FAA Composition and Content Variation in Different Pyropia yezoensis Cultivar in Harvest Period

The contents of 16 kinds of free amino acids （FAAs） in 7 Pyropia yezoensis cultivars were determined by pre-column derivatization high performance liquid chromatographyin early, middle and late harvest period.The results showed that the total FAA content ranged from 48.71 to 62.05 mg/g among the 7 test ma- terials. Among the 16 kinds of FAAs, Ala, Arg, Glu and Asp, four kinds of flavor amino acids, showed the highest contents, and their total content ranged from 36.05 to 53.96 mg/g, accounting for 69.11%-86.47% of the total FAA content. The total contents of flavor amino acids and FAAs all reached the peaks in all the test ma- terials, except the control cultivar, at middle harvest period. The essential amino acid content was trended to be increased in all the test materials with the extended harvest period, and it reached the peak at the late harvest period. Sutong showed the highest flavor amino acid content and FAAs content, followed by Y-H002, Suyan and Sulian, while the control cultivar showed the lowest contents.

Pyropia yezoensis can utilize CO_2 in the air during moderate dehydration

Pyropia yezoensis, an intertidal seaweed, experiences regular dehydration and rehydration with the tides. In this study, the responses of P. yezoensis to dehydration and rehydration under high and low CO2 concentrations （（600-700）×10^-6 and （40-80）×10^-6, named Group I and Group II respectively） were investigated. The thalli of Group I had a significantly higher effective photosystem II quantum yield than the thalli of Group II at 71% absolute water content （AWC）. There was little difference between thalli morphology, total Rubisco activity and total protein content at 100% and 71% AWC, which might be the basis for the normal performance of photosynthesis during moderate dehydration. A higher effective photosystem I quantum yield was observed in the thalli subjected to a low CO2 concentration during moderate dehydration, which might be caused by the enhancement of cyclic electron flow. These results suggested that P. yezoensis can directly utilize COz in ambient air during moderate dehydration.

Identification and characterization of a Dna J gene from red alga Pyropia yezoensis(Bangiales, Rhodophyta)

Members of the Dna J family are proteins that play a pivotal role in various cellular processes, such as protein folding, protein transport and cellular responses to stress. In the present study, we identified and characterized the full-length Dna J c DNA sequence from expressed sequence tags of Pyropia yezoensis( Py Dna J) via rapid identification of c DNA ends. This c DNA encoded a protein of 429 amino acids, which shared high sequence similarity with other identified Dna J proteins, such as a heat shock protein 40/Dna J from Pyropia haitanensis. The relative m RNA expression level of Py Dna J was investigated using real-time PCR to determine its specific expression during the algal life cycle and during desiccation. The relative m RNA expression level in sporophytes was higher than that in gametophytes and significantly increased during the whole desiccation process. These results indicate that Py Dna J is an authentic member of the Dna J family in plants and red algae and might play a pivotal role in mitigating damage to P. yezoensis during desiccation.

Involvement of cyclic electron flow in irradiance stress responding and its potential regulation of the mechanisms in Pyropia yezoensis

Pyropia yezoensis, belongs to the genus of P orphyra before 2011, inhabit on intertidal zone rocks where irradiation changes dramatically, implying that the seaweed has gained certain mechanisms to survive a harsh environment. Based on the photosynthetic parameters with or without the inhibitors determined by a Dual-PAM-100 apparatus, we investigated the photosynthetic performance and the changes in electron fl ow that occurred during the algae were stressed with dif ferent light intensities previously. When the irradiation saturation was approaching, the CEF around PS I became crucial since the addition of inhibitors usually led to an increase in non-photochemical quenching. The inhibitor experiments showed that there were at least three dif ferent CEF pathways in Py. yezoensis and these pathways compensated each other. In addition to maintaining a proper ratio of ATP/NAD(P)H to support effi cient photosynthesis, the potential roles of CEF might also include the regulation of dif ferent photoprotective mechanisms in Py. yezoensis. Under the regulation of CEF, chlororespiration is thought to transport electrons from the reduced plastoquinone(PQ) pool to oxygen in order to mitigate the reduction in the electron transfer chain. When irradiation was up to the high-grade stress conditions, the relative value of CEF began to decrease, which implied that the NADP+ pool or PQ + pool was very small and that the electrons were transferred from reduced PS I to oxygen. The scavenging enzymes might be activated and the water-water cycle probably became an ef fective means of removing the active oxygen produced by the irradiation stressed Py. yezoensis. We believe that the dif ferent mechanisms could make up the photoprotective network to allow Py. yezoensis for survival in a highly variable light stress habitat, which may enlighten scientists in future studies on irradiance stress in other algae species.

