Search Results (13)

Neopyropia yezoensis, a marine red algae species, has significant economic and ecological value. However, phosphorus (P) deficiency has emerged as a growing concern in many cultivation regions, negatively impacting its growth. To adapt to P deficiency, algae have evolved various strategies, including using dissolved organic phosphorus (DOP) sources to sustain growth. Despite its prevalence as a form of DOP, the utilization mechanism of glucose-6-phosphate (G6P) by N. yezoensis remains unclear. In this study, the physiological and transcriptional responses of N. yezoensis to P deficiency and G6P supplementation were examined. The results demonstrated that prolonged P deficiency significantly inhibited the growth of N. yezoensis and had a negative impact on physiological indicators such as photosynthetic pigments and antioxidant enzyme activity. However, G6P treatment gradually alleviated these adverse effects over time. Both P deficiency and G6P treatment were associated with increased expression of genes involved in signal transduction and P starvation responses while concurrently downregulating genes related to photosynthesis and antioxidant defenses. In contrast, the suppression of gene expression was less significant under G6P treatment. This study elucidates the adaptive strategies of N. yezoensis in response to P deficiency and clarifies the regulatory pathways involved in G6P utilization, providing novel insights into its P nutrient acquisition and metabolic regulation. Full article

Betaine structural analogs are compounds characterized by the presence of positive and negative charges in a single molecule and have been reported to have physiological properties, such as anti-inflammatory activities. In this study, we performed a metabolomic analysis of metabolite composition changes during the fermentation of Neopyropia yezoensis, an edible red alga, with Aspergillus oryzae for 72 h. The results indicated that three specific betaine structural analogs (betaine, stachydrine, and carnitine) exhibited significant changes in production by the end of the 72 h fermentation period. Time-course analysis suggested that betaine was generated from the precursor choline at 12–24 h during the late stage of fungal growth, while stachydrine was generated from the precursor-related compound glutamic acid at 48–72 h during the sporulation stage. However, the contribution of the precursor lysine to the increased production of carnitine during the 12–72 h period was unclear. This study provides useful information on the efficient production of betaine structural analogs by the fungal fermentation of seaweed as well as various other food materials. Full article

Heat shock protein 70 (HSP70) is an evolutionarily conserved protein chaperone in prokaryotic and eukaryotic organisms. This family is involved in the maintenance of physiological homeostasis by ensuring the proper folding and refolding of proteins. The HSP70 family in terrestrial plants can be divided into cytoplasm, endoplasmic reticulum (ER)-, mitochondrion (MT)-, and chloroplast (CP)-localized HSP70 subfamilies. In the marine red alga Neopyropia yezoensis, the heat-inducible expression of two cytoplasmic HSP70 genes has been characterized; however, little is known about the presence of other HSP70 subfamilies and their expression profiles under heat stress conditions. Here, we identified genes encoding one MT and two ER HSP70 proteins and confirmed their heat-inducible expression at 25 °C. In addition, we determined that membrane fluidization directs gene expression for the ER-, MT-, and CP-localized HSP70 proteins as with cytoplasmic HSP70s. The gene for the CP-localized HSP70 is carried by the chloroplast genome; thus, our results indicate that membrane fluidization is a trigger for the coordinated heat-driven induction of HSP70 genes harbored by the nuclear and plastid genomes in N. yezoensis. We propose this mechanism as a unique regulatory system common in the Bangiales, in which the CP-localized HSP70 is usually encoded in the chloroplast genome. Full article

To investigate the potential influences of nutrients and solar irradiance of the sea area on the laver industry, Neopyropia yezoensis samples and the corresponding surface water were collected at different sites in Haizhou Bay and the Jimo aquafarm, and the solar irradiance was recorded on-site. Then the cellular compositions and the nutrients of seawater were determined. A comparative experiment was also designed to investigate the effect of strong light on the cellular composition of N. yezoensis. Gray correlation analysis showed that the seawater nutrient levels and solar irradiance had a similar correlation degree of 0.6 to 0.8, which indicated similar effects on algal cellular composition. Compared with those samples collected from Haizhou Bay, the algae cultivated at the Jimo aquafarm had higher contents of total protein and hydrolyzable polysaccharides. In addition, the content of chlorophyll a was relatively lower and that of β-carotene higher in the early-stage samples. The results of the comparative experiment showed that the decrease in light intensity on algae promoted the synthesis of chlorophyll a and R-phycoerythrin. It is speculated that the nutrient deficiency in the seawater and the resulting high transparency of the water make the algae more exposed to strong light conditions. This may be the reason for the poor glossiness and hardness of the laver products made from the cultivated algae in the north Yellow Sea. Thus, it puts forward specific requirements for the modification of N. yezoensis cultivation techniques in the north Yellow Sea. Full article

