Photoperiod Mediates the Effects of Temperature and Light Intensity on the Proliferation of Ulva prolifera

In order to study the complex effects of photoperiod,temperature,and light intensity on the spore maturation and release number of Ulva prolifera,we cultured thalli segment(2–3 mm)under three different photoperiods(L:D=12:12,14:10 and 10:14),temperature(15℃(LT),25℃(MT)and 30℃(HT))and light intensity(100,200 and 400μmol m^(−2)s^(−1),noted as LL,ML and HL,respectively)conditions.Then the maturation time,spore release number and chlorophyll fluorescence were analyzed.The results suggested that:1)The spore maturation time was accelerated by higher temperature or higher light intensity from 62 h to 36 h,and changes in day length accelerated the spore maturation to a certain extent as compared with 12:12 light/dark cycle;2)Higher light intensity significantly decreased the chlorophyll fluorescence(Fv′/Fm′,NPQ,rETRmax andα)of the mature reproductive segment under 30℃with 12:12 light/dark cycle.But when in the other photoperiods(10:14 and 14:10 conditions),the inhibitory effects of high light intensity were alleviated significantly;3)The optimum condition for the spore maturation and release was 12:12 light/dark cycle,25℃,400μmol m^(−2)s^(−1),with both shorter and longer photoperiod reducing the spore release number;4)Higher light intensity significantly increased the spore release number under 25℃,but these effects were alleviated by 30℃treatment.This study is the first attempt to elucidate the coincidence effects of photoperiod,temperature and light intensity on the reproduction of Ulva,which would help to reveal the mechanism of the rapid proliferation of green tide.

Study of screening,transport pathway,and vasodilation mechanisms on angiotensin-Ⅰconverting enzyme inhibitory peptide from Ulva prolifera proteins

In this study,Ulva prolifera protein was used for preparing angiotensin-I converting enzyme(ACE)-inhibitory peptide via virtual gastrointestinal digestion and in silico screening.Some parameters of the obtained peptide,such as inhibition kinetics,docking mechanism,stability,transport pathway,were explored by Lineweaver-Burk plots,molecular docking,in vitro stimulate gastrointestinal(GI)digestion and Caco-2 cells monolayer model,respectively.Then,a novel anti-ACE peptide LDF(IC_(50),(1.66±0.34)μmol/L)was screened and synthesized by chemical synthesis.It was a no-competitive inhibitor and its anti-ACE inhibitory effect mainly attributable to four Conventional Hydrogen Bonds and Zn701 interactions.It could keep activity during simulated GI digestion in vitro and was transported by peptide transporter PepT1 and passive-mediated mode.Besides,it could activate Endothelial nitric oxide synthase(eNOS)activity to promote the production of NO and reduce Endothelin-1(ET-1)secretion induced by AngiotensinⅡ(AngⅡ)in Human Umbilical Vein Endothelial Cells(HUVECs).Meanwhile,it could promote mice splenocytes proliferation in a concentration-dependent manner.Our study indicated that this peptide was a potential ingredient functioning on vasodilation and enhancing immunity.

Effects of Ulva prolifera dissipation on the offshore environment based on remote sensing images and field monitoring data

Outbreaks of Ulva prolifera have continued in the South Yellow Sea of China(SYS)since 2007,becoming a serious marine ecological disaster.Large amounts of U.prolifera drift to the coast of the Shandong Peninsula to dissipate under the action of southeast monsoons and ocean surface currents.This causes serious harm to the ecological environment and economic activities of coastal cities.To investigate the impact of U.prolifera dissipation,this study extracted the spatiotemporal distribution of U.prolifera in the SYS from 2012 to 2020 based on the Google Earth Engine.The outbreak cycle of U.prolifera was determined by fitting analysis of outbreak time and coverage area through MATLAB.This study also looked at the effect of U.prolifera dissipation on water quality through field monitoring data.The results showed that the growth curve of the U.prolifera has a significant Gaussian distribution.The U.prolifera dissipates in Haiyang,China,in July and August every year and affects the offshore environment.Water quality parameters of seawater at different depths had significant differences after the U.prolifera dissipation.Changes in pH,chemical oxygen demand,nitrite nitrogen,nitrate nitrogen,ammonia nitrogen,chlorophyll a,total phosphorus,and suspended solids were more significant in surface seawater than in deeper water.Changes in the concentrations of dissolved oxygen and total nitrogen were more significant in the deep seawater(1.63 and 1.1 times higher than those in the surface seawater,respectively).The dissipation of U.prolifera releases a large amount of carbon and nitrogen into the seawater,which provides rich nutrients for phytoplankton and may cause secondary disasters such as red tide.These findings are useful for further understanding the rules of U.prolifera dissipation,as well as preventing and controlling green tide disasters.

