Search

Bangia fuscopurpurea is a farmed species in the ancient family Bangiales. It inhabits upper intertidal zones and suffers periodical desiccation and osmotic stress. The transcriptomic regulation under dehydration and hyposalinity was investigated. The differentially expressed genes (DEGs) accounted for 18.7% of the unigenes obtained by de novo transcriptome assembly (|log2fold-change| ≥ 1, FDR ≤ 0.001). Over 72% of the DEGs were downregulated under stress. The DEGs were predominantly enriched into the KEGG pathways “metabolic pathways,” “ribosome,” “biosynthesis of secondary metabolites,” “protein processing in endoplasmic reticulum,” and “oxidative phosphorylation.” The optimum photosynthetic efficiency (Fv/Fm) and photochemical quenching (qP) dropped significantly with 89% relative water loss and recovered rapidly after being rehydrated. Most DEGs regarding “photosynthesis” and “C3 carbon fixation” were upregulated in the dehydrated thalli, which may enable the thalli to gain photosynthetic recovery once being rehydrated. Fv/Fm and qP decreased significantly with 1 h of 90% freshwater treatment and then recovered to the control level 1 day later. With 6 h hyposaline treatment, expression of plasma membrane H+-ATPase genes was strongly and predominantly induced while the mRNA abundance of vacuolar, chloroplastic, and mitochondrial H+-ATPase genes decreased or showed no significant change. Some transporter, ion channel, and transmembrane protein genes together with the gene-encoding key enzymes involving in proline and heteroside metabolism were upregulated under hyposalinity. The results indicated that transmembrane exchange of ion and osmolytes was induced under hyposalinity to balance the osmotic fluctuation, which seemed to be triggered by plasma membrane H+-ATPases. These findings will facilitate elucidating the stress acclimation mechanism of B. fuscopurpurea.

Conchocelis cultivation is a crucial step in the industrial growth of Pyropia (laver). However, our knowledge of the seawater microbiology community in Pyropia seedling pools is limited. This study investigated the temporal dynamics in seedling pool microbiota before and after outbreaks of yellow spot disease in Pyropia yezoensis conchocelis. A total of 18 water samples were collected to assess seedling pool health status, followed by the sequencing of microbiota 16S ribosomal RNA (rRNA). Analysis of 16,760,224 16S rRNA gene sequences indicated that the core microbe group comprised 207 genera. The microbial diversity of samples gradually increased from May to July. The bacterial diversity of seawater samples from diseased P. yezoensis seedling pools was significantly higher than samples from healthy seedling pools. It is noteworthy that each pool group had a distinctive microbial community composition. The relative abundance of two dominant bacteria genera, Sediminicola and Roseivirga, increased over time in healthy seedling pools, peaking in August, while Vibrio remained at constantly low levels. However, the abundance of Vibrio and Polaribacter increased sharply in diseased P. yezoensis seedling pools and decreased after fresh seawater exchange. This indicates that these bacteria are probably associated with the filament disease. Many disease-associated bacteria are negatively related to the HCO3 − concentration in seawater and positively related to pH. Changes in bacteria and environmental factors reflect the characteristics of microbial community succession in seedling pools and therefore have potential to be used as biomarkers and environmental signals for Pyropia disease monitoring.

The ribosomal intergenic spacer (IGS) variation was compared for the nine main cultivated varieties of Pyropia yezoensis in China obtained from the Chinese National Pyropia Germplasm Repository. The full length of the IGS is 5984 bp including several sequence repeats and some complex structures. The sequence analysis of four partial IGS amplicons ranged from 3628 bp to 3776 bp; and the G+C content is 52.5%. Through similarity analysis and multiple sequence alignment of these partial IGS amplicons from the nine varieties, we have found 278 variable sites which account for approximately 7.5% of the whole IGS length. Both comparison of partial IGS sequences and phylogenetic analysis indicate high levels of genetic variation among different P. yezoensis cultivars in different areas of China. In comparison to the IGS of P. haitanensis, this study highlights the important function of classification of IGS in P. yezoensis. Therefore, the IGS sequence may be used to identify intraspecific variation in P. yezoensis.

