Oyster studies reveal the duplication and functional diversification of Bivalvia caspase-8 genes

Caspase-8,first classified as a pro-apoptotic caspase,is considered to have arisen from duplication with caspase-10 and involves multiple immune and inflammatory responses in mammals.However,few are known on the phylogeny and function of caspase-8 in molluscs,one of the largest phyla in marine invertebrates.In this study,we conducted phylogenetic and functional analysis on molluscan caspase-8-like genes.Results indicate that duplication occurred in molluscan caspase-8-like genes,resulting in at least two caspase-8 copies in some groups of bivalves.Additional studies in Pacific oyster Crassostrea gigas showed different spatio-temporal expression patterns and subcellular localizations of CgCaspase-8-1 and CgCaspase-8-2.While no interaction was observed between CgCaspase-8-2 and CgFADD,the adaptor molecule in apoptosis,yeast two-hybrid and co-immunoprecipitation assays suggested the interaction between CgCaspase-8-1 and CgFADD,indicating its pro-apoptotic function.In addition,CgCaspase-8-1 showed interaction with the CARD domain of CgRIG-I.Together with two NF-κB subunits(Cgp105 and CgRel),their transcripts were up-regulated in response to poly(I:C)stimuli,supporting the immune function of both pro-and anti-inflammation.The results provide insight into the evolution and functional diversification of Bivalvia caspase-8 genes.

Effect of high light and desiccation on photosystem Ⅱ in the seedlings and mature plants of tropical seagrass Enhalus acoroides during low tide

During low tide,the intertidal seagrass Enhalus acoroides is often exposed to high light and desiccation,which can seriously threaten its survival,at least partly by inhibiting photosystem Ⅱ(PSⅡ)activity.The response of leaves of E.acoroides to high light and desiccation was compared for seedlings and mature plants.Results show that the resistance of seedling and mature leaves to high light was quite similar,but to desiccation was very different.Seedling leaves were more sensitive to desiccation than the mature plant leaves,but had better water retention.The damage of desiccation to seedling leaves was mainly caused by dehydration,whereas that to mature plant leaves was caused by hypersaline toxicity.The recovery rate of PSⅡ of seedling leaves was significantly slower than that of the mature plants after the stresses disappeared,which may at least partly contribute to seedling mortality in the wild.In addition,compared to high light,desiccation seriously inhibited the recovery rate of PSⅡ activities even if the leaves became fully rehydrated to their normal relative water content(RWC)in the following re-immersion.Desiccation inhibited the recovery rate of RC/CS_(M)(reaction center per cross section(at t=t_(Fm)))to decrease the production of assimilatory power,which maybe the cause of the slower PSⅡ recovery in desiccation treatments.This study demonstrates that desiccation particularly coupling with high light have a very negative ef fect on the PSⅡ of E.acoroides during low tide and the sensitivity of seedlings and mature plants to desiccation is significantly different,which have important reference significance to choose an appropriate transplanting depth where seedlings and mature plants of E.acoroides not only receive sufficient light for growth,but also that minimize desiccation stress during low tide.

Molecular identification,expression pattern,and in-vitro bioactivity analysis of insulin-like growth factor 2 in olive flounder Paralichthys olivaceus

Insulin-like growth factors(IGFs)are key regulators of development and growth.Here,we characterized the igf2 gene from olive flounder(Paralichthys olivaceus)and determined its temporal and spatial expression.We set up an in-vitro protein expression system in eukaryotic human embryonic kidney(HEK293 T)cells and explored its effects on cell proliferation.The flounder igf2 cDNA contained a 648-bp open reading frame(ORF)encoding a protein of 215 amino acids(aa),which spanned the complete signal peptide(47 aa),mature peptide(70 aa),and E domain(98 aa).In adult flounder,igf2 mRNA was detected in all selected tissues.In early development,igf2 mRNA was detected throughout development from unfertilized eggs to hatching-stage embryos.In-situ hybridization analysis indicated that igf2 mRNA was specially expressed in the brain region,floor plate,hypochord,otic vesicle,and pectoral fin during embryogenesis.Western blotting analysis indicated that the soluble recombinant flounder IGF2 protein was successfully produced through eukaryotic expression in HEK293T cells.In addition,the recombinant IGF2 protein significantly promoted the proliferation of human cervical carcinoma(HeLa)and HEK293T cells.These results provide new information about the structural and functional conservation,expression patterns,and biological activity of the igf2 in teleosts.