The red alga Neopyropia yezoensis undergoes polarized elongation and asymmetrical cell division of the apical stem cell during tip growth in filamentous generations of its life cycle: the conchocelis and conchosporangium. Side branches are also produced via tip growth, a process involving the regeneration and asymmetrical division of the apical stem cell. Here, we demonstrate that auxin plays a crucial role in these processes by using the auxin antagonist 2-(1H-Indol-3-yl)-4-oxo-4-phenyl-butyric acid (PEO-IAA), which specifically blocks the activity of the auxin receptor TRANSPORT INHIBITOR RESPONSE1 (TIR1) in land plants. PEO-IAA repressed both the regeneration and polarized tip growth of the apical stem cell in single-celled conchocelis; this phenomenon was reversed by treatment with the auxin indole-3-acetic acid (IAA). In addition, tip growth of the conchosporangium was accelerated by IAA treatment but repressed by PEO-IAA treatment. These findings indicate that auxin regulates polarized tip cell growth and that an auxin receptor-like protein is present in N. yezoensis. The sensitivity to different 5-alkoxy-IAA analogs differs considerably between N. yezoensis and Arabidopsis thaliana. N. yezoensis lacks a gene encoding TIR1, indicating that its auxin receptor-like protein differs from the auxin receptor of terrestrial plants. These findings shed light on auxin-induced mechanisms and the regulation of tip growth in plants. Full article

As an economically valuable red seaweed, Neopyropia yezoensis (Rhodophyta) is cultivated in intertidal areas, and its growth and development are greatly influenced by environmental factors such as temperature. Although much effort has been devoted to delineating the influence, the underlying cellular and molecular mechanisms remain elusive. In this study, the gametophyte blades and protoplasts were cultured at different temperatures (13 °C, 17 °C, 21 °C, 25 °C). Only blades cultured at 13 °C maintained a normal growth state (the relative growth rate of thalli was positive, and the content of phycobiliprotein and pigments changed little); the survival and division rates of protoplasts were high at 13 °C, but greatly decreased with the increase in temperature, suggesting that 13 °C is suitable for the growth of N. yezoensis. In our efforts to delineate the underlying mechanism, a partial coding sequence (CDS) of Cyclin B and the complete CDS of cyclin-dependent-kinase B (CDKB) in N. yezoensis were cloned. Since Cyclin B controls G2/M phase transition by activating CDK and regulates the progression of cell division, we then analyzed how Cyclin B expression in the gametophyte blades might change with temperatures by qPCR and Western blotting. The results showed that the expression of Cyclin B first increased and then decreased after transfer from 13 °C to higher temperatures, and the downregulation of Cyclin B was more obvious with the increase in temperature. The phosphorylation of extracellular signal-regulated kinase (ERK) decreased with the increase in temperature, suggesting inactivation of ERK at higher temperatures; inhibition of ERK by FR180204 significantly decreased the survival and division rates of protoplasts cultured at 13 °C. These results suggest that downregulation of Cyclin B and inactivation of ERK might be involved in negatively regulating the survival and division of protoplasts and the growth of gametophyte blades of N. yezoensis at high temperatures. Full article

Laver is a popular food for its high nutritional value, which can change among culture areas and along with the progression of harvest. Neopyropia yezoensis and Neoporphyra haitanensis were cultured in succession in Taoluo and Muping, north China. The chemical composition of laver samples together with some ecological factors in the farms were investigated. From September to December, salinity increased while water temperature decreased in both areas. Dissolved inorganic nitrogen (DIN) and N:P decreased in Taoluo while increasing in Muping. Both N. yezoensis and N. haitanensis contained high levels of protein (26.90–41.38% DW) and low contents of fat (0.36–0.74% DW). High levels of minerals were detected in both species. The contents of protein, total amino acids, and total minerals in N. haitanensis increased significantly, while sugar content decreased significantly from September to December. The gray correlation analysis result implied that the typical ecological factors (DIN, dissolved inorganic phosphorus, N:P, pH, salinity, temperature, and transparency) have a great influence on accumulation of the crude nutrient, amino acid, fatty acid components, and mineral components in laver. The coefficient of variation analysis result also showed that environmental heterogeneity obviously enhanced differences in the contents of protein, amino acid, and trace elements in N. yezoensis. In addition, the principal component analysis result showed that the N. yezoensis strain ‘Huangyou No. 1’ had the highest comprehensive evaluation score in the four tested N. yezoensis strains, indicating that it has the best comprehensive quality and greatest exploitable value. We hope these findings will help to improve future laver breeding and farming. Full article