The complete nuclear ribosomal DNA (nrDNA) cistron sequence of Pyropia yezoensis has been sequenced, of which each unit is composed of the intergenic spacer (IGS), the small-subunit (SSU) ribosomal RNA (rRNA) gene, the internal transcribed spacer 1 (ITS1), the 5.8S rRNA gene, the internal transcribed spacer 2 (ITS2), and the large-subunit (LSU) rRNA gene. This cistron occurs in tandem repeats that can number in 100s to 1000s. Furthermore, in the analysis of the sequence data, we determined that introns were present in the small-subunit rRNA genes, for which the exon sequences (1834 bp) are almost identical. The intron numbers ranging from zero to two in the small-subunit rRNA genes are different between multiple individuals. However, the full length of the large-subunit rRNA genes is 4770 bp without any introns, and the 5.8S rRNA gene is 159 bp. Moreover, the 5′ and 3′ terminal sequences of the genic regions of the ribosomal cistron are extremely conservative even among various species in red alga. In addition, the range for ITS1 is 371–372 bp and for ITS2 is 532 to 535 bp. The IGS is 5984 bp in length and possesses upstream direct repeats, downstream repeats, and middle inverted repeats that make sequencing untoward. This is the first time that the complete nucleotide of the IGS region of P. yezoensis has been sequenced. The provision of the full length of nrDNA cistron will offer useful information to be widely utilized for identification, taxonomic relationships, and phylogenies in red algae.

The photosynthetic characteristics of a Pyropia haitanensis red mutant mutated from a wild-type strain using chemical mutagens were studied. The aim was to compare the differences in photosynthetic characteristics between the red mutant and the wild type, and then to analyse the possibility of the red mutant as breeding material. The results indicated that the cytoplasm thickness of the red mutant and the wild type were similar, whereas the cell wall of the red mutant was significantly thinner than that of the wild type. Additionally, the chlorophyll a extract absorption spectra of both strains exhibited no obvious difference, whereas the absorption peaks at 498, 545, and 565 nm (which belong to phycoerythrin, PE) in the phycobiliprotein extract absorption spectra of the red mutant were clearly higher than those of the wild type. The PE content per area of the red mutant thallus was significantly higher than that of the wild type, and the ratios of PE to phycocyanin (PC) and PE to chlorophyll a were significantly higher in the red mutant than in the wild type. The net photosynthetic oxygen evolution rates of the red mutant and wild type cultured under different light intensities demonstrated that the oxygen evolution rates of all samples decreased with increasing light intensities, whereas the oxygen evolution rate of the red mutant was higher than that of the wild type under the same light intensities. The light response curves also indicated that the light-saturated photosynthetic rates (P max), light saturation points (LSPs), and light compensation points (LCPs) of both strains decreased to different degrees with increasing light intensities and that the P max and LSP values of the red mutant were significantly higher than those of the wild type under identical light intensities. In contrast, there were no obvious differences in the respiration rate (R d) and in the LCP. The F v/F m values of both strains were similar before light treatment, whereas the F v/F m of the red mutants after culture under different light intensities (120 and 200 μmol photons m−2 s−1) for 3 days were significantly higher than those values of the wild type. Moreover, ∆F/F m′ also exhibited a similar variation. Based on these results, the high content of PE in the P. haitanensis red mutant causes a steady red phenotype, and the increase in the PE concentration and the decrease in the thickness of the thallus may enhance its photosynthetic physiological activity. Thus, the red mutant of P. haitanensis may provide good material for Pyropia breeding.

Carotenoid metabolism in red algae is not well understood. Geranylgeranyl diphosphate (GGPP), synthesized by GGPP synthase (GGPS), is a precursor for the biosynthesis of many biologically important metabolites, including carotenoids and chlorophylls. GGPSs have been functionally characterized in many organisms, but not in species of the primitive red algal order Bangiales. Here, we cloned and characterized the gene encoding GGPS (PuGGPS) in Pyropia umbilicalis (Bangiales). PuGGPS encodes a protein of 345 amino acids with an N-terminal transit peptide. The catalytic activity of PuGGPS for the production of GGPP was verified by a color complementation assay in Escherichia coli and subsequent high-performance liquid chromatography analysis. Homology modeling of PuGGPS showed that its tertiary structure resembles that of other known GGPSs and that this structure allows for the precise docking of the enzymatic product of PuGGPS, GGPP. When leafy thalli of P. umbilicalis were treated with norflurazon, an inhibitor of the key carotenoid metabolism enzyme phytoene desaturase, the expression of PuGGPS increased by twofold compared with that of the control in the first 2 h, suggesting a prompt response to metabolic perturbation. Prolonged norflurazon treatment failed to increase PuGGPS expression. Sequence analysis showed that PuGGPS shares seven conserved motifs with other previously identified GGPSs from different organisms, including two aspartate-rich GGPS signature motifs. Phylogenetic analysis also indicated that PuGGPS is a member of the type II GGPSs found in eubacteria and plants.

