Effects of Methyl Jasmonate on the Composition of Volatile Compounds in <Emphasis Type="Italic">Pyropia yezoensis</Emphasis>

Volatile organic compounds in marine algae have been reported to comprise characteristic flavor of algae and play an important role in their growth, development and defensive response. Yet their biogeneration remain largely unknown. Here we studied the composition of volatile compouds in Pyropia yezoensis and their variations in response to methyl jasmonate (MeJA) and diethyldithiocarbamic acid (DIECA) treatment using gas chromatography-mass spectrometry (GC-MS). A total of 44 compounds belonging to the following chemical classes (n) were identified, including aldehydes (11), alcohols (8), acids and esters (6), alkanes (5), ketones (5), alkenes (3), and S- or N-containing miscellaneous compounds (6). External treatment with plant hormone MeJA increased the content of 1-dodecanol, 4-heptenal, and 2-propenoic acid-2-methyl dodecylester, but decreased the content of phytol, 3-heptadecene, 2-pentadecanone, and isophytol. When pretreated with DIECA, an inhibitor of the octadecanoid pathway leading to the biosynthesis of endogeneous jasmonates and some secondary metabolites, phytol and isophytol were increased, while 4-heptenal, 1-dodecanol, and 2-propenoic acid-2-methyl dodecylester were decreased, both of which were negatively correlated with their variations under MeJA treatment. Collectively, these results suggest that MeJA does affect the volatile composition of P. yezoensis, and the octadecanoid pathway together with endogenous jasmonate pathway may be involved in the biosynthesis of volatile compounds, thereby providing some preliminary envision on the composition and biogeneration of volatile compounds in P. yezoensis.     

Pyropia yezoensis can utilize CO2 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 CO 2 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 signifi cantly 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 CO 2 concentration during moderate dehydration,which might be caused by the enhancement of cyclic electron fl ow.These results suggested that P.yezoensis can directly utilize CO 2 in ambient air during moderate dehydration.     

Defensive physiological characters of Pyropia yezoensis resistant lines to the red rot disease

To explore ef fective physiological indexes to distinguish the resistant lines and susceptible lines of Pyt hium porphyrae,the causal agent of red rot disease of Pyropia yezoensis,and establish the disease-resistance breeding strategy,we obtained and analyzed the candidate resistant and susceptible lines by population selection.Gametophytes of the candidate lines were cultured in seawater containing Pyt.porphyrae zoospores.Antioxidase activities,including superoxide dismutase(SOD),peroxidase(POD) and polyphenol oxidase(PPO),were measured and compared between the two lines before and after infection.In the resistant lines,SOD and POD activities increased and then decreased,but PPO activity rose with the prolongation of the infection time.The phenylalanine ammonia lyase(PAL) activities also increased and then decreased after infection,but it had significantly different expression in the two lines without pathogen attack.The synthesis rates of β-1,3-glucanase,and cell-wall degrading enzyme were different from each other between the two lines after infection of P yt.porphyrae.Comparison in the contents of malondialdehyde(MDA) and reactive oxygen species(ROS) in the two lines showed that,the two contents varied synchronously in response to the pathogen attack.Changes of these enzymes activities or contents demonstrated that Pyr.yezoensis could resist against the pathogen of P yt.porphyrae with the antioxidant defense capacity.In addition,β-1.3-glucanase content showed extremely significant dif ference between the two lines,and the PAL had consistent expression dif ference.Therefore,phenylalanine ammonia lyase(PAL) and β-1,3-glucanase can be considered as an ef fective index to distinguish susceptible line and resistant line,with which the workload of the resistant breeding could be reduced in the future.     

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.     

Development of a PCR method for detection of Pseudoalteromonas marina associated with green spot disease in Pyropia yezoensis

Pseudoalteromonas marina is one of the potential pathogens that cause green spot disease(GSD) in Pyropia yezoensis. To prevent GSD from development and spread, an ef fective method to detect the pathogen at early GSD infection stages need to be established. In this research, PCR methods were established targeting the dnaA gene(encoding chromosome replication initiator protein) and the dnaN gene(encoding β sliding clamp of DNA polymerase Ⅲ protein) to detect P. marina with three primer pairs pws-dnaA 2(Forward, 5′-ACCGCATTAACGAACTACTCGTG-3′; Reverse, 5′-TGCCATTACCTACAGCATGG-3′), pcs-dnaN 2(Forward, 5′-CTTACAACGTTATCAGCGGC-3′; Reverse, 5′-GTTGAGTATTAAGTGATTGAGTAAGC-3′) or pws-dnaN 3(Forward, 5′-ACTTACAACGTTATCAGCGGC-3′; Reverse, 5′-ACTGCTGTTTGAGTCTGCTAAC-3′). Three PCR methods corresponding to the three primer pairs su ? ciently distinguished P. marina from 22 bacterial species, thus resulting in detection limits of 4 to 4×10 2 CFU cells or 2.37×10 1 to 2.37×10 3 fg of P. marina DNA per PCR reaction. In an arti?cial infection experiment of P. yezoensis infected with P. marina, all established PCRs successfully detected P. marina at early GSD infection stages. The results show that the established PCRs are speci?c and sensitive, and are potential for applications in early diagnosis of GSD in Pyropia.     

