Melanosomes are specialized membrane-bound organelles within which melanin is synthesized and stored.The levels of melanin can be effectively reduced by inhibiting melanin synthesis or promoting melanosome degradation...Melanosomes are specialized membrane-bound organelles within which melanin is synthesized and stored.The levels of melanin can be effectively reduced by inhibiting melanin synthesis or promoting melanosome degradation via autophagy.Ceramide,a central molecule in sphingolipid metabolism,has been widely implicated in the regulation of autophagy.Few researchers have addressed the potential effects of ceramide analogs on suppressing melanin synthesis.However,whether ceramide can induce melanosome autophagy and the potential autophagy-dependent mechanism underlying this phenomenon remain unknown.Here,an active compound from the marine microalgae Emiliania huxleyi extract was firstly isolated and identified as a long-chain C22-ceramide(C22-Cer).In vitro results of mouse B16 melanoma cell experiments showed that treatment with 2-5µmol/L C22-Cer significantly suppressed the increase ofα-MSH-induced melanin levels and tyrosinase activity without cytotoxicity.C22-Cer induced typical hallmarks of autophagy such as accumulation of autophagosomes,enhanced autophagic flux and microtubule-associated protein light chain 3,LC3-II expression,and p62 degradation through activating c-Jun N-terminal kinase(JNK)directly.Furthermore,C22-Cer activated JNK-Bcl-2 signaling,dissociated the Beclin1/Bcl-2 complex,and induced melanosome autophagy without affecting the expression of MITF.Besides,the Ca2+influx induced by treatment with C22-Cer further increased the substantial accumulation of autophagosomes.Together,we found a novel marine-derived compound,C22-Cer,targeting JNK pathway and Ca2+signaling to induce melanosome autophagy and suppress melanin accumulation in B16 cells.This study implicates that C22-Cer might be a potential therapeutic mediator against skin pigmentation in mammals.展开更多
The authors have investigated the biochemical events by which marine algal virus infection induces cell cycle arrest. The key G 2 /M-phase regulatory proteins are analyzed by immunobloting in unicel-lular Emiliania hu...The authors have investigated the biochemical events by which marine algal virus infection induces cell cycle arrest. The key G 2 /M-phase regulatory proteins are analyzed by immunobloting in unicel-lular Emiliania huxleyi,suggesting that virus induced cell cycle arrest is related with virus's effect on cyclins and cyclin dependent kinases. E. huxleyi virus(EhV) represses Cdc2/cyclinB complex activity by inhibiting the activity of Cdc2 kinase in a phosphorylation-related manner,blocking host cells G 2 /M checkpoint. Dephosphorylated /inactive Cdc25C combined with up-regulation of Wee1 expression at early infect period appears to be important mechanisms by which EhV represses Cdc2/cyclinB complex activity that is required for entry into M phase. This study has allowed us to confirm that algal virus infection leads to selective activation or inhibition of certain cell-cycle factors,which may play a significant role in establishing a more efficient environment for viral gene expression and DNA replication.展开更多
Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplank...Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplankton.The haploid and diploid life-cycle phases of coccolithophores might have different vertical distribution preferences.Therefore,the two phases respond differently to high solar photosynthetically active radiation(PAR,400-700 nm)and ultraviolet radiation(UVR,280-400 nm).To test this,the haploid and diploid Emiliania huxleyi were exposed to oversaturating irradiance.In the presence of PAR alone,the effective quantum yield was reduced by 10%more due to the higher damage rate of photosystem Ⅱ in haploid cells than in diploid cells.The addition of UVR resulted in further inhibition of the quantum yield for both haploid and diploid cells in the first 25 min,partly because of the increased damage of photosystem Ⅱ.Intriguingly,this UVR-induced inhibition of the haploid cells completely recovered half an hour later.This recovery was confirmed by the comparable maximum quantum yields,maximum relative electron transport rates and yields of the haploid cells treated with PAR and PAR+UVR.Our data indicated that photosynthesis of the haploid phase was more sensitive to high visible light than the diploid phase but resistant to UVR-induced inhibition,reflecting the ecological niches to which this species adapts.展开更多
