)₂ dimer and target sequences is located at various positions in independent isolates; however, one position was preferred. The transposition of (IS2)₂ into a target plasmid resulted in cointegrate-type structures. The transposition frequency of the (IS2)₂ dimer itself was significantly higher than that of the isogenic monomer IS2 insertion. The poor stability and high activity of (IS2)₂ indicates that this is an active transposition intermediate. The mode of transposition of (IS2)₂ is analogous to the joined dimer model described in the case of (IS21)₂ and (IS30)₂.     

Bromine, Bromophenols and Floridorubin in the Red Alga Lenormandia prolifera

The pigment floridorunin was localized to the cuticle of the red alga Lenormandia prolifera (C. Ag.) J. Agardh by x-ray micro-analysis in Ihe transmission electron microscope and by its colour reactions in the light microscope. The pigment was set free from the cell wall by a pectinase. Bromine was also identified in the chloro-plasts. the middle lamellae, the intercellulars and the pore plugs of the alga. The content of bromophenols in the alga increases with increasing age. The cell walls of old plants are stratified and their outer parts are apparently shed. The bromophenols could have a function as regulators of the epiphytes or the shedding of parts of the outer cell wall.     

An Investigation of Tetrasporogenesis in the Marine Red Alga Gastroclonium clavatum (Roth) Ardissone (Rhodymeniales)

Gastroclonium clavatum tetrasporogenesis have been studied usinglight and electron microscopy. They are spherical bodies whichdifferentiate early and 50–70 per branch segment havebeen recorded. The developing sporangia expand into the largethallus cavity. The plastids become dispersed evenly throughthe cytoplasm at this stage. Thylakoids become arranged as parallelarrays and sporadically a single peripheral thylakoid enclosesall the others; the matrices contain globules reaching a maximumdiameter of 270 nm. Plastid multiplication occurs through binaryor multiple fission. The starch occurs in bowl-shaped grains.The mitochondria are always rich in cristae and often providedwith small opaque inclusions. The Golgi apparatus is markedby pleomorphic dictyosome features. Dictyosome-mitochondrionassociations are frequent. The different kinds of cytoplasmicinclusion are described. Gastroclonium clavatum, Rhodophyta, tetrasporogenesis, ultrastructure     

The Ultrastructure of Tetrasporogenesis in the Marine Red Alga Chondria tenuissima (Good, et Woodw.) (Ceramiales, Rhodomelaceae)

Tetraspore development has been studied in Chondria tenuissimausing light and electron microscopy. The transformation of tetrasporangialmother cells into mature tetrasporangia involves a series ofstructural changes, especially of dictyosomes and of the nucleus.The youngest stage of tetrasporogenesis consists of a uninucleatetetraspore mother cell with synaptonemal complexes present duringearly prophase of meiosis I. Mitochondria are aggregated aroundthe nucleus, dictyosome activity is low, and proplastids occurin the peripheral cytoplasm. The cleavage furrows are initiatedalmost concomitantly with commencement of meiosis. When thecleavage furrows are initiated, spherical bodies bounded bytwo membranes are found within the cytoplasm; they develop intovacuoles with fibrillar contents (fv₁), which increase in sizeduring tetraspore development by fusing with each other andwith Golgi vesicles. The Golgi vesicles and the vacuoles withfibrillar contents (fv₁) contribute material to the developingtetraspore wall. During the middle stage of tetraspore formationthe vacuoles with fibrillar contents (fv₁) are dominant, dictyosomeactivity increases, as well as the number of plastids and mitochondria;starch formation also increases. Stacked cisternae of the endoplasmicreticulum are found within the peripheral part of the nucleus.The same nuclear structures are also observed in tetrasporangiaof the marine red alga Gastroclonium clavalum. The final stageis characterized by the disappearance of vacuoles with fibrillarcontents (fv₁) and of the stacked ER within the nucleus, presenceof straight, large dictyosomes which produce cored vesicles,an abundance of starch grains and by the formation of fullydeveloped chlorqplasts. The cored vesicles contain Thiéry-positivematerial and contribute to the formation of vacuoles with fibrouscontents (fv₂) as they are dominant in the tetraspores beforetheir liberation. Rhodophlyla, Chondria, tetrasporogenesis, ultrastructure, Golgi apparatus     

Isolation, X-ray single crystal and theoretical study of quinquevalent metal oxoisopropoxides, Nb6O8(PrO)14(PrOH)2 and Re4O6(OPr)10

Oxoisopropoxide complexes of niobium, Nb₆O₈(ⁱPrO)₁₄(ⁱPrOH)₂ (I), and rhenium, Re₄O₆(OⁱPr)₁₀ (II), were isolated as byproducts of anodic oxidation of these metals in ⁱPrOH in the presence of LiCl as conductive additive. The common feature of both structures consists in the occurrence in their molecules of an M₄O₁₆ planar core formed in the formal absence of M-M bonding for I and in the presence of electron-deficient but surprisingly short (Re-Re 2.52-2.54 Å) metal-metal bonds in II. The stability of this core for the oxoalkoxide derivatives of rhenium(V,VI) and niobium(V) and poor stability for those of tantalum(V) are discussed based on the results of quantum-chemical calculations.