Seaweeds are important to marine ecosystems through biogeochemical processes. Laver are the most widely farmed seaweeds with the largest culture area in China. This study analyzes the water quality characteristics in a large-scale laver culture area (Taoluo) by comparing a small-scale laver culture area and non-culture areas, thereby assessing the changes in water quality due to large-scale laver cultivation. Particulate organic carbon and/or dissolved organic carbon decreased while the total suspended solid increased seasonally or with the distance from the coast. The concentrations of total nitrogen as well as dissolved inorganic nitrogen and phosphorus were generally higher near the shore and decreased seasonally in Taoluo. Substantial spatial variation in nutrient parameters between culture and non-culture sites was observed. Moreover, significant variations between culture and non-culture sites on a spatio-temporal scale were mostly observed in December compared with September and October. Furthermore, more clusters were found in December based on the water quality characteristics in various sampling sites using a hierarchical clustering analysis. These results suggested that more spatial deviation in water quality parameters between culture and non-culture sites were found in December; thus it can be hypothesized that the changes in water quality due to large-scale cultivation for laver was likely to occur in northern China in winter, i.e., the period of best growth status for the cold-temperate species of laver (e.g., Neopyropia yezoensis). We hope that this study can help to further understand the effects of seaweed farming on marine environments. Full article

Heat stress responses are complex regulatory processes, including sensing, signal transduction, and gene expression. However, the exact mechanisms of these processes in seaweeds are not well known. We explored the relationship between membrane physical states and gene expression in the red alga Neopyropia yezoensis. To analyze heat-stress-induced gene expression, we identified two homologs of the heat-inducible high temperature response 2 (HTR2) gene in Neopyropia seriata, named NyHTR2 and NyHTR2L. We found conservation of HTR2 homologs only within the order Bangiales; their products contained a novel conserved cysteine repeat which we designated the Bangiales cysteine-rich motif. A quantitative mRNA analysis showed that expression of NyHTR2 and NyHTR2L was induced by heat stress. However, the membrane fluidizer benzyl alcohol (BA) did not induce expression of these genes, indicating that the effect of heat was not due to membrane fluidization. In contrast, expression of genes encoding multiprotein-bridging factor 1 (NyMBF1) and HSP70s (NyHSP70-1 and NyHSP70-2) was induced by heat stress and by BA, indicating that it involved a membrane-fluidization-dependent pathway. In addition, dark treatment under heat stress promoted expression of NyHTR2, NyHTR2L, NyMBF1, and NyHSP70-2, but not NyHSP70-1; expression of NyHTR2 and NyHTR2L was membrane-fluidization-independent, and that of other genes was membrane-fluidization-dependent. These findings indicate that the heat stress response in N. yezoensis involves membrane-fluidization-dependent and -independent pathways. Full article

Edible algae Neopyropia yezoensis is used as “Nori”, its dried sheet product, in Japanese cuisine. Its lipid components reportedly improve hepatic steatosis in obese db/db mice. In this study, we prepared “Nori powder (NP)” and “fermented Nori powder (FNP)” to utilize the functional lipids contained in “Nori” and examined their nutraceutical effects in vivo. Male db/db mice were fed a basal AIN-76 diet, a 10% NP-supplemented diet, or a 10% FNP-supplemented diet for 4 weeks. We detected eicosapentaenoic acid (EPA) present in both NP and FNP in the serum and liver of db/db mice in a dose-dependent manner. The NP diet reduced hepatic triglyceride accumulation (by 58%) in db/db mice by modulating gene expression, which resulted in the inhibition of lipogenic enzyme activity. Additionally, NP intake significantly suppressed the expression of inflammatory genes in the liver and hepatic injury marker levels in the sera (by 26%) of db/db mice. The FNP diet also led to a marked reduction in hepatic triglyceride accumulation (by 50%) and hepatic injury (by 28%) in db/db mice, and the mechanism of these alleviative actions was similar to that of the NP diet. Although the EPA content of FNP was one-third that of NP, metabolomic analysis revealed that bioactive betaine analogs, such as stachydrine, betaine, and carnitine, were detected only in FNP. In conclusion, we suggest that (1) mechanical processing of “Nori” makes its lipid components readily absorbable by the body to exert their lipid-lowering effects, and (2) fermentation of “Nori” produces anti-inflammatory molecules and lipid-lowering molecules, which together with the lipid components, can exert hepatic steatosis-alleviating effects. Full article