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.     

Construction of high-density genetic linkage map of Pyropia yezoensis(Bangiales,Rhodophyta) and identification 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.     

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 mitocho ndria).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 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 cro ssed 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.     

Characterization of Pythium chondricola associated with red rot disease of Pyropia yezoensis (Ueda) (Bangiales,Rhodophyta) from Lianyungang,China

Pyropia yezoensis(formerly Porphyra yezoensis) is an economically important red alga that is cultured extensively in China. The red rot disease occurs commonly during Pyropia cultivation,causing serious economic losses. An incidence of red rot disease was found in a P. yezoensis farm from mid-November to mid-December 2015 at Lianyungang, Jiangsu Province, China. Histopathological examination revealed that the naturally infected thalli were infected apparently by a pathogen, leading to red rot symptoms. The causative agent was isolated and identified as the oomycete Pythium chondricola by morphological analysis and sequence analysis of the internal transcribed spacer and cytochrome oxidase subunit 1(cox1). In artificial infection experiments on the P. yezoensis blades, the P. chondricola isolate was able to cause the same characteristic histopathology seen in natural infections. P. chondricola grew well at a wide range of temperatures in the range 8-31℃, salinities at 0-45 and pH 5-9. In an orthogonal test used to determine the effects of environmental factors(temperature, salinity, and zoospore concentration)on infection, the data revealed that temperature was the most important factor to affect red rot disease development, with the optimal conditions for disease expansion being 20℃, 35 salinity, and a zoospore concentration of 10~6 zoospores/mL. The results obtained from the present study prompted us to set up a comprehensive epidemiological study on Pyropia, which will provide support to maintain the healthy development of the Pyropia industry in China.     

Identification of Odor Volatile Compounds and Deodorization of Paphia undulata Enzymatic Hydrolysate

Unfavorable fishy odour is an inevitable problem in aquatic products. In the present study, headspace solid-phase microextraction gas chromatography mass spectrometry(HS-SPME-GC-MS) analysis of volatiles from untreated samples and three deodorized samples(under the optimal conditions) of Paphia undulata enzymatic hydrolysate revealed that the compounds contributing to the distinctive odor were 1-octen-3-ol, n-hexanal, n-heptanal, 2,4-heptadienal, and 2,4-decadienal, whereas n-pentanal, n-octanal, n-octanol, benzaldehyde, 2-ethylfuran and 2-pentylfuran were the main contributors to the aromatic flavor. The deodorizing effects of activated carbon(AC) adsorption, yeast extract(YE) masking and tea polyphenol(TP) treatment on a P. undulata enzymatic hydrolysate were investigated using orthogonal experiments with sensory evaluation as the index. The following optimized deodorization conditions were obtained: AC adsorption(35 mg mL~(-1), 80℃, 40 min), YE masking(7 mg mL~(-1), 45℃, 30 min) and TP treatment(0.4 mg mL~(-1), 40℃, 50 min). AC adsorption effectively removed off-flavor volatile aldehydes and ketones. YE masking modified the odor profile by increasing the relative contents of aromatic compounds and decreasing the relative contents of aldehydes and ketones. The TP treatment was not effective in reducing the odor score, but it significantly reduced the relative content of aldehydes while increasing that of alkanes. It is also notable that TP effectively suppressed trimethylamine(TMA) formation in a P. undulate hydrolysate solution for a period of 72 h.     

Study on cryopreservation of Porphyra yezoensis conchocelis

Cryopreservation of Porphyra yezoensis conchocelis was conducted with cryoprotectants and a proposed pretreatment procedure and thawing methods explored. Six cryoprotectants combined by DMSO with ethylene glycol （EG）, propylene glycol （PEG）, sorbitol and sucrose were developed. The effect of prefreezing at -40℃ or -20℃ for different time durations was compared and the thawing methods were screened. It was shown that the cryoprotectant including 10% DMSO with 0.5 molL^-1 sorbitol exhibited the optimal effect. The ideal pretreatment was that conchocelis segments were stayed for 20min at -40℃ before stored in liquid nitrogen, and 40℃ water bath was proper for quick thawing. The highest recovery rate of cryopreserved P. yezoensis conchocelis reached 89.41%.     

