Comparative studies on pigments and photosynthetic characteristics of sexually different vegetative and reproductive tissues of Porphyra katadai var. hemiphylla (Bangiales, Rhodophyta)

Porphyra katadai Miura var. hemiphylla Tseng & T.J. Chang, a native species of China, is monoecious with female and male parts in distinct halves separated by a longitudinal line in the blades, and photosynthetic characteristics and pigment contents were compared among different tissues. Female parts contained significantly more phycobiliprotein and carotenoids than male parts did, accompanied by higher photochemical efficiency of photosystem II than the latter. Vegetative tissues had more pigments and higher ΔF/F _m′ and F _v/F _m than their respective reproductive tissues, and male reproductive tissues even exhibited lower P _max based on oxygen evolution than their vegetative tissues at 5–10 °C. Female vegetative tissues showed the highest ΔF/F _m′ among all tissues, while male reproductive tissues had the lowest P _max at low temperatures and the lowest pigment contents. Photosynthesis rates reached the highest values at 10 °C and the lowest values at 20 °C in most tissues, but male reproductive tissues exhibited the best performances at 20 °C, which rarely happened in its natural habitats and growth season. Thus growth capacity and response to seasonal temperature change varied not only between vegetative and reproductive tissues but also between female and male tissues in P. katadai var. hemiphylla, accompanied by their different color and size on wild plants.     

Protoplast isolation and fusion in Porphyra (Bangiales,Rhodophyta)

Two sediment sampling campaigns were conducted in 1978 and 1988 in Lake Geneva (Switzerland). Organic carbon, total nitrogen, total phosphorus and its various forms were analyzed. Results indicate a stability of organic carbon and nitrogen mass, and a significant increase of phosphorus. The variation of phosphorus mass is related to the increase of nonapatite inorganic phosphorus. This study attempts to quantify the phosphorus exchanges at the water sediment interface. The dissolved oxygen level in the bottom water determines the exchange direction. In aerobic conditions, sediments accumulate the excess of phosphorus, while in anaerobic conditions, they constitute an internal source.     

Nuclear division of the vegetative cells, conchosporangial cells and conchospores of Porphyra yezoensis (Bangiales, Rhodophyta)

To confirm the position and timing of meiosis in Porphyra yezoensis Ueda, the nuclear division of vegetative cells, conchosporangial cells and conchospores was observed. An improved staining method using modified carbol fuchsin was introduced to stain the chromosomes of Porphyra. Pit‐connections between conchosporangial cells also stained well with this method. Leptotene, zygotene, pachytene, diplotene, diakinesis, metaphase, anaphase and telophase were observed in the conchosporangial cells. During the germination of conchospores, no characteristics of meiosis I were found. No difference between the nuclear division of vegetative cells and that of conchospores was observed, and 2–3 days were needed for the first cell division both in vegetative cells and conchospores. Therefore, the cell division that occurs during conchospore germination is not meiosis I. Our results indicate that the prophase of meiosis I begins during the formation of conchosporangial branches, and metaphase I, anaphase I and telophase I take place during the maturation of conchosporangial branches. Then the three‐bivalent nucleate sporangia complete cell division to form two individual conchospores, each with one three‐univalent nucleus. The conchospores released from the sporangia are at meiotic interphase. Meiosis II occurs at the first nuclear division during conchospore germination, which is a possible explanation for the observation of mosaic thalli in mutant germlings of P. yezoensis. The mosaic thalli might also arise from gene conversion/post meiotic segregation events, comparable to those in Sordaria fimicola (Roberge ex Desm.) Ces. & De Not. and Neurospora crassa Shear & B.O. Dodge.     

The ionic relations of Porphyra purpurea(Roth) C.Ag. (Rhodophyta, Bangiales)

Abstract Radioisotope equilibration techniques have been used to determine the intracellular concentration of K⁺, Na⁺ and Cl_?, together with the unidirectional ion fluxes across the plasmalemma of Porphyra purpurea. Influx and efflux of ⁴²K⁺, ²⁴Na⁺ and ³⁶C1^? are biphasic, the rapid, initial uptake and loss of tracer from individual thalli being attributable to desorption from extracellular regions. Cellular fluxes are slower and monophasic, cells discriminating in favour of K⁺ and Cl^? and against Na⁺. A comparison between the equilibrium potential of individual ion species and the measured membrane potential demonstrates that there is an active component of K⁺ and Cl^? influx and Na⁺ efflux. ‘Active’ uptake and ‘passive’ loss of K⁺ and Cl^? are reduced when plants are kept in darkness, suggesting that a fraction of the transport of K⁺ and Cl^? may be due to ‘exchange diffusion’ (K⁺/K⁺ and Cl^?/Cl^?antiport).     