Characterization of SARS-COV-2 main protease inhibitory peptides from Ulva prolifera proteins

The main protease(M^(pro))is essential for the replication of SARS-COV-2 and therefore represents a promising anti-viral target.In this study,we screened M^(pro)inhibitory peptides from Ulva prolifera protein on in-silico proteolysis.Cytotoxicity analysis using the online toxic prediction tool ToxinPred revealed that all the peptides were non-cytotoxic.The hexapeptide(SSGFID)exhibited high M^(pro)inhibitory activity in molecular docking and its IC_(50)value was 139.40±0.82μmol/L in vitro according to fluorescence resonance energy transfer assay(FRET).Quantitative real-time(qRT-)PCR results show that SSGFID could stimulate the expression of mitosis-related factors,including nuclear factor-κB,cyclin D1,and cyclin-dependent kinase 4,to promote the proliferation of mice splenocytes.Stability study revealed that SSGFID showed resistance against pepsin and trypsin but lost D(Asp)after pretreatment at121℃ for 15 min.Besides,SSGFID was mainly transported through the Caco-2 cell monolayer by the peptide transporter PepT1 and passive-mediated transport during the transport study.Unfortunately,the peptide was also degraded by Caco-2 intracellular enzymes,and the transfer rate of intact peptide was4.2%.Furthermore,Lineweaver–Burk plots demonstrated that SSGFID possessed a mixed inhibitory characteristic with M^(pro).Our study indicated the potential of Ulva prolifera as antiviral and immuneenhancing functional food ingredients and nutraceuticals.

Eutrophication of Jiangsu Coastal Water and Its Role in the Formation of Green Tide

Since 2007,the large-scale green tide caused by Ulva prolifera(U.prolifera)have occurred as a recurrent phenomenon in the southern Yellow Sea of China.Field surveys and satellite remote sensing showed that the small scattered patches of green tide algae were first observed along the Porphyra agriculture area of the Subei Shoal in late April.In this study,we attempted to identify the role of eutrophication in the origin of the green tide in the Subei Shoal and its adjacent area.Subei Shoal and its adjacent area are characterized by rich nutrients,especially NO_(3)^(-)-N,NH_(4)^(+)-N,PO_(4)^(3-)-P,and other bioavailable components(such as urea-N and amino acids).In the spring of 2017,the average concentrations of NO_(3)^(-)-N were 19.01±11.01μmolL^(-1),accounting for 86.68%of the dis-solved inorganic nitrogen(DIN).In addition,the average concentration of NH4^(+)-N was 2.51±1.60μmolL^(-1).PO_(4)^(3-)-P had an average concentration of 0.14±0.13μmolL-1.The average concentrations of urea-N and total hydrolyzed amino acids(THAA)were 1.73±1.36μmolL^(-1)and 1.33±0.80μmolL^(-1),respectively.Rich nutritive substances play a key role in the rapid production of U.prolifera and make the Jiangsu coastal water an incubator for green tide.