The authors have isolated and characterized a novel serine palmitoyltransferase (SPT)-like gene in marine Emiliania huxleyi virus (EhV-99B1). The open-reading frame (ORF) of EhV99BI-SPT encoded a protein of 496 ...The authors have isolated and characterized a novel serine palmitoyltransferase (SPT)-like gene in marine Emiliania huxleyi virus (EhV-99B1). The open-reading frame (ORF) of EhV99BI-SPT encoded a protein of 496 amino acids with a calculated molecular mass of 96 kDa and Ip 6.01. The results of sequence analysis showed that there was about 31% 45% identity in amino acid sequence with other organisms. The maximum likelihood phylogenetic tree suggested that the EhV99B1-SPT gene possibly horizontally transferred from the eukaryote. Hydrophobic profiles of deduced amino acid sequences suggested a hydrophobic, globular and membrane-associated protein with five transmembrane domains (TMDs) motifs. Several potential N-linked glycosylation sites were presented in SPT. These results suggested that EhV99BI-SPT was an integral endoplasmic reticulum membrane protein. Despite lower sequence identity, the secondary and three-dimensional structures predicted showed that the “pocket” structure element composed of 2a-helices and 4β- sheets was the catalytic center of this enzyme, with a typical conserved “TFTKSFG” active site in the N-terminal region and was very close to those of prokaryotic organisms. However, the N-terminal domain of EhV99B1-SPT most closely resembled the LCB2 catalysis subunit and the C-terminal domain most closely resembled the LCBI regulatory subunit of other organisms which together formed a spherical molecule. This “chimera” was highly similar to the prokaryotic homologous SPT. For a functional identification, the EhV99B1-LCB2 subunit gene was expressed in Escherichia coli, which resulted in significant accumulation of new sphingolipid in E. coli cells.展开更多
Lipidomics approach by UPLC-Q-Exactive-MS was used for the identification,quantification,comparison,and characterization of sphingolipids in virus infected marine Emiliania huxleyi BOF92 cells.The results show that 16...Lipidomics approach by UPLC-Q-Exactive-MS was used for the identification,quantification,comparison,and characterization of sphingolipids in virus infected marine Emiliania huxleyi BOF92 cells.The results show that 16 significantly changed sphingolipids(including Cer,CerG1,and SPHm)were identified during viral infection.Our data confirmed previously recognized facts that viral infection led to a shift toward virus-specific sphingolipids,which is consistent with the down-regulation of genes involved in the host de novo sphingolipid biosynthesis.Moreover,we revealed the upregulation of virusencoded homologous genes participating in de novo sphingolipids biosynthesis and virus-specific hydroxylated long chain bases(LCBs)as phytoCer,suggesting the competitive inhibition of host sphingolipid synthesis to produce the required building blocks for viral production,replication,and assembly.Additionally,Cer 40꞉1;2,Cer 40꞉2;2 isomer,and CerG139꞉0;2,Cer 39꞉0;2 as novel metabolite markers might indicate the general dysfunctions in E.huxleyi in response to viral infection.Our results show that viral infection led to a profound remodeling of host sphingolipidome,by which viruses depend on the hijacking of host sphingolipid metabolism to support the viral life cycle.展开更多
Inorganic carbon utilization in the non calcifying marine microalgae, Nannochloropsis oculata, Phaeodactylum tricornutum and Porphyridium purpureum was compared with high and low calcifying strains of Emiliania huxley...Inorganic carbon utilization in the non calcifying marine microalgae, Nannochloropsis oculata, Phaeodactylum tricornutum and Porphyridium purpureum was compared with high and low calcifying strains of Emiliania huxleyi grown in artificial seawater medium aerated with either air (0.03% V/V CO 2) or CO 2 free air. For high calcifying strain of E. oculata and P. tricornutem , similar growth patterns were observed in air and CO 2 free air grown cultures. P. purpureum showed a less final cell density in CO 2 free air than in air grown culture. However, low calcifying strain of E. huxleyi was able to grow only in air grown culture, but not in CO 2 free air grown culture. Measurements of alkalinity, pH, concentration of dissolved inorganic carbon (DIC) and free CO 2 showed different patterns of DIC utilization. With N. oculata, P. tricornutum and P. purpureum the pattern of DIC utilization was characterized by an increase of pH and a decrease of DIC but a constant alkalinity in the cultures aerated with air or CO 2 free air, suggesting that bicarbonate utilization was concomitant with an efflux of OH -. Both alkalinity and pH were maintained rather constant in air grown culture of low calcifying strain of E. huxleyi, suggesting that diffusive entry of CO 2 could meet the requirement of DIC for its photosynthesis and growth. High calcifying strain of E.huxleyi , however, showed a pattern of decrease of alkalinity and DIC but an almost constant pH , indicating that bicarbonate was the major form of inorganic carbon utilised by this organism and bicarbonate uptake is unlikely to be accompanied by an efflux of OH -. The final pH values reached by N. oculata, P. tricornutum and P. purpureum in a closed system were 10.75, 10.60 and 9.85 respectively, showing that bicarbonate utilisation is concomitant with an efflux of OH . While the final pH of 8.4 in high calcifying E. huxleyi suggests that bicarbonate utilization was not accompanied by an efflux of OH -.展开更多