The metabolic pathway of 8-heptadecene in red algae was investigated. The results showed that the amounts of 8-heptadecene in the primitive bangiophycidean red algae Pyropia and Bangia were 30–50 % of the volatile compounds, much higher than that in the green alga Ulva pertusa, the brown alga Sargassum thunbergii and the florideophycidean red alga Gracilaria lemaneiformis. Studies on the metabolism of 8-heptadecene in Pyropia found that its enzymatic system has no significant catalytic activity on palmitic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid. However, the isolated enzymatic solution showed activity in the presence of eicosapentaenoic acid. This activity produced about four times the amount of 8-heptadecene compared with other substrates and the control, indicating the solution had a specific catalytic function for eicosapentaenoic acid. Furthermore, the enzyme solution was strongly inhibited by NaN3 but not by phenidone and phenanthroline suggesting that the enzyme is structurally related to heme protein. Thus, it is believed that a constant amount of 8-heptadecene is maintained in the primitive red alga Pyropia and the 8-heptadecene is a metabolite of eicosapentaenoic acid and may catalyzed by enzymes including a heme lipoxygenase-like enzyme.

The photosynthetic characteristics of thalli of cultured Pyropia yezoensis strains collected in January, February, and March in seaweed cultivation area of South China Yellow Sea were studied. Results showed that the maximum quantum efficiency (F v/F m) of all P. yezoensis thallus collected at different times was 0.65. The actual quantum efficiency (ΔF/F m′) of samples in January was the lowest of all samples, while the ΔF/F m′ of samples in March was significantly higher than those in January and February. The increase of temperature and photosynthetic pigments ratios of phycoerythrin and chlorophyll a (PE/Chla) and phycocyanin and chlorophyll a (PC/Chla) from January to March may be the important reasons for the increase in light use efficiency of thallus; although the thallus in March was significantly thicker than in January which may have reduced the light energy absorbed by photosynthetic pigments, the increase of relative high energy use efficiency also helped to maintain the photosynthetic oxygen evolution rate in March. The thicker thallus also reduced photodamage, and the thallus area was increased obviously in March, so the growth rate of thallus in March was over 35 % higher than that in February. Our research indicates that the photosynthetic characteristics of P. yezoensis strains thalli have a close relationship with their growth stage and environmental factors especially temperature, and those photosynthetic characteristics are also reflected in the growth rate of the thalli.

In this study, chlorophyll fluorescence parameters (∆F/F m′, F v/F m) and oxygen evolution of female vegetative tissues of Porphyra katadai var. hemiphylla in unisexual culture (FV) and in mixed culture with male vegetative tissues (FV-M) were followed at 5–20 °C, 10 and 80 μmol photons m−2 s−1. The formation of reproductive tissues was closely correlated with decreasing photosynthetic activities. At the same temperature the tissues cultured under 80 μmol photons m−2 s−1 showed a greater extent of maturation than those under 10 μmol photons m−2 s−1, and their decrease in photosynthesis was also larger. Under the same light intensity the extent of maturation increased with increasing temperature, and both cultures showed higher values of ∆F/F m′ and F v/F m at 10 and 15 °C, while their oxygen evolution became negative at 15–20 °C during the later period. Under the same culture condition the maturation of FV-M culture was relatively faster than that of FV culture, while their photosynthetic activity, especially ∆F/F m′, was lower.

Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi (previously called Porphyra yezoensis) is an economically important alga. The blades generated from conchospores are genetic chimeras, which are not suitable for genetic similarity analysis. In this study, two types of blades from a single filament of P. yezoensis sporophyte filament were obtained. One type, ConB, consisted of 40 blades that had germinated from conchospores. The other type, ArcB, consisted of 88 blades that had germinated from archeospores released from ConB. Both of them were analyzed by amplified fragment length polymorphism. The low genetic similarity levels for both conchospore-germinated and archeospore-germinated blades demonstrated that the conchcelis we used was cross-fertilized. Furthermore, a higher polymorphic loci ratio (98.6%) was detected in ArcB than in ConB (80.7%), and the average genetic similarity of ArcB (average 0.61) was lower than that of ConB (average 0.71). These differences indicated that genetic analysis using ArcB gives more accurate results.