Genome-wide SNP markers provided insights into the reproductive strategy and genetic diversity of the green tide causative species Ulva prolifera in China

Ulva prolifera is the causative species of the annually occurring large-scale green tides in China since 2007.Its specific biological features on reproductivity strategies,as well as intra-species genetic diversity,are still largely unknown,especially at the genome level,despite their importance in understanding the formation and outbreak of massive green tides.In the present study,the restriction site-associated DNA genotyping approach(2b-RAD)was adopted to identify the genome-wide single-nucleotide polymorphisms(SNPs)of 54 individual thalli including samples collected from Subei Shoal in 2019 and Qingdao coast from 2019 to 2021.SNPs genotype results revealed that most of the thalli in 2019 and 2020 were haploid gametophytes,while only half of the thalli were gametophytes in 2021,indicating flexibility in the reproductive strategies for the formation of the green tides among different years and the dominance of asexual and vegetative reproductive mode for the floating period.Besides,population analysis was conducted,and it revealed a very low genetic diversity among samples from Subei Shoal and the Qingdao coast in the same year and a higher divergence among samples in different years.The results showed the efficiency of 2b-RAD in the exploration of SNPs in U.prolifera and provided the first genome-wide scale evidence for the origin of the large-scale green tides on the Qingdao coast.This study improved our understanding of the reproductive strategy and genetic diversity of the green tide causative species and will help further reveal the biological causes of the green tide in China.

WWOX induces apoptosis and inhibits proliferation of human hepatoma cell line SMMC-7721

AIM: To investigate the effects of the WWOX gene on the human hepatic carcinoma cell line SMMC-7721. METHODS: Full-length WWOX cDNA was amplified from normal human liver tissues. Full-length cDNA was subcloned into pEGFP-N1, a eukaryotic expression vector. After introduction of the WWOX gene into cancer cells using liposomes, the WWOX protein level in the cells was detected through Western blotting. Cell growth rates were assessed by methyl thiazolyl tetrazolium (MTT) and colony formation assays. Cell cycle progression and cell apoptosis were measured by flow cytometry. The phosphorylated protein kinase B (AKT) and activated fragments of caspase-9 and caspase-3 were examined by Western blotting analysis. RESULTS: WWOX significantly inhibited cell proliferation, as evaluated by the MTT and colony formation assays. Cells transfected with WWOX showed significantly higher apoptosis ratios when compared with cells transfected with a mock plasmid, and overexpression of WWOX delayed cell cycle progression from G1 to S phase, as measured by flow cytometry. An increase in apoptosis was also indicated by a remarkable activation of caspase-9 and caspase-3 and a dephosphorylation of AKT (Thr308 and Ser473) measured with Western blotting analysis. CONCLUSION: Overexpression of WWOX induces apoptosis and inhibits proliferation of the human hepatic carcinoma cell line SMMC-7721.

Physical-biogeochemical interactions and potential effects on phytoplankton and Ulva prolifera in the coastal waters off Qingdao(Yellow Sea, China)

In recent years, the spectacular massive green tide of Ulva prolifera has become a recurrent phenomenon appearing every summer in the coastal waters off Qingdao(Yellow Sea, China), attracting the attention of scientists and local government. Based on multidisciplinary data collected during summer and winter, this study focuses on the hydrological characteristics and regional biogeochemical processes in coastal waters off Qingdao.The results show that the boundary of the Yellow Sea Cold Water Mass(YSCWM) can reach the Qingdao coastal region in summer and is locally raised to the upper layers to form coastal upwelling beyond tidal mixing and favorable wind. The regional summer upwelling off the Qingdao coast effectively enriches the nutrient concentrations in the upper water column and thus promotes growth of phytoplankton but reduces the dissolved oxygen(DO) concentration and pH value in the bottom. The regional summer upwelling off Qingdao coast may facilitate the growth and regional blooming of the U. prolifera that migrate to this region with the southerly wind.Additionally, the effects of the front on the aggregation of U. prolifera may be significant. In winter, the Yellow Sea Warm Current(YSWC) extends and spreads along the offshore region off the Subei Shoal towards the Qingdao coastal sea. This tongue-shaped warm water meets the cold coastal water off Qingdao, which leads to the formation of a physical front. As a consequence, remarkable fronts of nutrient and chlorophyll a(Chl a) also form between the shoreward warm water and the cold coastal water. This study increases the understanding of the interactions between the regional physical, chemical, and biological processes off the Qingdao coast.