Estimation of the degree of self-fertilization in Porphyra yezoensis (Bangiales,Rhodophyta)

Crosses between genotypically distinct thalli of the monoecious species Porphyra yezoensis were carried out using immature thallus fragments from green- and red-type color mutants and also wild-type thalli. As the genes governing the mutants are monogenic, recessive to the wild-type, and belong to the same linkage group, the degree of self-fertilization could be estimated based on the pigmentation of the resultant diploid conchocelis. The degree of self-fertilization in the cross between the green-type and the wild-type was 48.5–55.0%, and in the cross between the red-type and the wild-type was 45.1–56.5%. In the cross between the green- and red-type mutants, the degree of self-fertilization was 46.0–54.5% when the green-type was the female parent, and was 44.8–55.6% when the red-type was the female parent.     

Induction and characterization of pigmentation mutants in Porphyra yezoensis (Bangiales, Rhodophyta)

Porphyra yezoensis Ueda conchospore germlings (1–4-cell stages) were treated with N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) for inducing mutations. Three kinds of color-mutated gametophytic blades, which were composed of the mutated cells wholly, sectorially or spottedly, were obtained; and most of them were sectorially variegated blades. The highest frequency of these mutated blades was 1.3%. Four different pigmentation mutant strains were obtained by regenerating single cells and protoplasts that were enzymatically isolated from the mutated sectors of the sectorially variegated blades. The mutants were relatively stable in color in both gametophytic blade and conchocelis phases. In the two phases, each mutant strain showed characteristic differences in the in vivo absorption spectra, and had different pigment contents of major photosynthetic pigments (chlorophyll a, phycoerythrin and phycocyanin) as compared with the wild-type and with each other. The gametophytic blades from the four mutant lines showed significant differences in growth and photosynthetic rates, when they were cultured in the same conditions. By crossing the mutant with the wild-type, it was found that the color phenotypes of two mutants reported above, were resulted from two mutations in different genes, respectively. This revised version was published online in August 2006 with corrections to the Cover Date.     

Life history in culture of the obligate epiphyte Porphyra subtumens (Bangiales, Rhodophyta) endemic to New Zealand

This is the first report of the growth in culture of Porphyra subtumens J. Agardh ex Laing (Bangiales, Rhodophyta), an obligate epiphyte of Durvillaea species and endemic to New Zealand waters. Archeospores, previously observed on field material, develop directly into the blade phase. Spores released from field collected blades form conchocelis. Conchospores develop into new blades, completing the life history in culture. Earlier reports of reproduction in P. subtumens gave conflicting accounts with some authors citing this species as having an asexual, monophasic life history with an unusual form of spore production, while others described spermatangia and carposporangia on the blade phase.     

Rapid extraction of high-quality genomic DNA from Porphyra yezoensis (Bangiales, Rhodophyta)

We developed a simple, rapid and stable method for extraction of high molecular weight DNA from the marine red alga Porphyra yezoensis Ueda using both guanidium treatment and QIAGEN? kit (Funakoshi, Tokyo, Japan). The method does not require expensive equipment and complex steps. The DNA yield averaged 1.5 μg 100 mg^?1 of Porphyra tissue and the A260/A280 and A230/A260 ratios of the DNA were approximately 1.8 and 0.4, respectively. It was of sufficient quality to be used for not only polymerase chain reactions but also other DNA manipulation techniques such as restriction digestion and construction of genomic libraries.     

Genetic analysis of artificial pigmentation mutants in Porphyra yezoensis Ueda (Bangiales, Rhodophyta)

Porphyra yezoensis Ueda artificial pigmentation mutants, yel (green), fre (red‐orange) and bop (pink), obtained by treatment with /V‐methyl‐/V′‐nitro‐N‐nitrosoguanidine, were genetically analysed. The mutations associated with color phenotypes are recessive because all of the heterozygous conchocelis resembled the wild type color when they were crossed with the wild type (wt). In the reciprocal crosses of yel × wt, both parental colors and eight types of blades appeared in the F₁ gametophytic blades from the heterozygous conchocelis. Both colors segregated in the sectored F₁ blades in a 1:1 ratio, indicating that the color pheno‐type of yel resulted from a single mutation in the nuclear gene. In the reciprocal crosses of fre × wt, however, four colors and more than 40 types of blades appeared in the F₁ blades from the heterozygous conchocelis, indicating that the color phenotype of fre resulted from two mutations in different genes. In the reciprocal crosses of bop×wt, three colors and 12 types of blades were observed in the F₁ blades from the heterozygous conchocelis. Both parental colors appeared far more frequently than the third new color. These results indicated that the color phenotype of bop resulted from two closely linked mutations in different genes, and the epistasis occurred in the F₁ blades. The mutants, yel, fre and bop, differ from the spontaneous green (C‐O), the red (H‐25) and the violet (V‐O) mutants of P. yezoensis, respectively.     