Photosynthetic characteristics of four Porphyra yezoensis Ueda [a taxonomic synonym of Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi] strains in conchocelis phase were investigated and compared with one wildtype of P. yezoensis and two strains of Porphyra haitanensis T. J. Chang et B. F. Zheng [a taxonomic synonym of Pyropia haitanensis (T. J. Chang et B. F. Zheng) N. Kikuchi et M. Miyata]. Results showed that experimental strains had higher contents of chl a and carotenoids, but a lower content of total phycobiliproteins than the wildtype. Meanwhile, photochemical efficiency of PSII was measured using pulse amplitude modulation (PAM) fluorometry technology. The value of PSII photosynthetic parameters of P. yezoensis strains were all higher than the wild strain, and the maximal quantum yields (Fv /Fm ), effective quantum yields Y(II), and relative photosynthetic electron transport rates (rETR) of P. haitanensis were higher than those of P. yezoensis. The present study verified the possibility of selective breeding of P. yezoensis using the filamentous sporophyte instead of the gametophytic thallus, the advantages being (i) nonrequirement of control of life cycle and (ii) direct and rapid cultivar improvement by artificial selection. We consider the method to be a promising technique for selective breeding of P. yezoensis cultivars.

The levels of photosynthetic pigments and chlorophyll fluorescence of Porphyra yezoensis strains selected from high-light environments were investigated. Sutong and Sulian strains originated from the same high-light environment but were selected from different sites on the Yellow Sea coast of Jiangsu Province, China. In January (a low temperature period), the Sulian strain and the WT (a widely cultivated strain) had higher levels of chlorophyll a, phycoerythrin, phycocyanin, and allophycocyanin, and higher actual photochemical efficiency of PSII (ΔF/F m′) than the Sutong strain. This indicated that Sulian and the WT may have better adaptation to low temperature. In March (an optimal temperature period), Sutong had higher levels of photosynthetic pigments and higher ΔF/F m′ than the WT and Sulian strains. This suggested that Sutong had higher light use efficiency at optimal temperatures and that most energy absorbed by PSII was used for photosynthetic electron transport. The differing areas of origin of these strains may have resulted in these differences in temperature adaptation.

The formation of archeospores is characteristic of Porphyra yezoensis Ueda and is important for Porphyra aquaculture. Recently, it has been regarded as a valuable seed source for propagation of thalli in mariculture. Cell wall composition changes are associated with archeospore formation in P. yezoensis. Here, we report changes of cell walls of P. yezoensis during archeospore formation. The surfaces of vegetative cells that were originally smooth became rougher and more protuberant as archeosporangia were formed. Ultimately, the cell walls of archeosporangia ruptured, and archeospores were released from the torn cell walls that were left at distal margins of thalli. With changes in cell walls, both effective quantum yield and maximal quantum yield of the same regions in thalli gradually increased during the transformation of vegetative cells to archeospores, suggesting that the photosynthetic properties of the same regions in thalli gradually increased. Meanwhile, photosynthetic parameters for different sectors of thalli were determined, which included the proximal vegetative cells, archeosporangia, and newly released archeospores. The changes in photosynthetic properties of different sectors of thalli were in accordance with that of the same regions in thalli at different stages. In addition, the photosynthetic responses of archeosporangia to light showed higher saturating irradiance levels than those of vegetative cells. All these results suggest that archeosporangial cell walls were not degraded prior to release but were ruptured via bulging of the archeospore within the sporangium, and ultimately, archeospores were discharged. The accumulation of carbohydrates during archeospore formation in P. yezoensis might be required for the release of archeospores.

In January and February 2010, heavy sea ice formed along the coast of the Bohai Sea and the northern Yellow Sea, China. Intertidal organisms were subjected to serious freezing stress. In this study, we investigated the freezing tolerance of the upper intertidal economic seaweed Porphyra yezoensis. The maximum photochemical efficiency of PS II (F v/F m) in undehydrated thalli remained high after 24 h at −2°C and that in dehydrated thalli decreased in a proportion to thallial water loss. F v/F m dropped sharply after 24 h at −20°C, regardless of absolute cellular water content (AWC). The F v/F m in frozen thalli recovered rapidly at 0–20°C. A wide range of water loss in the thalli enhanced their tolerance to freezing. F v/F m values in undehydrated thalli dropped sharply after 3 d at −2°C or 10 d at −20°C while those in dehydrated thalli (20–53% AWCs) remained at high levels after 9 d at −2°C or 30 d at −20°C. These results indicate that P. yezoensis has high freezing tolerance by means of dehydration during the ebb tide and rapid recovery of F v/F m from freezing. A strategy of P. yezoensis industry to avoid heavy loss during freezing season is discussed based on these findings.

Two strains, which are the free-living conchocelis of Porphyra yezoensis Ueda and Porphyra haitanensis T. J. Chang et B. F. Zheng, and four “interspecific hybridization” strains of these two species are investigated. The rbcL genes of 11 samples were amplified and sequenced, each of which were about 1,400 bp with a good specificity. The results of pair-wise distance matrix and multi-alignment showed that pair-wise distance were small while homologous index was large between strains Y-2066, Y-k2001, and Y-H001. These two indexes showed the same level as the above between strains H-2001, Y-hyC1, and Y-hyC2; however, the distances were larger between three former strains and three latter strains. Cluster trees showed the same trend. Fertile strains appeared after 2 years of culture of unfertile interspecific hybridization conchocelis and were separated from that based on different colors. Our finding that these fertile strains can bear offspring is important for understanding the interspecies hybridization of Porphyra. Molecular analysis of the fertile strains based on rbcL gene showed maternal inheritance. We inferred that somatic recombination was one of the reasons making interspecific hybridization strains fertile.