Selenylation Modification of Degraded Polysaccharide from Enteromorpha prolifera and Its Biological Activities

Polysaccharide extracted from Enteromorpha prolifera possessed excellent biological activities,but its molecular weight was greatly high which influenced the activity.Organic Se had higher biological activities and was safer than inorganic Se species.In the present study,Enteromorpha polysaccharide was degraded to low molecular weight by free-radical degradation method of H_2O_2 and ascorbic acid.By single factor and orthogonal experiments,the optimal degradation conditions were reaction time of 2 h,reaction temperature of 50℃,H_2O_2/ascorbic acid(n/n=1:1)concentration of 15 mmol L^(-1),and solid-liquid ratio of 1:50(g mL^(-1)).Then,the degraded polysaccharide was chemically modified to obtain its selenide derivatives by nitric acid-sodium selenite method.The selenium content was 1137.29μg g^(-1),while the content of sulfate radical had no change.IR spectra indicated that the selenite ester group was formed.Degraded polysaccharide selenide was characterized and evaluated for antioxidant,antifungal and antibacterial activities.The results showed that degraded polysaccharide selenide had strong capacity of scavenging DPPH and·OH free radical.It had significant antibacterial properties for Escherichia coli,Bacillus subtilis and Salmonella spp.,and it also had significant antifungal properties for Apple anthrax.The result ascertained degradation and selenylation modification did not change the main structure of polysaccharides.It was possible that free-radical degradation was an effective way for enhancing antioxidant activity to decrease molecular weight of polysaccharides.

The contribution of attached Ulva prolifera on Pyropia aquaculture rafts to green tides in the Yellow Sea

Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007.The primary source of the Yellow Sea green tides is the attached algae on the Pyropia aquaculture rafts in the Subei Shoal.Ulva prolifera and Blidingia(Italic)sp.are the main species observed on Pyropia aquaculture rafts in the Subei Shoal.We found that U.prolifera has strong buoyancy and a rapid growth rate,which may explain why it is the dominant species of green tides that occur in the China's sea area of the Yellow Sea.The growth rate of floating U.prolifera was about 20%–31%d–1,which was much higher than Blidingia(Italic)sp.There were about 1.7×104 t of attached algae on the Pyropia aquaculture rafts in May 2012.We found that 39%of attached algae could float when the tide rose in the Subei Shoal,and U.prolifera accounted for 63%of the floating algae.Our analysis estimated that about 4000 t of attached U.prolifera floated into the surrounding waters of the Subei Shoal during the recycling period of aquaculture rafts.These results suggest that the initial floating biomass of large-scale green tides in the Yellow Sea is determined by the U.prolifera biomass attached to Pyropia aquaculture rafts,further impacting the scale of the green tide。

Purification and Characterization of a Novel Hydrolase That Can Specifically Degrade the Polysaccharide Isolated from Green Seaweed Ulva prolifera

The extracellular polysaccharide hydrolase-producing strain EP-1 was isolated from seawater and identified as Paenibacillus pabuli. Furthermore, a homogeneous extracellular polysaccharide hydrolase from Paenibacillus pabuli EP-1 was purified by combining ion-exchange chromatography and size exclusion chromatography with a purification fold of 90.69 and recovery of 16.23%. Characterization of the purified polysaccharide hydrolase revealed a molecular mass of 38 k Da and optimum activity at 45℃ and pH 6.0. The polysaccharide hydrolase maintained its stability within a wide range of pH(3.0–12.0) and thermal stability when the temperature was below 50℃. The presence of Hg^(2+), Fe^(2+), Mn^(2+), Co^(2+) and SDS notably decreased hydrolase activity, and organic solvents such as formaldehyde, acetone, DMF and acetonitrile completely inhibited hydrolase activity. The purified hydrolase had no activity on agar, carrageenan, gellan gum, sodium alginate, or starch, but effectively hydrolyzed the polysaccharide from Ulva prolifera. The Km and Vmax values of this hydrolase were 43.84 mg m L^(-1) and 4.33 mg m L^(-1) min^(-1), respectively. The sequence analysis with quantitative time-of-flight mass spectrometry indicated that the hydrolase was an endoglucanase.