Shell characterization and effects on cavity volume of wild Jinjiang oyster Crassostrea ariakensis in different estuaries of China

Jinjiang oyster Crassostrea ariakensis,a species with economic and ecological value,is distributed along the estuaries and coasts of East Asia.With the decline in natural resources,the conservation and aquaculture of this species is urgent.However,studies characterizing their shell shape remain scarce.We investigated the morphological differences in the shells of wild Jinjiang oysters from six populations(Qinzhou,Shanghai,Nantong,Qingdao,and Binzhou hard or muddy bottom)along the coast of China.The color of the shell and adductor muscle scar showed associations with temperature gradient along its geographical distribution.Oyster shape was defined by shell height to shell length ratio,and the ratio varies among geographic locations of the populations.They were found nearly round(Qinzhou and Nantong populations),oval(Qingdao and Binzhou populations),or water-droplet-shaped(Shanghai population).Binzhou populations living on muddy substrates are more elongated than those on hard substrate.In addition,we developed a method to measure the cavity volume in oysters.Correlation and path analysis showed that shell height significantly influenced cavity volume.The synergistic effect of the two factors(the height,length,and width of the shell in pairs)on the cavity volume resulted in differences between northern and southern groups:samples from the southern group(Qinzhou and Shanghai)showed correlation between shell height and shell width,while those from the northern group(Nantong,Qingdao,and Binzhou)showed correlation between shell height and shell length.All populations showed significant correlation between shell height and cavity height,and shell length and cavity length,while the correlation between shell width and cavity width was minimal,which may have been resulted from uneven shell thickness.The linear equation for shell height and cavity volume under different ratios of shell height to length was obtained.In this study,we determined that shell height has the most influence on cavity volume,and specific cavity volume fitting linear equations are given for different shell types,which may provide a reference for future oyster breeding for shell shaping.

Discovery of prenylated indole alkaloid and natural xanthone from cold-seep sediment derived fungus Talaromyces funiculosus SD-523

A new prenylated indole alkaloid 11,17-epi-mangrovamide A(1),a new natural occurring product,1,7-dihydroxy-6-methyl-8-hydroxymethyl-xanthone(2),two known alkaloids,mangrovamide A(3)and mangrovamide G(4),and four known polyketide derivatives(5–8)were isolated and identified from the cold-seep sediment derived fungal strain Talaromyces funiculosus SD-523.Their structures were elucidated by combination of nuclear magnetic resonance(NMR),high resolution electrospray ionization mass spectroscopy(HRESIMS),quantum chemical electronic circular dichroism(ECD),and DP4+probability analysis as well as by comparison of the data with literature reports.All isolated compounds were tested for antibacterial activities.

Vertical microbial profiling of water column reveals prokaryotic communities and distribution features of Antarctic Peninsula

Prokaryotic diversity and community composition in the water column of eight stations(63 samples) around the Antarctic Peninsula of the Southern Ocean were investigated. Through pyrosequencing of the V3–V4hypervariable regions of the 16S ribosomal RNA gene, we characterized 4 720 089 valid reads representing 48 188operational taxonomic units(OTUs, 97% similarity). The community was dominated by the phyla Pseudomonadota(original name: Proteobacteria, 47%), Oxyphotobacteria(26%), and Bacteroidota(original name: Bacteroidetes, 18%), which comprised an average of 91% of the total OTUs in all samples. The prokaryotic community composition varied vertically within the water column. Water column prokaryotic communities exhibited a clear depth profile, with higher microbial richness and higher diversity observed with increasing water depth. Cluster analysis of the community composition of water column samples exhibited a similar trend with depth. Correlation with environmental factors suggested distinct variation in prokaryotic community composition with changes in depth, salinity, temperature and dissolved oxygen levels. Functional prediction showed presence of active nitrogen, sulphur and methane metabolic cycles along the vertical transect of the studied region. These results will improve our knowledge of prokaryotic diversity and community composition at different depth of water column for better understanding of the microbial ecology and nutrient cycles in Antarctic Peninsula region of the Southern Ocean.