Cyclophilin Participates in Responding to Stress Situations in Porphyra haitanensis (Bangiales,Rhodophyta)

Porphyra haitanensis (T. J. Chang & B. F. Zheng) is an important economic alga found off the southern coast of China. It has evolved a strong tolerance against stress, which is an important survival characteristic. Cyclophilin has been shown to be involved in the stress response of plants and algae. To investigate the tolerance against stress in Porphyra, we isolated the cyclophilin PhCYP18 gene (Accession number JQ413239 ) and measured its expression over different generations and stress conditions. In P. haitanensis, cyclophilin PhCYP18 accumulated more in the filamentous sporophyte generation than in the blade gametophyte generation. This difference was thought to be due to harsh environments and a gene dosage effect. It has been found, however, that PhCYP18 expression was dysregulated in blades under high salt stress, strong irradiance stress and multifactorial stress compared to blades under normal conditions. Moreover, the changes were not linearly related to the degree of stress. It was therefore thought that PhCYP18 actively responded to stress situations and induced strong stress tolerance, which is evident in P. haitanensis.     

The Supramolecular Organization of Photosynthetic Membranes of the Thallus Stage of Porphyra leucosticta Thuret. (Bangiales,Rhodophyta) Visualized by Freeze-Fracture

The supramolecular organization of the thylakoid membranes of the thallus stage in the red alga Porphyra leucosticta is studied in replicas of rapidly frozen and fractured cells. Freeze-fractured thylakoid membranes exhibit only two types of fracture faces (EF and PF), because the lamellae in red algal chloroplasts are not stacked. The PF reveals numerous, tightly packed, but randomly distributed particles (density range from 2970 to 3550 particles/μm²). In contrast, the EF particles appear organized into parallel rows, the spacing of which is about 60–70 nm (about 8–9 particles occur along 100 nm of the line that is formed). Significant numbers of single EF particles are randomly distributed between the EF particle rows. The particles on both fracture faces (PF and EF) fall into two size classes: 10 to 11 nm (major size class) and 14 to 15 nm (minor size class).     

Tolerance to oxidative stress induced by desiccation in Porphyra columbina (Bangiales, Rhodophyta)

Unravelling the mechanisms underlying desiccation tolerance is crucial in order to understand the position of algal species in the intertidal zone. The alga Porphyra columbina lives in the uppermost part of the rocky intertidal zones around the world and was selected as a model for this study. Naturally desiccated plants were collected during low tide and studied for morphological changes, oxidative burst induction, biomolecule oxidation, antioxidant responses, and photosynthetic status. Naturally hydrated plants collected during high tides were used for comparative purposes. In addition, changes induced by desiccation were assessed in vitro and the capacity to recover from desiccation was determined by rehydrating the fronds in seawater. The global results show that desiccation induces morphological and cellular alterations accompanied by a loss of ～96% of the water content. Overproduction of reactive oxygen species (ROS) was induced by desiccation and two peaks of H(2)O(2) were detected at 1 and 3 h of desiccation. However, during in vitro rehydration post-desiccation, the ROS quickly returned to the basal levels. At the biomolecular level, only a low production of oxidized proteins was recorded during desiccation, whereas the activity of diverse antioxidant enzymes increased. However, this activity diminished to near basal levels during rehydration. The photosynthetic efficiency (F(v)/F(m)) during desiccation declined by 94-96% of the values recorded in hydrated plants. This reduction was generated by the low levels of trapped energy flux per cross-section (TRo/CS), electron transport flux per CS (ETo/CS), and density of reaction centres (RC/SCo) as well as the chlorophyll content. The inverse pattern was observed for the levels of phycocyanin and phycoerythrin content. F(v)/F(m) and the photosynthetic indicators were restored to normal levels after only 5 min of rehydration. The results indicate that desiccation in P. columbina causes overproduction of ROS that is efficiently attenuated. The morphological and photosynthetic changes could be operating as tolerance mechanisms due to the fact that these responses principally prevent biomolecular alteration and cellular collapse. Thus, the activation of different physiological mechanisms helps to explain the high tolerance to desiccation of P. columbina and, at least in part, the position of this species at the highest level in the intertidal zone.     

Porphyra drewiana, a new species of red algae (Bangiales, Rhodophyta) from Brazil

Porphyra drewiana Coll et Oliveira, sp. nov., is described from plants collected on the south‐east coast of Brazil. The species proposed is monostromatic, monoecious, monoplastidial, without marginal microscopic teeth and does not produce monospores. Both phases, leafy and filamentous, have three chromosomes. Morphologically the most similar species is Porphyra spiralis Oliveira et Coll var. amplifolia Oliveira et Coll, from which it differs by: (i) thallus gross morphology; (ii) scattered pluristromatic areas of vegetative cells; (iii) division of the plastids prior to the nucleus at the first division of the carpospores mother cell; (iv) the number of carpospores and spermatia produced per mother cell; and (v) morphology and behavior of the filamentous phase in cultures. An identification key for the species referred to Brazil is included.     