Adsorption of Reactive Dyes on Activated Carbon Developed from <i>Enteromorpha prolifera</i>

Activated carbon was prepared from Enteromorpha prolifera by zinc chloride activation. The adsorption behaviors of three reactive dyes (Reactive Red 23, Reactive Blue 171 and Reactive Blue 4) onto this biomass activated carbon were investigated in batch systems. The experimental findings showed that the removal efficiencies of three dyes onto activated carbon were maximum at the initial solution pH of 4.5 - 6.0. Thermodynamic studies suggested that adsorption reaction was an endothermic and spontaneous process. Adsorption isotherm of the three dyes obeyed Freundlich isotherm modal. Dye adsorption capacities of activated carbon were 59.88, 71.94 and 131.93 mg·g?1 for RR23, RB171 and RB4 at 27?C, respectively. Second-order kinetic models fitted better to the equilibrium data of three dyes. The adsorption process on activated carbon was mainly controlled by intraparticle diffusion mechanism.

Effect of temperature and irradiance on the growth and reproduction of Enteromorpha prolifera J.Ag.(Chlorophycophyta,Chlorophyceae)

开花的 Enteromorpha prolifera 的生长和复制上的温度和发光的效果沿着在夏天 2008 的 Qingdao 海岸近海，被学习。它被看那 E。在 25 ° C /40 μmol m −2 s −1 。在这个条件下面，有二的配偶子鞭打在 5 形成了并且释放天。在发展的开始， unicell 配偶子与异种极性把房间划分了成二，然后顶端的房间开发了初发的房间进 thalli，而基础房间发展成假根的初发的房间。在 8 天的文化，单音的原浆配偶子在长度发展成 240 μm 的少年细菌石楠。Unreleased 配偶子能在水藻身体以内直接发展。E。prolifera 也能通过除了显微镜的观察揭示的单性生殖的侧面的分叉或碎裂复制。在 E 的年老的织物上。prolifera 尽管降级的颜料部分留在褪色的海藻的细丝，众多的植物的房间能仍然在海藻的纸巾活跃地划分。

Spatiotemporal distribution and influencing factors of Ulva prolifera and Sargassum and their coexistence in the South Yellow Sea,China

Marine ecological disasters occurred frequently in recent years and raised widespread concerns about the ecological health of the ocean.We analyzed the spatiotemporal distributions of Ulva prolifera and Sargassum from April to July each year between 2016 and 2020 in the South Yellow Sea using multisource(GF-1 and HJ-1A/1B)remote sensing images,combined with the MODIS sea surface temperature(SST)data,photosynthetically active radiation(PAR)data,and Quick SCAT sea surface wind(SSW)data,to explore the potential influencing factors.The results show that(1)U.prolifera and Sargassum appeared mainly from May to July and April to June,respectively;(2)U.prolifera showed an impact in larger spatial scope than that of Sargassum.U.prolifera originated in the shoal area of northern Jiangsu and finally disappeared in the sea near Haiyang-Rongcheng area.The spatial scope of the impact of Sargassum tended to expand.Sargassum was first detected in the ocean northeast of the Changjiang(Yangtze)River estuary and disappeared near 35°N;and(3)correlation analysis showed that the SST influenced the growth rate of U.prolifera and Sargassum.PAR had varied eff ects on U.prolifera and Sargassum at different times.A moderate light conditions could accelerate the growth and reproduction of U.prolifera and Sargassum.High irradiance levels of ultraviolet radiation may cause photoinhibition and damage on U.prolifera and Sargassum.The southeast monsoon and surface currents promoted the drift of U.prolifera and Sargassum from the southeast to the northwest and north.Therefore,the spatial and temporal similarities and differences between U.prolifera and Sargassum were influenced by a combination of factors during their growth processes.