Potential of Ulva prolifera in phytoremediation of seawater polluted by cesium and cobalt: an experimental study on the biosorption and kinetics

Radionuclides accidentally released from nuclear power plants,such as ^(137)Cs and ^(60)Co,can lead to severe contamination of marine ecosystems.Living macroalgae are effi cient in absorbing metal elements from seawater.A 10-day simulation was conducted to assess the potential of scavenging cesium(Cs)and cobalt(Co)with live U lva prolifera that was cultured in seawater medium containing Cs and Co in diff erent concentrations(0(the control),10,20,50,and 100 mg/L).In the experiment,5 kg(fresh weight)of U.prolifera was cultured in natural seawater in 90-L tanks.Results showed that after the experiment,the average bioconcentration factors(BCFs)of the control group were 247.2 and 1126.4 for Cs and Co,respectively.The absolute absorption quantity of U.prolifera increased and the BCFs decreased with the increase in Cs and Co concentrations.The biosorption of the two metals on the fi rst day well fi t the pseudo-second-order equation(R^(2)>0.95),indicating that adsorption is the rate-limiting step in the total biosorption process.Concentrations of both metal ions declined signifi cantly in the fi rst hour and decreased by 25.2%and 15.5%in 48 h,respectively.Therefore,live U.prolifera is effi cient at scavenging Cs and Co in seawater,providing potential applications for the phytoremediation of radionuclides contaminated seawaters.

Impact of ocean acidification on physiology and microbiota in hepatopancreas of Pacific oyster Crassostrea gigas

The hepatopancreas is an important tissue involved in various biological metabolism for mollusks,but its responses to ocean acidifi cation(OA)have not been well evaluated.In this study,the oysters were cultured in simulated conditions by continuously bubbling with ambient air(pH=8.10)or air-CO_(2)(pH=7.50)for up to two months,and the variations on the antioxidant capacity,digestive ability,and microbiota composition in hepatopancreas of Crassostrea gigas were analyzed.The results show that although superoxide dismutase and glutathione responded quickly to OA stress,the antioxidant capacity of the hepatopancreas was inhibited,as revealed by the decrease of the total antioxidant capacity,which led to an upward trend of the malondialdehyde,demonstrating that the oxidative damages were accumulated under the OA process.The determination of the digestive ability manifested as the decrease of pepsin activity and the recovery of lipase and amylase activity after long-term acidifi cation,which may be helpful to improve the adaptability of oysters.In addition,analysis on 16S rDNA amplicon revealed that the total species abundance and diversity of the hepatopancreas microbiota experienced a dynamic change,but fi nally it decreased greatly after long-term acidifi cation.The structure of the hepatopancreas microbiota was changed drastically with the change of the dominant species from aerobic to the anaerobic and facultative anaerobic bacteria,and the abnormal proliferation of some species,such as genus of Mycoplasma and order Clostridiales,which may aggravate the adverse eff ects of OA on the physiological functions of the hepatopancreas.As a result,our fi ndings enrich our understanding of the accumulated oxidative damage and adaptive digestive ability in oyster hepatopancreas caused by OA.For the fi rst time,the changes of the hepatopancreas microbiota under long-term acidifi cation conditions are described,proving a good reference for the study of the response and adaptation mechanisms of bivalve mollusks in a wide range of oceans OA.