Pigment mutants were used as genetic markers to study the early development and morphogenesis of blades in four species of Porphyra. In Porphyra haitanensis, P. yezoensis, and P. oligospermatangia, the first two divisions are transverse during conchospore germination, yielding four cells arranged in a line. These species are representative of linear development pattern in Porphyra. Resulting in blades with color sectors vertically arranged. In P. katadai var. hemiphylla, the first division is transverse and the upper cell divides vertically forming two side-by-side cells, and its blades are derived mostly from the upper cell showing a bilateral development pattern with two lateral parts of different colors. In this type of germination, most or the entire blade is derived from the upper cells. Some fronds of P. katadai var. hemiphylla developed in linear pattern. In addition, 9.3% of the conchospore germlings of linear development were produced at 10°C, 15.3% at 15°C, and 38.0% at 20°C for conchospore germlings of P. katadai var. hemiphylla. More linear development occurred at higher temperatures. The results revealed general trends of early developmental patterns and morphogenesis of blades within the genus of Porphyra. Developmental patterns and morphogenesis of blades are under the influence of temperatures.

Bangia fuscopurpurea (Rhodophyta) was cultivated in Putian (Fujian province, China). The characteristics of the life history concerned with cultivation were investigated and the cultivation procedure was presented. The gametophytic phase (thallus) and the sporophytic phase (conchocelis) occurred alternately in the life history of B. fuscopurpurea. Young thalli produced archeospores, and the number depended on the environmental factors. Temperature affected the number of archeospore release and percent of germination, and photo flux density (PFD) mainly affected the time of spore release and germination. Thalli matured from December to February and developed into the conchocelis phase through sexual reproduction. The conchocelis grown in shells had three developmental stages: vegetative conchocelis, conchosporangiall formation and conchospore formation. Pit-connections were present in the first 2 stages but absent after conchospore formation. Vegetative conchocelis and conchosporangial. branches can transform into each other. However, conchospores only developed into the gametophytic phase. Cultivation of B. fuscopurpurea was based on characterization of the life history, consisting of 3 steps: zygotospores collection, indoor cultivation of conchocelis and outdoor cultivation of thalli. Young thalli that developed from conchospores produced numerous archeospores before December. Over 90% of the crop was from the development of archeospores. The results indicated that conchosporelings were a good source of archeospores, and the development of the large quantity of archeospores acted as a more prevailing means to increase the population size. (C) 2008 Elsevier B.V. All rights reserved.

The color mutations in Bangiaceae were investigated by treating the blades, conchocelis and conchospores phase of Bangia sp., Porphyra yezoensis, and P. haitanensis sampled in China with mutagen N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). A high percentage of mutation in different expression characteristics in all three phases were shown within optimum mutagen concentrations. Among mutagenized blades, mutations occurred on single cells, which is a direct outcome of mutation of haploid cells. The mutation of mutagenized conchocelis resulted in a two-step process: low-level expression in conchocelis phase, and high-level expression in progeny, explaining that mutation took place in diploid cells. The mutations of conchospores were expressed immediately at germination of spores, indicating a change in ploidy. This paper reports the process of meiosis and its effect on frond development, and the relation between color mutations and morphological characteristics expressed by mutations in Bangiaceae.

Nuclear divisions of carpospores, conchocelis and conchospores of Porphyra yezoensis, P. haitanensis, P. katadai var. hemiphylla and P. oligospermatangia from China were investigated. The observations showed diploid chromosome numbers of 2n = 6 for P. yezoensis and P. oligospermatangia, and 2n = 10 for P. haitanensis and P. katadai var. hemiphylla. For all four species, somatic pairing of chromosome sets was observed in late prophase. Sister chromosomes separated at anaphase as mitosis took place in carpospores, conchocelis filamentous cells, conchosporangial branch cells and sporangial cells (conchospore formation). Chromosome configurations of tetrad and ring-shaped in conchospore germination were observed, demonstrating the occurrence of meiosis. The characteristics of diploid nuclear division in 2n = 6 species are the same as those of 2n = 10 species. The influence of somatic pairing on nuclear division of diploid cells in Porphyra was discussed.