Combined effects of light intensity and NH_4^+-enrichment on growth, pigmentation, and photosynthetic performance of Ulva prolifera(Chlorophyta)

The aim of this study was to investigate the effects of light intensity and enhanced nitrogen supply on the growth and photosynthesis of the green-tide macroalga, Ulva prolifera. Thalli of U. prolifera were grown in natural or NH 4 +-enriched seawater under two different light intensities for 7 days, and then the growth rate, pigmentation, and photosynthetic performance of the thalli were evaluated. The results show that the relative growth rate(RGR) was markedly higher under the high light level than under the low light level. Enrichment with NH 4 + enhanced the RGR under high light intensity, but did not affect RGR under low light intensity. In low light conditions, NH 4 +-enrichment resulted in a marked decrease in the maximal photosynthetic rate( P m) and the maximum carbon fixation rate( V max), but it did not affect the half saturation constant for carbon( K 0.5) or the ratio of V max to K 0.5, which reflects the carbon acquisition efficiency. In high light conditions, P m, K 0.5, and the dark respiration rate( R d) increased under NH 4 + enrichment, but V max and the V max / K 0.5 ratio decreased. Regardless of the light intensity, NH 4 +-enrichment did not affect the apparent photosynthetic efficiency( α), which refl ects the ability of the alga to use light energy at low light levels. Under both low and high light intensities, the chlorophyll a(Chl a), chlorophyll b(Chl b), and carotenoids(Car) contents in thalli were higher in NH 4 +-enriched than in natural seawater, except that there was a decrease in the Chl b content of thalli in NH 4 +-enriched seawater under low light intensity. Therefore, NH 4 + enrichment improved the growth and photosynthetic performance of U. prolifera under high light intensity, but not under low light intensity. We discuss the possible mechanisms underlying these physiological responses.

盐度对浒苔(Ulva prolifera)微观繁殖体萌发生长及藻体繁殖的影响

黄海绿潮起源于苏北浅滩,每年夏天漂移到青岛沿岸泛滥成灾,对生态环境造成严重破坏。苏北浅滩受沿岸径流输入影响,盐度变化范围大,青岛海域盐度较稳定,稍高于苏北浅滩。盐度对浒苔微观繁殖体萌发、藻体生长及繁殖过程具有重要作用,通过室内连续受控实验,系统研究了固定盐度(5、10、15、20、25、30、33、35)和变化盐度(盐度逐渐降低)对浒苔微观繁殖体固着、萌发、藻体生长和繁殖不同阶段的影响,主要结论如下:固着阶段,盐度5不利于浒苔微观繁殖体的固着,盐度10~35对微观繁殖体固着的影响不显著,相同盐度下,孢子的固着量显著高于配子。萌发阶段,不同盐度(5~35)及不同盐度变化形式对微观繁殖体(孢子和配子)的萌发没有显著影响,孢子的萌发速度快于配子,最终均能完全萌发。生长阶段,低盐(5~15)不利于浒苔幼苗的生长。繁殖阶段,当盐度≤10时,浒苔不进行生殖活动;盐度15~35范围内,浒苔可以产生微观繁殖体,完成一个完整的生活史;在绿潮形成过程中,孢子的生殖策略为K对策,配子的生殖策略为R对策。上述结论表明,在苏北浅滩和青岛海域,盐度不是限制浒苔发生发展及繁殖过程的关键环境因子,明确了盐度在绿潮发生过程的作用,为揭示绿潮暴发机制提供科学依据。

Effects of nitrogen specification and culture method on growth of Enteromorpha prolifera

Eutrophication, which is the enrichment of a water mass with inorganic and organic nutrients that support plant growth, is a key factor in stimulating phytoplankton growth. In this study, we determined the effects of various nitrogen sources, different nitrogen concentrations in the culture medium, and two culture methods on the growth of the green alga, Enteromorpha prolifera. The relationship between the specific growth rate of E. prolifera and NO3--N concentration was consistent with that estimated using the Monod equation (R2 = 0.9713, P < 0.01). In the NO3--N medium, the maximum specific growth rate was calculated to be 0.1634/d and the semi-saturation constant was calculated to be 16.86 μmol/L. Our results show that E. prolifera can effectively utilize NH4+-N, NO3--N, and NO2--N and urea-N in the range of 5 to 50 μmol/L. NH4+-N was preferentially assimilated by E. prolifera, and urea-N was favorable for long-term growth.