Ocean alkalinity enhancement(OAE)via carbonate dissolution has emerged as a promising approach for marine carbon dioxide removal(mCDR).However,the properties of oversaturated seawater in the upper ocean with respect t...Ocean alkalinity enhancement(OAE)via carbonate dissolution has emerged as a promising approach for marine carbon dioxide removal(mCDR).However,the properties of oversaturated seawater in the upper ocean with respect to calcium carbonate(CaCO3)minerals are unfavorable for their dissolution,and mediation strategies are thus required to improve the efficiency of OAE-mCDR.In this study,we conducted laboratory incubation experiments using nearshore surface seawater to examine the dissolution dynamics of natural(Iceland spar)and biogenic(Emiliania huxleyi coccolith)calcite minerals.In the experimental group with added bacteria,total alkalinity(TA)and dissolved inorganic carbon(DIC)concentrations markedly increased over the incubation period,corresponding to a notable decline in pH and dissolved organic carbon concentrations.Moreover,the concentration of dissolved calcium ions increased in the coccolith dissolution experiment.However,in the control group without bacteria,all the parameters were nearly constant or changed only slightly over time in both the Iceland spar and coccolith dissolution experiments.Therefore,microbial mediation clearly enhanced calcite mineral dissolution in oversaturated seawater,which likely occurred in the acidic microenvironments produced by bacterial metabolic activity.Linear regression analyses of the DIC and TA revealed that the relative contribution of CaCO3dissolution to organic matter decomposition was 0.18±0.13 and 0.22±0.01,respectively,in the Iceland spar and coccolith experimental groups.The linear regression slope,defined as the OAE-mCDR efficiency indicating the amount of atmospheric CO2absorbed per unit increase in TA,was 3.53±1.87 and 4.36±0.05 for the two groups.Both values exceed a theoretical value of 0.81 under the incubation seawater conditions,primarily driven by DIC increases from organic matter decomposition in the substrate medium.However,microbe-mineral interactions might also improve OAE performance and capabilities.We propose that microbial mediation plays an important role in promoting carbonate mineral dissolution,even in calcite-oversaturated seawater,and can be incorporated into future mCDR implementation strategies.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42076086 and 32202068)Fujian Province Natural Science Foundation of China(Nos.2019J01696 and 2022J01332)the Fujian Province Young and Middle-Aged Teacher Education Research Project(No.JAT200247).
摘要Melanosomes are specialized membrane-bound organelles within which melanin is synthesized and stored.The levels of melanin can be effectively reduced by inhibiting melanin synthesis or promoting melanosome degradation via autophagy.Ceramide,a central molecule in sphingolipid metabolism,has been widely implicated in the regulation of autophagy.Few researchers have addressed the potential effects of ceramide analogs on suppressing melanin synthesis.However,whether ceramide can induce melanosome autophagy and the potential autophagy-dependent mechanism underlying this phenomenon remain unknown.Here,an active compound from the marine microalgae Emiliania huxleyi extract was firstly isolated and identified as a long-chain C22-ceramide(C22-Cer).In vitro results of mouse B16 melanoma cell experiments showed that treatment with 2-5µmol/L C22-Cer significantly suppressed the increase ofα-MSH-induced melanin levels and tyrosinase activity without cytotoxicity.C22-Cer induced typical hallmarks of autophagy such as accumulation of autophagosomes,enhanced autophagic flux and microtubule-associated protein light chain 3,LC3-II expression,and p62 degradation through activating c-Jun N-terminal kinase(JNK)directly.Furthermore,C22-Cer activated JNK-Bcl-2 signaling,dissociated the Beclin1/Bcl-2 complex,and induced melanosome autophagy without affecting the expression of MITF.Besides,the Ca2+influx induced by treatment with C22-Cer further increased the substantial accumulation of autophagosomes.Together,we found a novel marine-derived compound,C22-Cer,targeting JNK pathway and Ca2+signaling to induce melanosome autophagy and suppress melanin accumulation in B16 cells.This study implicates that C22-Cer might be a potential therapeutic mediator against skin pigmentation in mammals.