Gamma-rays induction of mutation in conchocelis ofPorphyra yezoensis

Free-living conchocelis ofPorphyra yezoensis Ueda (Bangiales, Rhodophyta) were treated with⁶⁰Co-γ rays of different doses (ranging from 100 Gy to 1000 Gy) to induce mutation. Most of the conchocelis maintained the capability of penetrating into shells, growing and forming colonies in shells, but their vitality was seriously impaired by the irradiation of γ-rays. A few conchocelis pigments were mutagenized directly into different color pigment mutants whose progeny-conchospores and foliose thalli had the same colors. However, some irradiated conchocelis did not show the change in color at the conchocelis stage. The pigment mutation could be observed only after the conchospores of these conchocelis had germinated into young foliose thalli. Irradiation of low dose (100 Gy) promoted the growth of thallus and many with altered morphology were observed. Conchospores of the irradiated conchocelis attached to the culture nets were cultured in the sea, and growth of these progenies was observed and measured.     

Effect of cytokinins and auxins on the growth of free-living conchocelis ofPorphyra yezoensis

IAA 3-Indolylacetic acid, NAA a-Naphthylacetic acid and cytokinins in PESI culture medium were used in a study on the effects of plant hormones on the growth of free-living conchocelis ofPorphyra yezoensis which showed that its growth in medium with cytokinins, IAA and NAA was more rapid than that in medium with non—phytohormones; that the optimal concentrations for promoting growth were 10 μg/L for IAA and ZA (Zeatin), and 0.1 μg/L for BA 6-Benzyl amino purine and KIN 6-Furfurylamino- purine. Mix use of NAA, IAA and cytokinins, NAA/ZA 1–1000/1 μg/L, NAA/BA 10/1-1000 μg/L, NAA/KIN 1/1-1000 μg/L promoted growth. IAA/ZA 0.1-1/0.1-1 μg/L; IAA/BA 0.1-1/0.1-10 μg/L IAA/KIN 1/0.1-1000 μg/L also promoted growth. Contribution No. 2335 from the Institute of Oceanology, Chinese Academy of Sciences. Contribution No. 94 from the Experimental Marine Biology Lab Qingdao, China. The research was supported by a grant from the Chinese Academy of Sciences.     

Effects of elevated CO2 on the photosynthesis and nitrate reductase activity of Pyropia haitanensis (Bangiales,Rhodophyta) grown at different nutrient levels

Pyropia haitanensis,a commercially important species,was cultured at two CO2 concentrations(390×10- 6 and 700×10-6(parts per million)) and at low and high nutrient levels,to explore the effect of elevated CO2 on the species under nutrient enrichment. Results show that in CO2-enriched thalli,relative growth rate(RGR) was enhanced under nutrient enrichment. Elevated CO2 decreased phycobiliprotein(PB) contents,but increased the contents of soluble carbohydrates. Nutrient enrichment increased the contents of chlorophyll a(Chl a) and PB,while soluble carbohydrate content decreased. CO2 enrichment enhanced the relative maximum electronic transport rate and light saturation point. In nutrient-enriched thalli the activity of nitrate reductase(NRA) increased under elevated CO2. An instantaneous pH change in seawater(from 8.1 to 9.6) resulted in reduction of NRA,and the thalli grown under both elevated CO2 and nutrient enrichment exhibited less pronounced reduction than in algae grown at the ambient CO2. The thermal optima of NRA under elevated CO2 and/or nutrient enrichment shifted to a lower temperature(10–15°C) compared to that in ambient conditions(20°C). We propose that accelerated photosynthesis could result in growth increment. Nassimilation remained high in acidified seawater and refl ected increased temperature sensitivity in response to elevated CO2 and eutrophication.     

Effects of Diet on the Volatile Flavor and Nutritional Ingredients of Common Octopus(Octopus vulgaris)

Cephalopods are important economic shellfish that have been developed extensively in the coastal water of various countries. Octopus vulgaris is a large-scaled economic cephalopod that is mainly cultured in South China. This study explored the effect of different diets on the volatile flavor and nutritional ingredients of O. vulgaris. Four diets were tested in four groups: Group A(fish(Scomberomorus niphonius)), Group B(crab(Helice tridens tientsinensis Rathbun)), Group C(clam(Mactra veneriformis)), and Group D(squid(Loligo japonica)). Octopus muscles were sampled after 36 days of feeding, and volatile flavor substances(VFSs), fatty acids(FAs), and amino acids(AAs) were detected. Results showed that the VFSs, FAs, and AAs of octopus in the four groups were obviously different. The sum of volatile ketones and aldehydes was higher in Group B than in the other groups, which could present much more flavors. All groups were abundant in unsaturated FAs, including eicosapentaenoic acid(EPA) and docosahexaenoic acid(DHA). In terms of content and variety, the FAs in Group B were more beneficial to human health than those in the other groups. The content of each AA in Group B was basically higher than those in the other groups and was significantly higher than that in Group D(P < 0.05). Comparing the VFSs, FAs, and AAs in samples fed with four kinds of diets, the results indicate that using crab to feed O. vulgaris can achieve better effects on volatile flavor and nutritional ingredients.     