Characterization,functional properties,and antioxidant activities of macromolecular extracts isolated from Pyropia yezoensis

Pyropia yezoensis is one of the most economical seaweed species in China.Determining how to make full use of mature P.yezoensis and exploring new ways to increase the value of its resources are important subjects of research for the development of the laver breeding industry.In this study,we provide a simple method to comprehensively extract the bioactive substances from P.yezoensis.The characteristics,functional properties,and antioxidant activities of two types of biopolymer extract from P.yezoensis were studied and analyzed relatively.Based on the characterization of water-soluble concentrate(WSC)and alkali-soluble concentrate(ASC),obtained via chemical analysis,including Fourier Transform Infrared Spectrometer(FT-IR)and Thermal Gravimetric Analyzer(TGA),and diff erential scanning calorimetry(DSC),they both had typical polysaccharide and protein characteristics and steady composition.ASC showed higher nitrogen solubility,water holding capacity,and foaming ability.ASC could not only be used as a protein supplement,but also performed well in improving the properties of foods in terms of water holding and fat-absorption.The emulsifying activity and oil-holding capacity of WSC were observed to be higher than those of ASC.Thus,WSC has the potential to be used as an emulsifi er.Surprisingly,WSC and ASC have radical scavenging capacity in vitro,which broadens the direction of their application.

Development of organelle single nucleotide polymorphism (SNP) markers and their application for the identification of cytoplasmic inheritance patterns in Pyropia yezoensis (Bangiales,Rhodophyta)

The genus Pyropia contains several important cultivated species.Genetic research in nori species has mainly focused on the cell nucleus,with few studies on organelles(chloroplast and mitochondria).Due to the high copy numbers of organelles in cells,which influence the development and traits of algae,it is necessary to study their genetic mechanism.In this study,the marine red alga Pyropia yezoensis,an important economic macroalga,was selected as the study object.To investigate organelle(chloroplast and mitochondria)inheritance in P.yezoensis,the wild type RZ(maternal strain)was crossed with the red mutant HT(paternal strain)and 30 color-sectors from 11 F1 gametophytic blades were examined.The complete chloroplast and mitochondrial genomes of the red mutant(HT)were assembled for the first time.One reliable and stable single nucleotide polymorphism(SNP)loci filtrated by bioinformatics analysis was used as a molecular marker for chloroplast and mitochondrial DNA,respectively,in subsequent experiments.PCR amplification and sequence analysis showed that the haplotypes of color-sectors detected were consistent with those of the maternal parent,confirming that both chloroplast and mitochondrial genomes were inherited maternally in P.yezoensis.The inheritance pattern of organelles in P.yezoensis can be used to guide the hybridization and breeding of nori.Additionally,the organelle SNP markers developed in this study can be applied in subsequent genetic research.

Cytological and transcriptional analysis reveal phosphatidylinositol signaling pathway plays key role in mitotic division of Pyropia yezoensis

