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SUMMARY I studied the flagellar movements and mating behavior of biflagellate gametes produced by the green marine macroalga Bryopsis maxima using high‐speed video microscopy. This procedure allowed me to visualize the very rapid fertilization process in a marine ulvophycean. Discharged male and female gametes always swung their flagella backwards during forward swimming. They swam with a flagellar beat type pattern in which undulatory waves produced at the flagellar bases propagated towards the tips. Each beat cycle lasted 15–20 ms. Male gametes were immediately attracted to the vicinity of female gametes when the two mating types were mixed. As each male gamete swam past a female, it reversed direction towards the female by changing the beat pattern of one of its two flagella. The attraction of male gametes to the female ones was inhibited in calcium‐free seawater in both the presence and absence of 10 mM ethylene glycol‐bis(β‐aminoethyl ether)‐N,N,N′,N′‐tetraacetic acid, a calcium chelator, but attraction recovered in the presence of 10 mM CaCl2, suggesting that Ca2+ is necessary for the attraction response. The initial contact between the two gametes occurred when one of the male flagellar tips encountered a female flagellum. The male gamete kept in contact with the female gamete (i) at the flagellar tips, and then (ii) by anterior cell body contact. Flagella continued to beat and cell bodies oscillated as gametes maintained contact. In the final step, the gametes fused. [ABSTRACT FROM AUTHOR]

Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of I, Cs, Cs, and Ba as fission products of U. Interestingly, B. maxima contained naturally occurring radionuclides derived from Ra and Ra. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive Sr incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the Sr was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that Sr radioactivity was permeable through a dialysis membrane, the Sr was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70 % of the Sr did not precipitate as SrSO, indicating that a proportion of the Sr may bind with small molecules in B. maxima. [ABSTRACT FROM AUTHOR]

After mechanical wounding of the marine green alga Bryopsis maxima in a phosphate buffer, one main organic component was released to the solution. The organic compound was characterized by a molecular ion at 238 m/z by gas chromatography–mass spectrometry (GC-MS) and was deduced as 8-heptadecene by the fragment pattern. To identify the stereochemistry of 8-heptadecene, synthetic ( Z/ E)-8-heptadecene was coinjected to the solution of wounded B. maxima. Comparing retention times and mass spectra with the synthetic sample, the target hydrocarbon obtained from wounded B. maxima was coincident with ( Z)-8-heptadecene. [ABSTRACT FROM AUTHOR]

The stoichiometry and antenna sizes of the two photosystems in two marine green algae, Bryopsis maxima and Ulva pertusa, were investigated to examine whether the photosynthetic apparatus of the algae can be related to the light environment of their natural habitat. Bryopsis maxima and Ulva pertusa had chlorophyll (Chl) a/b ratios of 1.5 and 1.8, respectively, indicating large levels of Chl b, which absorbs blue-green light, relative to Chl a. The level of photosystem (PS) II was equivalent to that of PS I in Bryopsis maxima but lower than that of PS I in Ulva pertusa. Analysis of QA photoreduction and P-700 photo-oxidation with green light revealed that >50% of PS II centres are non-functional in electron transport. Thus, the ratio of the functional PS II to PS I is only 0.46 in Bryopsis maxima and 0.35 in Ulva pertusa. Light-response curves of electron transport also provided evidence that PS I had a larger light-harvesting capacity than did the functional PS II. Thus, there was a large imbalance in the light absorption between the two photosystems, with PS I showing a larger total light-harvesting capacity than PS II. Furthermore, as judged from the measurements of low temperature fluorescence spectra, the light energy absorbed by Chl b was efficiently transferred to PS I in both algae. Based on the above results, it is hypothesized that marine green algae require a higher ATP:NADPH ratio than do terrestrial plants to grow and survive under a coastal environment. [ABSTRACT FROM PUBLISHER]

Cell surfaces of biflagellate gametes and their morphological changes during fertilization ofBryopsis maximaOkamura were observed using a high-resolution field emission scanning electron microscope. Male gametes have broad and narrow faces, which are divided into at least five morphologically distinct regions: 1) the apical plate is a plate-like structure that is approximately 380–530 nm long and approximately 190 nm wide, in the center of the papilla and slightly protruded from the plasma membrane; 2) strips are smooth materials on ridges that originate from the basal part of the papilla and extend downward; 3) the lateral belt is a belt-shaped structure on the center of the narrower faces; 4) the flagellar surface; and 5) the other region of the cell body has a fine-grained appearance. In contrast, the entire female gamete surface is rough because of many granular or amorphous cell coats on the plasma membrane. When both gametes were mixed together, the initial fusion proceeded between the broader face of the male gamete and the anterior side of the female one near the basal bodies. Morphology of the male gamete's cell surface changed gradually as fusion proceeded and was covered by the granular materials; that surface closely resembled those of female gametes except for the apical plate. It was present until the planozygote attached itself to the substrate by the papilla. It finally disappeared after settlement. Therefore, these results indicate that gametes ofB. maximahave sex-specific surface structures that change their morphology during fertilization and settlement. [ABSTRACT FROM AUTHOR]