High efficiency of protoplast preparation for artificially cultured Ulva prolifera(Ulvophyceae,Chlorophyta)

Protoplast isolation was relevant for gene manipulation in U lva, and universal protocols have been proposed based on evaluation for various wildly collected species. However, only clonal laboratory cultures were practical for genetic transformation, and whether applicability of such universal protocol existed for these artificial cultures has never been investigated. In this research, samples in different physiological states or developmental stages were tested in U. prolifera. The results proved that the protoplast yields were strongly dependent on the characteristics of samples. Neither F_v/F_m value nor chlorophyll content exhibited an ideal correlation with the protoplast yields. Alternatively, specific growth rate, coupled with developmental stage, could serve as an ef fective combined index to determine the right time for protoplast isolation. According to this instruction, here we reported the highest yields of protoplast((31.5±1.9)×10~6 cells/g f. wt.) in U. prolifera, following comparison between protocols, and further optimizations on enzyme content, incubation period, starting biomass and pretreatment. This specified protocol for artificially cultured clonal samples could meet the need for protoplast-mediated genetic transformation in U. prolifera.

Isolation, Expression and Characterization of rbc L Gene from Ulva prolifera J. Agardh(Ulvophyceae, Chlorophyta)

Ulva prolifera is a typical green alga in subtidal areas and can grow tremendously fast. A highly efficient Rubisco enzyme which is encoded by Up Rbc L gene may contribute to the rapid growth. In this study, the full-length Up Rbc L open reading frame(ORF) was identified, which encoded a protein of 474 amino acids. Phylogenetic analysis of Up Rbc L sequences revealed that Chlorophyta had a closer genetic relationship with higher plants than with Rhodophyta and Phaeophyta. The two distinct residues(aa11 and aa91) were presumed to be unique for Rubisco catalytic activity. The predicted three-dimensional structure showed that one α/β-barrel existed in the C-terminal region, and the sites for Mg^(2+)coordination and CO_2 fixation were also located in this region. Gene expression profile indicated that Up Rbc L was expressed at a higher level under light exposure than in darkness. When the culture temperature reached 35℃, the expression level of Up Rbc L was 2.5-fold lower than at 15℃, and the carboxylase activity exhibited 13.8-fold decrease. Up Rbc L was heterologously expressed in E. coli and was purified by Ni^(2+) affinity chromatography. The physiological and biochemical characterization of recombinant Rubisco will be explored in the future.

Comparison of Nutritional Components in the Muscle of Juvenile Siganus guttatus Fed with Enteromorpha prolifera and Artificial Feed

[ Objective] This experiment was conducted to analyze and compare the nutritional components in the muscle of juvenile Siganus guttatus fed with Enteromorpha prolifera and artificial feed. [ Method] A total of 180 healthy S. guttatus juveniles with similar body size were assigned into two groups： one fed with E. prolifera, and the other fed with artificial feed, respectively. There were three replicates in each group, and 30 fish in each replicate. And the experiment lasted for 90 d. [ Result] The results showed that the weight gain rate, specific growth rate and relative growth rate of E. prolifera-fed group were significantly lower than those of artificial feed-fed group （P 〈0.05） ; the contents of crude protein and crude ash of E. prolifera-fed group were significantly higher than those of artificial feed-fed group （P 〈 0.05 ）. However, the content of crude fat of E. prolifera-fed group was significantly lower than that of artificial feed-fed group （P 〈 0.05 ）. The moisture content had no significant difference between the two groups （P 〉 0.05 ）. The amino acid composition was similar between the two groups. Seventeen amino acids were found in both groups, and the essential amino acid index （EAAI） was 76.71 in E. prolifera-fed group and 70.05 in artificial feed-fed group, both of which met the criteria set by the Food and Agriculture Organization of the United Nations （FAO）/World Health Organization （WHO）. The content of eicosapentaenoic acid （EPA） ＋ docosahexaenoic acid （DHA） and the content of to-3 polyunsaturated fatty acids （ to-3 PUFAs） of E. prolifera-fed group were significantly higher than those of artificial feed-fed group （ P 〈 0.05 ）. [ Conclusion ] In conclusion, the juvenile S. guttatus in both groups contains a variety of nutritional components. S. guttatus fed with E. prolifera has higher levels of essential amino acids, more balanced composition of polyunsaturated fatty acids, higher nutritive val- ue and better taste than that fed with artificial feed.