The phosphatidylinositol(PI)signaling system,a central regulator of eukaryotic metabolism,is widely found in eukaryotes for regulating a variety of cell activities.Most of the genes in the PI signaling system were found conserved in Pyropia yezoensis.In this experiment,wortmannin was used as an inhibitor to inhibit the activity of phosphatidylinositol-3 kinase(PI3K),an important regulator of the PI signaling system.After wortmannin treatment,the mitotic division of P.yezoensis was signifi cantly inhibited in a dose-dependent manner,and the mitotic division percentage was reduced by 68.1%and 91.9%in the 5-and 10-μmol/L groups,respectively.When thalli were treated with wortmannin,the levels of reactive oxygen species(ROS)were signifi cantly decreased.Furthermore,the expression level of PI3K was inhibited and the expression levels of downstream genes regulated by PI3K was signifi cantly changed.In the PI3K-AGC signaling pathway,the expression levels of Serine/threonine protein kinase(AGC)and cyclindependent kinases A(CDKA)were downregulated,while WEE1 kinase gene(WEE1)was upregulated.Three nicotinamide adenine dinucleotide phosphate(NADPH)oxidase genes were downregulated after wortmannin treatment.These results indicate that the PI signaling system plays an important role in the regulation of cell activity in P.yezoensis.It was speculated that the growth and development of P.yezoensis might be regulated by P.yezoensis PI3K,which promoted the expression of the AGC gene and further regulates the expression of downstream WEE1 and CDKA genes to advance mitotic division,and also promoted the expression level of NADPH oxidase that regulates ROS homeostasis.

Construction of high-density genetic linkage map of Pyropia yezoensis(Bangiales,Rhodophyta)and identifi cation of red color trait QTLs in the thalli

Pyropia yezoensis is an important macroalga because of its extensive global distribution and economic importance.Color is an important trait in the thalli of P.yezoensis,it is also an effective marker to identify the hybridization in genetic breeding.In this study,a high-density genetic linkage map was constructed based on high-throughput single nucleotide polymorphism(SNP)markers,and used for analyzing the quantitative trait loci(QTLs)of red color trait in the thalli of P.yezoensis.The conchospore undergoes meiosis to develop into an ordered tetrad,and each cell has a haploid phenotype and can grow into a single individual.Based on this theory,F1 haploid population was used as the mapping population.The map included 531 SNP markers,394.57 cM long on average distance of 0.74 cM.Collinear analysis of the genetic linkage map and the physical map indicated that the coverage between the two maps was 79.42%.Furthermore,QTL mapping identified six QTLs for the chromosomal regions associated with the red color trait of the thalli.The value of phenotypic variance explained(PVE)by an individual QTL ranged from 4.71%-63.11%.And QTL qRed-1-1,with a PVE of 63.11%,was considered the major QTL.Thus,these data may provide a platform for gene and QTL fine mapping,and marker-assisted breeding in P.yezoensis in the future.

Phototropism in the Marine Red Macroalga Pyropia yezoensis

Phototropism is a response to the direction of light that guides growth orientation and determines the shape of plants to optimize photosynthetic activity. The phototropic response is present not only in terrestrial plants but also in water-living algae. However, knowledge about phototropism in Bangiophycean seaweeds is limited. Here, we examined the phototropic response of the red alga Pyropia yezoensis to elucidate the regulatory mechanism of phototropism in Bangiophyceae. When leafy gametophytes and filamentous sporophytes of P. yezoensis were cultured under directional light, phototropism was observed in the gametophytes. Conchosporangia on the sporophytes also exhibited phototropism. Phototropism was positive in the majority of gametophytes and conchosporangia but in some cases was negative. In addition, a strong phototropic response occurred under white light, whereas blue and red light elicited minor and no responses, respectively. This observation is in contrast with the phototropic response in terrestrial plants and several algae, in which blue light is responsible for positive phototropism. Surprisingly, the genome of P. yezoensis has no homologues of the photoreceptors for blue and red light, revealing differences in the regulation of phototropism between terrestrial plants and P. yezoensis . Studies on the phototropism in P. yezoensis could shed light on the evolutional divergence of phototropic responses in plants.