First record of Ulva californica in the mainland of China:a single alien parthenogenetic population in discontinuous distribution

Molecular investigations have raised concerns about the ecological risks of green tides caused by alien Ulva species in new habitats.The green tide-forming species U.californica Wille was generally considered to be native to North America,but new records have been widely reported in Europe,Asia,and Oceania in recent decades,indicating a strong dispersal capacity of the species.In this study,the first record of U.californica on the coastline of China's Mainland was reported,following a combined identification with multi-molecular markers and morphological characterization.It was shown that this species has a discontinuous distribution pattern along the coast of China's Mainland,with northern populations in the Yellow Sea and southern populations in the East China Sea and South China Sea.According to results of examination for life cycles and identification with mating type(MT)genetic markers,it was indicated that all U.californica samples were male gametophytes,and reproduced themselves through parthenogenesis solely.Combined with the fact that southern and northern populations are highly genetically identical,here we believed that U.californica was a recent alien species to China's Mainland with a rapid local spread.This finding provided evidences that the ability to reproduce in a variety of ways may play an important role in the spread of Ulva species,as well as essential basic data for marine risk management of green tides in China.In addition,according to the phylogeographic analysis,the possible geographical origin and global dispersal routes of U.californica were also proposed.

Multiple Isoforms of Olive Flounder (Paralichthys olivaceus) Pax3a and Pax3b Display Differential Regulations on Myogenic Differentiation

Paired box 3(Pax3)is a critical upstream regulator of the onset of myogenesis.We have previously identified two spliced isoforms of pax3a(pax3a-1 and pax3a-2)and three spliced isoforms of pax3b(pax3b-1,pax3b-2,and pax3b-3)in olive flounder,but their roles in myogenesis are unknown.In this study,we investigated their cellular localization,transcriptional activity on myod gene regulation,and roles in myogenesis.Different Pax3a and Pax3b isoforms revealed various subcellular localizations,which were related to their corresponding protein structures.Pax3a-1,Pax3a-2,and Pax3b-1 promoted the transcriptional activity of myod to dif-ferent degrees,whereas Pax3b-2 and Pax3b-3 had a slight inhibitory or no effect.The pairwise interaction analysis demonstrated the synergistic effect of Pax3b-1 and Pax3b-3 on myod transcriptional activity.The overexpression of different pax3a and pax3b isoforms differentially altered the spatial expression patterns of myod and differentially regulated the expression levels of their target genes(myod,myf5,and c-met)in zebrafish embryonic myogenesis.In addition,the different flounder myod promoter-driven pax3a/3b isoform expression vectors were successfully introduced into the skeletal muscles of juvenile flounder by electroporation.How-ever,none of them could change the mRNA expression levels of mstn,myf5,myod,myogenin,pax7a,and pax7b in the electroporated muscles.These results suggest that different Pax3a and Pax3b isoforms may precisely and collaboratively regulate embryonic myogenesis,but their roles in juvenile myogenesis are uncertain.

Tempo-spatial distribution of Ulva spp.micro-propagules in the Yellow Sea during and after green tide in 2019

Large-scale green tides occur frequently in summer in the Yellow Sea in recent decade.Micropropagules,providing“seeds”for the seaweeds,play an important role in the formation of green tide.We studied the distribution pattern and genetic composition of the Ulva micro-propagules in the Yellow Sea during and after the green tide in 2019.In April,a great amount of Ulva micro-propagules was detected in the Subei Shoal,with the average density of 908 inds./L,being similar to that of previous studies.U.prolifera was found out at a low percentage(4%),and 25%of them were positive when tested by the specific marker for the floating ecotype.The percentage of U.prolifera was obviously lower than that in the same season from 2009 to 2016.Therefore,the quantity of U.prolifera micro-propagules sharply decreased.Significant variation in composition of the micro-propagules in Subei radial sand ridges was revealed in the background of the alternation of macroalgal tides in the Yellow Sea in the latest years.During the green tide in June and July,Ulva micro-propagules were detected from some nearshore sites where the floating seaweeds distributed,and U.prolifera was the dominate species.In September,when the green tide ended,no Ulva micro-propagule was detected from the open sea area of the Yellow Sea.It is indicated that the green algae micro-propagules were unlikely to exist in the open water of the Yellow Sea for a long time according to the large-scale surveys.The mechanism of preserving micro-propagules in Subei radial sand ridges,and the destination of U.prolifera micro-propagules in the open sea area of the Yellow Sea after green tide deserves further study.