Identification of Volatile Compounds in Codfish(Gadus) by a Combination of Two Extraction Methods Coupled with GC-MS Analysis

Codfish is a kind of abyssal fish species with a great value in food industry. However, the flavor of codfish, especially the unpleasant odor, has caused serious problems in its processing. To accurately identify the volatile compounds in codfish, a combination of solid phase micro-extraction(SPME) method and simultaneous distillation extraction(SDE) method was used to extract the volatiles. Gas chromatography-mass spectrometry(GC-MS) along with Kovats indices(KI) and authentic standard compounds were used to identify the volatiles. The results showed that a total of 86 volatile compounds were identified in codfish, of them 24 were extracted by SDE, 69 compounds by SPME, and 10 compounds by both SDE and SPME. Seventy volatile compounds were found to have specific odors, of them 7 typical compounds contributed significantly to the flavor of codfish. Alcohols(i.e.,(E)-2-penten-1-ol and 2-octanol), esters(i.e., ethyl butyrate and methyl geranate), aldehydes(i.e., 2-dodecenal and pentadecanal) contributed the most to fresh flavor while nitrogen compounds, sulphur compounds, furans, as well as some ketones(i.e., 2-hydroxy-3-pentanone) brought unpleasant odor, such as fishy and earthy odor. It was indicated that the combination of multiple extraction methods and GC-MS analysis can enhance the accuracy of identification, and provide a reference for the further study on flavor of aquatic products.     

30种中药及其复方对温和气单胞菌的抗菌作用

为评价中药对温和气单胞菌的体外抑菌效果,取鱼腥草、五倍子、黄芩等30种中药,采用水提法制备药液,通过试管二倍稀释法测定各药液对温和气单胞菌的最小抑菌浓度(MIC)及最小杀菌浓度(MBC),筛选出抗菌作用较强的中药作为主药,与牡丹皮、龙胆草、蒲公英等18种中药组成复方,测定中药复方对温和气单胞菌的体外抑制效果。结果表明:五倍子、山茱萸、白芍对温和气单胞菌有较强抑菌活性(MIC≤12.5mg/mL),选取8种主药与清热凉血、清热燥湿、清热解毒药分别组成复方,其中五倍子、诃子、五味子、乌梅与其他多种中药组成的复方抗菌作用增强。     

贮藏时间和加热温度对凡纳滨对虾虾仁ATP关联化合物及品质的影响

【目的】研究贮藏时间和加热温度对凡纳滨对虾(Litopenaeus vannamei)虾仁三磷酸腺苷(ATP)关联化合物及虾仁品质的影响。【方法】利用高效液相色谱法分析凡纳滨对虾中6种ATP关联化合物,通过比较不同贮藏时间的凡纳滨对虾虾仁在加热过程中的ATP关联化合物,分析加热前后虾仁的感官品质,以及鱼虾类鲜度指标K值、G值、P值的变化。【结果与结论】随贮藏时间的增加,ATP、二磷酸腺苷(ADP)、腺苷酸(AMP)含量呈下降趋势,肌苷酸(IMP)先上升后下降,次黄嘌呤(HX)和肌苷(HXR)上升;随着加热温度的增加,ATP和ADP下降,AMP增长,IMP、HX、HXR先增加后降低。贮藏2 d后的生虾和贮藏3 d后再加热的虾仁均将达到最大感官可接受上限。随着贮藏时间的增加,加热前后K值、G值和P值线性增加,但生虾的G值与鲜度的相关性较差,不适宜作为鲜度指标,K值和P值可作为生虾的鲜度指标。加热后的K值、G值、P值与贮藏时间、感官质量评定值(QI值)的线性回归方程的决定系数较好,表明K值、G值、P值可以用来表征熟虾的品质。     

泰莱盆地土壤有机质含量及pH值对微量元素有效性的影响分析

土壤微量元素有效性,对农作物的生长及农产品的品质特征有重要的影响作用。该文首先阐述了泰莱盆地土壤微量元素有效性情况,分析探讨了土壤有机质含量及pH值对泰莱盆地土壤微量养分的有效性影响。结果表明：有效铜、硼和锌的含量有随着土壤中有机质含量增加而增大的趋势;有效硼的含量有随着土壤pH值升高而增大的趋势,有效铁、锰和钼的含量随着pH值的升高逐渐降低。