Isolation and characterization of a heat-resistant strain with high yield of Pyropia yezoensis Ueda(Bangiales,Rhodophyta)

A heat-resistant Pyropia yezoensis strain YZ-4 was isolated from the regenerated blades of single somatic cells of the wild-type(WT)blades treated with 60Co-g-irradiation.When cultured at 23
C and 24
C,the survival and division rates of the YZ-4 conchospores were significantly higher than those of WT(P<0.01).After 16 days in culture the survival rates of YZ-4 conchospores were 71.2%and 60.8%at 23
C and 24
C,respectively,and the division rates of the surviving conchospores were 100%in both cases.Under the same culture conditions,the survival rates of WT conchospores were only 16.9%and 11.5%,and the division rate 99.8%and 81.8%respectively.The resistance of 50-day-aged F1 gametophytic blades of YZ-4 to the temperature rebound was also significantly higher than those of WT(P<0.01).After 30 days in culture at 18
C,23
C and 24
C,the mean blade length increased by 8.5,4.3 and 2.3 times in YZ-4 and was only 3,0.6 and 0.4 times in WT,respectively.The mean blade weight increased 191.9,85.4 and 66.2 times in YZ-4,but only 78.2,7.8 and 4.6 times in WT.On the 15th day WT blades began to decay,but no decay was observed in YZ-4 blades even after 45 days in culture at 23
C and 24
C.The results obtained indicate that YZ-4 has a higher resistance to higher temperature insults than WT and it might be of value for commercial production of P.yezoensis.

Discrepancy in photosynthetic responses of the red alga Pyropia yezoensis to dehydration stresses under exposure to desiccation,high salinity,and high mannitol concentration

Macroalgae that inhabit intertidal zones are exposed to the air for several hours during low tide and must endure desiccation and high variations in temperature, light intensity, and salinity. Pyropia yezoensis (Rhodophyta, Bangiales), a typical intertidal red macroalga that is commercially cultivated in the northwestern Pacific Ocean, was investigated under different dehydration stresses of desiccation, high salinity, and high mannitol concentration. Using chlorophyll fluorescence imaging, photosynthetic activities of P. yezoensis thalli were analyzed using six parameters derived from quenching curves and rapid light curves. A distinct discrepancy was revealed in photosynthetic responses to different dehydration stresses. Dehydration caused by exposure to air resulted in rapid decreases in photosynthetic activities, which were always lower than two other stresses at the same water loss (WL) level. High salinity only reduced photosynthesis significantly at its maximum WL of 40% but maintained a relatively stable maximum quantum yield of photosystem II (PSII) (Fv/Fm). High mannitol concentration induced maximum WL of 20% for a longer time (60 min) than the other two treatments and caused no adverse influences on the six parameters at different WL except for a significant decrease in non-photochemical quenching (NPQ) at 20% WL. Illustrated by chlorophyll fluorescence images, severe spatial heterogeneities were induced by desiccation with lower values in the upper parts than the middle or basal parts of the thalli. The NPQ and rETRmax (maximum relative electron transport rate) demonstrated clear distinctions for evaluating photosynthetic responses, indicating their sensitivity and applicability. The findings of this study indicated that the natural dehydration of exposure to air results in stronger and more heterogeneous effects than those of high salinity or high mannitol concentration.

不同温度和光强对条斑紫菜生长和光合生理的影响

条斑紫菜(Pyropia yezoensis)是一种具有重要经济价值的海藻。该研究旨在探究不同温度和光照强度条件对其生长和光合生理的影响。实验设置了低温(LT:10℃)和高温(HT:14℃)以及不同自然光光照强度(50%、25%、12.5%、6.25%、3.125%)的条件,以研究温度和光照强度对条斑紫菜生长和光合生理指标的影响。研究结果表明,在低温条件下,强光显著抑制了条斑紫菜的生长;而在较高温度下,低光则限制了其生长。高温和低光条件均显著抑制了条斑紫菜的最大量子产量(Fv/Fm)。较低的光强有利于光合色素叶绿素a(Chl a)、类胡萝卜素(Car)、藻红蛋白(PE)和藻蓝蛋白(PC)的积累,弱光条件以及较高温度条件下的中等光强适合Chl a和Car的积累,而较低的温度和较弱的光强则促进了PE和PC的合成。综上所述,温度和光照强度显著影响条斑紫菜的生长和光合生理指标,并对其各种光合色素的积累具有交互作用。