Morphological and AFLP variation of Porphyra yezoensis Ueda form, narawaensis Miura (Bangiales, Rhodophyta)

Detailed morphological observations were made on two strains of cultivated Porphyra: HG‐1 (pure line isolated from Dai‐1) and Noriken‐4 (parental strain of a pure line HG‐4). The two strains were identified as P. yezoensis f. narawaensis based on their macroscopic and microscopic features, such as long linear or oblanceolate blades up to 50 cm in maximum length, division formulae of spermatangia and zygotosporangia, shape of trichogynes and carpogonia, and the second transverse divisional plane formed at the division from c/2 to c/4 in zygotosporangia. Gametophytic blades from two completely homozygous conchocelis strains isolated in this study (HG‐1 and HG‐4) were cultured under the same conditions and compared to confirm whether the differences in their shapes are genetically determined. The shape of blades from both of conchospores and monospores was always more slender in HG‐4 than in HG‐1 at the same blade age, suggesting that the difference in the blade shape between the two pure lines is due to genetic variation. To estimate the level of genetic variation the two pure lines were subjected to amplified fragment length polymorphism fingerprint analysis. A total of 230 bands were detected in HG‐1 and HG‐4 using eight selective primer pairs, and the number of polymorphic bands was only two in HG‐1. These results indicate that the two pure lines certainly show genetic variation, which is, however, at an extremely low level. The importance of pure‐line breeding and the origin of currently cultivated Porphyra are discussed. This is the first report to identify currently cultivated Porphyra strains in Japan based on combined results of detailed morphological observations and molecular analysis.     

Research Note: Simple molecular discrimination of cultivated Porphyra species (Porphyra yezoensis and Porphyra tenera) and related wild species (Bangiales,Rhodophyta)

To discriminate between cultivated Porphyra species (Porphyra yezoensis and Porphyra tenera) and closely related wild Porphyra species, we developed a polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) analysis of the rbcL gene using five restriction enzymes. Although our previous PCR‐RFLP analyses of internal transcribed spacer (ITS) rDNA and plastid RuBisCO spacer regions could not always discriminate wild P. yezoensis, wild P. tenera, and closely related wild species, the PCR‐RFLP profiles of the rbcL gene were useful in discriminating samples collected from natural habitats. Therefore, PCR‐RFLP analysis of the rbcL gene will help in the simple identification of a large number of samples, not only for the establishment of reliable cultures as breeding material, but also for the taxonomic investigations of species that are closely related to cultivated Porphyra.     

Conchospore production and seasonal occurrence of some Porphyra species (Bangiales,Rhodophyta) in Washington State

The leafy thalli of species of the marine red algal genus Porphyra grow rapidly but persist for a relatively short time on rocky intertidal or subtidal substrata or as epiphytes on other marine plants. In most species, the large, short-lived leafy thalli alternate with small, presumably perennial, filamentous conchocelis plants. Depending on the species of northeastern Pacific Porphyra, photoperiod and temperature are important regulators of conchospore formation and release. Data from laboratory studies of conchospore formation and release in five Washington species of Porphyra (P. abottae, P. nereocystis, P. perforata, P. pseudolanceolata and P. torta) indicate that conchospores are most likely to be released at a time that precedes the appearance of the leafy thalli in the field.     

Inorganic carbon acquisition by two Antarctic macroalgae,Porphyra endiviifolium (Rhodophyta: Bangiales) and Palmaria decipiens (Rhodophyta: Palmariales)

Aspects of the physiology of two rhodophyte macroalgae from the Antarctic, Palmaria decipiens and Porphyra endiviifolium, were examined. Both species showed low light compensation points and I _k values. Measurements of the dissolved inorganic carbon dependent kinetics of oxygen evolution gave values for K _0.5 (CO₂) of 10.5 and 3.7 μM for Palmaria and Porphyra respectively. These values are lower than expected from the kinetic properties of ribulose 1,5-bisphosphate carboxylase oxygenase and imply that the two species are capable of the active transport and accumulation of dissolved inorganic carbon by a “CO₂ concentrating mechanism”. Both organisms are able to use bicarbonate from the bulk medium. These features are similar to those found in temperate species and thus, despite the low photon flux, low temperatures and consequent elevated CO₂ concentrations in seawater at air-equilibration, the Antarctic rhodophytes examined appeared not to have a diminished capacity for transport of dissolved inorganic carbon and internal CO₂ concentration. Accepted: 24 October 1998