Near-infrared spectroscopy method for rapid proximate quantitative analysis of nutrient composition in Pacific oyster Crassostrea gigas

Glycogen,amino acids,fatty acids,and other nutrient components affect the flavor and nutritional quality of oysters.Methods based on near-infrared reflectance spectroscopy(NIRS)were developed to rapidly and proximately determine the nutrient content of the Pacific oyster Crassostreagigas.Samples of C.gigas from 19 costal sites were freeze-dried,ground,and scanned for spectral data collection using a Fourier transform NIR spectrometer(Thermo Fisher Scientific).NIRS models of glycogen and other nutrients were established using partial least squares,multiplication scattering correction first-order derivation,and Norris smoothing.The R_(C) values of the glycogen,fatty acids,amino acids,and taurine NIRS models were 0.9678,0.9312,0.9132,and 0.8928,respectively,and the residual prediction deviation(RPD)values of these components were 3.15,2.16,3.11,and 1.59,respectively,indicating a high correlation between the predicted and observed values,and that the models can be used in practice.The models were used to evaluate the nutrient compositions of 1278 oyster samples.Glycogen content was found to be positively correlated with fatty acids and negatively correlated with amino acids.The glycogen,amino acid,and taurine levels of C.gigas cultured in the subtidal and intertidal zones were also significantly different.This study suggests that C.gigas NIRS models can be a cost-effective alternative to traditional methods for the rapid and proximate analysis of various slaughter traits and may also contribute to future genetic and breeding-related studies in Pacific oysters.

Genome Editing in the Olive Flounder(Paralichthys olivaceus)Using CRISPR/Cas9 and a Simple Microinjection System

The whole-genome sequence of the olive flounder(Paralichthys olivaceus)provides a basis for gene functional analyses,which is important for the aquaculture industry.Understanding gene function will help us to select better economic traits such as fast growth and better culture conditions,which further will increase the aquaculture output.Gene knockout is an important reverse genetics approach for in vivo studies of gene function.In this study,the CRISPR/Cas9 genome editing method with a microinjection system using a simple braked needle was employed in olive flounder.After injection in embryos,green fluorescent protein expression was detected in 40%of larvae.The proportion of normal-hatched larvae was approximately 50%.Different mutations,including short indels and fragment deletions,were found in our test genes gsdf and myomaker.Additionally,we detected more than one mutation in a single larva.In summary,our microinjection technique and CRISPR/Cas9 can be applied to study gene functions in olive flounder.

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.

Comparative chloroplast genomes of Ulva prolifera and U.linza(Ulvophyceae)provide genetic resources for the development of interspecific markers

The green seaweeds Ulva linza and U.prolifera are closely related species.They usually co-occur widely and have important ecological significance as primary producers thriving in the intertidal zone.In the Yellow Sea,a genetically unique floating ecotype of U.prolifera even bloomed to cause serious green tides.However,there is still a lack of appropriate molecular markers to distinguish these two species,partially due to limited evaluations on the intraspecific variations in U.prolifera among dif ferent ecotypes.Since organelle genomes could provide rich genetic resources for phylogenetic analysis and development of genetic markers,in this study,the chloroplast genome from one attached population of U.prolifera was completely sequenced,and comparative genomic analyses were performed with other existing chloroplast genomes from U.linza and the floating ecotype of U.prolifera.The results showed that in spite of the high level of collinearity among three genomes,there were plenty of genetic variations especially within the non-coding regions,including introns and gene spacer regions.A strategy was proposed that only those signals of variation,which were identical between two ecotypes of U.prolifera but divergent between U.linza and U.prolifera,were selected to develop the interspecific markers for U.linza and U.prolifera.Two candidate markers,psa B and pet B,were shown to be able to distinguish these two closely related species and were applicable to more attached populations of U.prolifera from a wide range of geographical sources.In addition to the interspecific marker,this study would also provide resources for the development of intraspecific markers for U.prolifera.These markers might contribute to the surveys for Ulva species composition and green tide monitoring especially in the Yellow Sea region.