Summary The purpose of this study was to construct a cosmid library from chromosomal DNA of a marine macroalga, Bryopsis maxima Okamura ex Segawa (Bryopsidales, Ulvophyceae), in a rapid, simple and inexpensive manner. In the DNA purification, polysaccharides were removed by covalently binding them to resin particles containing free boric acid groups. The DNA yield was 20 µg g-1 of B. maxima fresh weight. This DNA was 100-200 kb in length, and its A260 /A280 and A230 /A260 ratios were 1.8 and 0.4, respectively. It was of sufficient quality for molecular research. The cloning procedures were carried out in the following steps: controlled partial shearing of purified DNA through a micro­syringe, optimal size separation of the DNA by biased sinusoidal field gel electrophoresis, ligation of the DNA to the cosmid vector in the gel, and in vitro packaging into the lambda phage. The library consisted of 2.0 × 103 independent clones with an average insert size of 40 kb. The fragment amplified by polymerase chain reaction in the library was hybridized with a DNA fragment (328 bp) encoding B. maxima glutamate dehydrogenase under high-stringency conditions by Southern blot analysis, thus demonstrating that the library contained B. maxima chromosomal DNA. This cosmid library is the first to be constructed for any species of marine macroalgae. [ABSTRACT FROM AUTHOR]

NADP-glutamate dehydrogenase (EC 1.4.1.4; NADP-GDH) was purified to electrophoretic homogeneity from the multinuclear-unicellular green marine alga in Sipho-nales, Bryopsis maxima, and its properties were examined. Mr of the undenatured enzyme was 280 kDa, and the enzyme is thought to be a hexamer of 46 kDa subunit protein. Optimum pHs for the reductive amination and oxidative deamination were 7.5 and 8.2-9.0 respectively. The enzyme displayed NADPH/NADH-specific activities with a ratio of 18 :1. Apparent Km values for 2-oxoglutarate, ammonia, NADPH, glutamate and NADP+ were 3.0, 2.2, 0.03, 3.2 and 0.01 mM respectively. The enzymochemical characteristics of the GDH were studied and compared to those of other species. The B. maxima GDH was insensitive to 5 mM Ca2+ and to 1 mM EDTA in contrast to higher plant NAD-GDHs. Chemical modifications with DTNB and pCMBS suggested that cysteine residues are essential for the enzymatic activity as in other species GDHs. The GDH was not affected by 1 mM purine nucleotides, suggesting that the enzyme is not allosteric, in contrast to animal NAD(P)-GDHs and fungal NAD-GDHs. [ABSTRACT FROM AUTHOR]

The article presents information about Glutamine Synthetase and Glutamate Synthase System of the Marine Green Alga. It has recently been claimed that glutamine synthetase (GS) and glutamate synthase mainly catalyze the first step of reductive amination of amino acids in green plants. Historically, the GS from Escherichia coli was first extensively purified, and its enzymatic properties were studied in detail. In this study, authors attempted to use the techniques of thin layer chromatography and amino acid autoanalysis without using isotopic technique for the determination of reaction products, and appreciable results were obtained.

The fate of chloroplast nuclei (cp-nuclei) and mitochondrial nuclei (mt-nuclei) was followed during gametogenesis in male and female coenocytic thalli in the anisogamous alga Bryopsis maxima by epifluorescence microscopy, after staining with 4′,6-diamidino-2-phenylindole (DAPI), by quantification of chloroplast DNA (cp-DNA) by fluorimetry using a video-intensified, photon-counting system (VIMPICS), and by CsCl density gradient centrifugation. The male and female coenocytic thalli, 48 h before the release of gametes, contain a large number of chloroplasts, each of which is larger in size than the cell nucleus and the mitochondria and contains about 150 cp-nuclei. The size of each chloroplast in the female and male gametangia decreases markedly during gametogenesis as a result of continuous divisions till about 10 h before the release of gametes and, eventually, the numbers of cp-nuclei per chloroplast in the male and female gametangia fall to about 20 and 5, respectively. Two hours later, as the preferential digestion of cp-DNA in the male gametangium occurs, the number of cp-nuclei in the chloroplast of each male gamete falls to zero while the number of cp-nuclei in female gamete does not change, even after release of female gametes. Several mt-nuclei are observed in all of the female gametes. By contrast, the mt-nuclei in the bulk of the male gametes disappear but those in a few gametes remain. The profiles after CsCl density gradient centrifugation of DNAs extracted from male and female plants and gametes support the cytological data. The results suggest that the preferential digestion of cp-DNA in male plants occurs about 8 h before the release of gametes and that there is differential digestion of cp-DNA and mitochondrial DNA (mt-DNA). [ABSTRACT FROM AUTHOR]