Neopyropia yezoensis is an economically important marine crop that can survive dehydrating conditions when nets are lifted from seawater. During this process, production of oxygen radicals and the resulting up-regulation of antioxidant enzymes mediated by the abscisic acid (ABA) signaling pathway played an important role. However, there were no reports about the significance regarding the protection of seaweed throughout the entire production season. Especially, in new aquatic farms in Shandong Province that were formed when traditional N. yezoensis cultivation moved north. Here, we determined the levels of ABA, hydrogen peroxide (H₂O₂), soluble protein, chlorophyll, and cell wall polysaccharides in samples collected at different harvest periods from Jimo aquatic farm, Shandong Province. The activities and expression of NADPH oxidase (NOX) and antioxidant enzymes in the corresponding samples were also determined. Combined with the monitoring data of sea surface temperature and solar light intensity, we proposed that the cultivation of N. yezoensis in Shandong Province was not affected by high-temperature stress. However, photoinhibition in N. yezoensis usually occurs at noon, especially in March. Both the activities and the expression of NOX and antioxidant enzymes were up-regulated continuously. It is reasonable to speculate that the reactive oxygen species (ROS) produced by NOX induced the up-regulation of antioxidant enzymes through the ABA signaling pathway. Although antioxidant enzymes play a pivotal role during the cultivation of N. yezoensis, the production of ROS also caused a shift in gene expression, accumulation of secondary metabolites, and even decreased the chlorophyll pool size, which eventually led to a decrease in algae assimilation. Accordingly, we suggest that the dehydration of N. yezoensis nets should be adopted when necessary and the extent of dehydration should be paid special consideration to avoid an excessive cellular response caused by ROS. Full article

Extracellular matrix (ECM) proteins play crucial roles in the regulation of cell proliferation and differentiation. We identified homologous genes encoding ECM proteins that are known to associate with integrins in animal cells in red macroalga Neopyropia yezoensis. Four genes encoding spondin domain-containing proteins (NySPLs) and eight genes encoding fasciclin domain-containing proteins (NyFALs) from N. yezoensis were selected for bioinformatics and expression analysis in order to obtain insights into the roles of ECM proteins for the life cycle. NySPLs had eight β-strands with two contiguous α-helices, which were similar to those of the F-spondin domain of animals. NyFALs had conserved H1 and H2 motifs and a YH motif between the H1 and H2 regions. Quantitative reverse transcription polymerase chain reaction showed that NySPL1–3 and NyFAL8 transcripts were highly accumulated in mature gametophytes that formed the spermatia. Furthermore, expressions of all NySPLs were upregulated in response to the ethylene precursor 1-aminocylopropane-1-carboxylic acid that induces gametogenesis. NyFAL1, 4 were highly expressed in sporophytes, whereas NyFAL2, 3, 5, 6, and 7 were overexpressed in gametophytes, especially at the vegetative stage. These findings facilitate future research on ECM architecture in the unique life cycles of red macroalgae. Full article

Gametophyte-to-sporophyte transition in the haploid-diploid life cycle depends on fertilization of male and female gametes. We describe here a mutant of the marine red seaweed Neopyropia yezoensis, designated akasusabi (aks), where the gametophyte-to-sporophyte transition occurs independently of fertilization. Although conchocelis filaments were produced from carpospores, severe defects in the maturation of carposporangia via mitosis to generate conchospores were observed. In the aks mutant, however, somatic cells of gametophytic thalli were able to produce conchocelis filaments without fertilization. Thus, apogamy occurs in aks. In addition, aks was highly sensitive to wounding that promotes both asexual and apogamous reproductive responses by producing spores, which develop either into blades or conchocelis filaments, indicating that aks responds to wounding by enhanced reproduction. These findings indicated that the aks mutation enables the transformation of vegetative cells to carpospores to produce sporophytes by apogamy and wound-inducible life cycle trade-off, stimulating a reset of the timing of reproduction during the life cycle. Therefore, AKS is involved in regulations of the gametophyte-to-sporophyte transition and asexual spore production in N. yezoensis. Full article