Immunostimulatory eff ect of quaternary degree and acetyl group of quaternized chitosan on macrophages RAW 264.7

Hydroxypropyltrimethyl ammonium chloride chitosan(HACC)and hydroxypropyltrimethyl ammonium chloride fully deacetylated chitosan(De-HACC)were synthesized with various degrees of substitution by altering the ratio of chitosan to glycidyl trimethyl-ammonium chloride(GTMAC).The effects of the quaternary ammonium degree and the acetyl group of these polymers on immunostimulatory activities were detected in RAW 264.7 cells.The expression levels of nitrogen oxide(NO),interleukin-6(IL-6)and tumor necrosis factor(TNF-α)were compared.Results show that the removal of acetyl groups in chitosan obviously improved the degree of substitution of quaternary ammonium salts.In addition,HACC and De-HACC were capable of promoting immunological activity in a substitution-dependent manner;HACC was positively correlated,and De-HACC was negatively correlated.Among tested ratios,HACC-30%and De-HACC-54%performed better than the others,and De-HACC-54%performed the best.Generally,quaternized chitosan possesses immunostimulatory activity,which is related to the degree of quaternization and the acetyl group.

Low genetic diversity in the endangered marine alga Silvetia siliquosa(Ochrophyta:Fucaceae)and the implication to conservation

Although signifi cant research eff orts have been targeted toward conservation and management of endangered terrestrial fl ora and fauna,attempts have been limited to conserve threatened seaweeds.Silvetia siliquosa is an ecologically and commercially vital brown alga that is uniquely distributed in the Yellow-Bohai Sea and along the southwest coast of Korea.A massive decline in its distribution range and biomass from the mid-1990s onward indicates that this species has become endangered.In the present study,we used nuclear internal transcribed spacer and concatenated mitochondrial cytochrome oxidase I subunit+intergenic spacer to estimate the genetic diversity,population connectivity,and degree of genetic diff erentiation of S.siliquosa in China and Korea.The molecular results exhibited strikingly low levels of haplotype/ribotype and nucleotide diversity in S.siliquosa populations,with only three mitochondrial haplotypes and nuclear ribotypes detected in 136 and 143 specimens,respectively.The analysis of molecular variance revealed 85%-95%of genetic variance among populations.Population diff erentiation coeffi cient(F_(ST))and gene fl ow(N_(m))suggested that two populations(JIN and GWA)along the southern coast of Korea are highly divergent from the others,with weak genetic exchange.No signifi cant genetic diff erentiation was observed among populations either in China or along the geographically proximate west coast of Korea.Thus,four independent management units were designated for sustainable management:the LII and RUS populations in China,the YEO and CHA populations along the west coast of Korea,and each of the GWA and JIN populations along the south coast of Korea.We suggest that artifi cial cultivation and transplantation of S.siliquosa are the eff ective approaches for restoration and conservation.

Isolation and characterization of three pairs of verrucosidin epimers from the marine sediment‑derived fungus Penicillium cyclopium and confguration revision of penicyrone A and related analogues

Verrucosidins,a methylatedα-pyrone class of polyketides rarely reported upon,have been implicated in one or more neurological diseases.Despite the signifcance of verrucosidins as neurotoxins,the absolute confgurations of most of the derivatives have not been accurately characterized yet.In this study,three pairs of C-9 epimeric verrucosidin derivatives,including the known compounds penicyrones A and B(1a/1b)and 9-O-methylpenicyrones A and B(2a/2b),the new compounds 9-O-ethylpenicyrones A and B(3a/3b),together with the related known derivative verrucosidin(4),were isolated and identifed from the culture extract of Penicillium cyclopium SD-413,which was obtained from the marine sediment collected from the East China sea.Their structures were established based on an in-depth analysis of nuclear magnetic resonances(NMR)and mass spectroscopic data.Determination of the absolute confgurations of these compounds was accomplished by Mosher’s method and time-dependent density functional theory(TDDFT)calculations of electronic circular dichroism(ECD)and optical rotation(OR).The confgurational assignment of penicyrone A demonstrated that the previously reported C-6 absolute confguration of verrucosidin derivatives needs to be revised from(6S)to(6R).The 9R/9S epimers of compounds 1–3 were found to exhibit growth inhibition against some pathogenic bacteria,indicating that they have potential as lead compounds for the creation of antimicrobial agents.

PSI-driven cyclic electron fl ow partially alleviates the peroxidation of red alga Gelidium amansii(Gelidiaceae)caused by temporary high temperature

PSI-driven cyclic electron fl ow(CEF-I)helps higher plants avoid severe heat damage.Gelidium amansii,a red seaweed used in the production of agar,inhabits subtidal rocks but can be found in the intertidal zone.The biological role of CEF-I is still unclear in this organism.Wild G.amansii was exposed to 30℃heat stress for 12 h with continuous lighting.The results showed that treatment at 30℃gradually decreased maximal PSII photochemical effi ciency(F_(v)/F_(m)),linear electron transfer rate,and activity of photosynthetic reaction center.Both the maximal photochemical effi ciency under light(F_(v)'/F_(m)')and maximum quantum yield of light-adapted PSII(Φ_(PSII))were maintained at a relatively stable level during the initial 6 h and then signifi cantly decreased at 12 h.The up-regulated CEF-I helps to enhance proton gradient transfer across thylakoid membrane to protect oxygen-evolving complex against heat damage.Following the addition of a CEF-I inhibitor to plants,the F_(v)/F m greatly decreased,suggesting that the CEF-I alleviates degree of photoinhibition caused by strong light.The results of measurement of antioxidant enzymes,including superoxide dismutase(SOD),ascorbate peroxidase(APX)and catalase(CAT),and the contents of H_(2)O_(2)and malonaldehyde(MDA)provided additional evidence that CEF-I plays a protective role to a certain extent for G.amansii to manage stress at 30℃.Therefore,it can be concluded that CEF-I enables G.amansii to survive in intertidal zones by protecting it from the heat damage caused by high temperature stress.

Variations in nano-and pico-eukaryotic phytoplankton assemblages in the Qinhuangdao green-tide area

Qinhuangdao coastal waters have been frequently hitting by nano-and pico-eukaryotic phytoplankton(NPEP)blooms and green tides(macroalgal blooms)in the recent decade.However,understanding about the impacts of environmental factors and the green tides on the NPEP assemblages in this area is limited.In this study,the composition of NPEP assemblages and their variations were analyzed via amplicon sequence variants(ASVs)assay based on amplicon high-throughput sequencing data with the 18S V4 region as a targeted gene in the Qinhuangdao green-tide area during the green tide.Consequently,average NPEP effective sequences and ASVs of 178000 and 200 were obtained from each sample,respectively.Although there were 25 classes,110 genera,and 97 species of NPEP were identified and annotated,the proportions of annotated ASVs at genus and species levels were only 44.7%and 17.8%,respectively.The NPEP communities had a seasonal succession from diatom-dominated to dinoflagellate-dominated.During the three investigations,Skeletonema,Karlodinium,and Gonyaulax were the most dominant genera in May,August,and September,respectively.Species diversity and the abundance of NPEP communities could be increased by a high content of dissolved organic nitrogen(DON)and dissolved organic phosphorus(DOP)but inhibited by low dissolved inorganic phosphorus content.The outbreak of green tides could alter the composition and content of nutrients and accelerate the succession of the NPEP communities from diatom-dominated to dinoflagellate-dominated under the background of a seasonal increase in seawater temperature.These results preliminarily revealed the impacts of the recurrent occurrences of green tides on the NPEP assemblages in the Qinhuangdao green-tide area exhibiting high DON content and dissolved inorganic nitrogen/phosphorus ratio.