基金The National High Technology Research and Development Program of China under contract No. 2008AA09Z408the National Natural Science Foundation of China under contract Nos 40930847, 30940002 and 40876061+1 种基金Fujian Province Natural Science Foundation, China under contract No. 2010J01261the Foundation for Innovative Research Team of Jimei University, China under contract No. 2010A007
摘要The authors have investigated the biochemical events by which marine algal virus infection induces cell cycle arrest. The key G 2 /M-phase regulatory proteins are analyzed by immunobloting in unicel-lular Emiliania huxleyi,suggesting that virus induced cell cycle arrest is related with virus's effect on cyclins and cyclin dependent kinases. E. huxleyi virus(EhV) represses Cdc2/cyclinB complex activity by inhibiting the activity of Cdc2 kinase in a phosphorylation-related manner,blocking host cells G 2 /M checkpoint. Dephosphorylated /inactive Cdc25C combined with up-regulation of Wee1 expression at early infect period appears to be important mechanisms by which EhV represses Cdc2/cyclinB complex activity that is required for entry into M phase. This study has allowed us to confirm that algal virus infection leads to selective activation or inhibition of certain cell-cycle factors,which may play a significant role in establishing a more efficient environment for viral gene expression and DNA replication.
基金funded by the National Key Research and Development Program(2019YFB1503904)National Natural Science Foundation of China(42076206)+1 种基金Guangdong Basic and Applied Basic Research Foundation(2020A1515011073,2016A030313066)Department of Science and Technology of Guangdong Province(2021B1212050025 and STKJ2021125).
摘要Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplankton.The haploid and diploid life-cycle phases of coccolithophores might have different vertical distribution preferences.Therefore,the two phases respond differently to high solar photosynthetically active radiation(PAR,400-700 nm)and ultraviolet radiation(UVR,280-400 nm).To test this,the haploid and diploid Emiliania huxleyi were exposed to oversaturating irradiance.In the presence of PAR alone,the effective quantum yield was reduced by 10%more due to the higher damage rate of photosystem Ⅱ in haploid cells than in diploid cells.The addition of UVR resulted in further inhibition of the quantum yield for both haploid and diploid cells in the first 25 min,partly because of the increased damage of photosystem Ⅱ.Intriguingly,this UVR-induced inhibition of the haploid cells completely recovered half an hour later.This recovery was confirmed by the comparable maximum quantum yields,maximum relative electron transport rates and yields of the haploid cells treated with PAR and PAR+UVR.Our data indicated that photosynthesis of the haploid phase was more sensitive to high visible light than the diploid phase but resistant to UVR-induced inhibition,reflecting the ecological niches to which this species adapts.
基金The National High Technology Research and Development Program of China under contract No. 2008AA09Z408Fujian Province Nature Science Foundation,China under contract No. 2010J01261the Foundation for Innovative Research Team of Jimei University,China under contract No. 2010A007
摘要The authors have isolated and characterized a novel serine palmitoyltransferase (SPT)-like gene in marine Emiliania huxleyi virus (EhV-99B1). The open-reading frame (ORF) of EhV99BI-SPT encoded a protein of 496 amino acids with a calculated molecular mass of 96 kDa and Ip 6.01. The results of sequence analysis showed that there was about 31% 45% identity in amino acid sequence with other organisms. The maximum likelihood phylogenetic tree suggested that the EhV99B1-SPT gene possibly horizontally transferred from the eukaryote. Hydrophobic profiles of deduced amino acid sequences suggested a hydrophobic, globular and membrane-associated protein with five transmembrane domains (TMDs) motifs. Several potential N-linked glycosylation sites were presented in SPT. These results suggested that EhV99BI-SPT was an integral endoplasmic reticulum membrane protein. Despite lower sequence identity, the secondary and three-dimensional structures predicted showed that the “pocket” structure element composed of 2a-helices and 4β- sheets was the catalytic center of this enzyme, with a typical conserved “TFTKSFG” active site in the N-terminal region and was very close to those of prokaryotic organisms. However, the N-terminal domain of EhV99B1-SPT most closely resembled the LCB2 catalysis subunit and the C-terminal domain most closely resembled the LCBI regulatory subunit of other organisms which together formed a spherical molecule. This “chimera” was highly similar to the prokaryotic homologous SPT. For a functional identification, the EhV99B1-LCB2 subunit gene was expressed in Escherichia coli, which resulted in significant accumulation of new sphingolipid in E. coli cells.
基金Supported by the National Natural Science Foundation of China(Nos.42076086,41576166)the Natural Science Foundation of Fujian Province(No.2020J05138)+1 种基金the Education and Research Project for Young and Middle-aged Teachers of Fujian Province(No.JAT190343)the Cultivation Plan for Distinguished Young Scholars in Fujian Universities。
摘要Lipidomics approach by UPLC-Q-Exactive-MS was used for the identification,quantification,comparison,and characterization of sphingolipids in virus infected marine Emiliania huxleyi BOF92 cells.The results show that 16 significantly changed sphingolipids(including Cer,CerG1,and SPHm)were identified during viral infection.Our data confirmed previously recognized facts that viral infection led to a shift toward virus-specific sphingolipids,which is consistent with the down-regulation of genes involved in the host de novo sphingolipid biosynthesis.Moreover,we revealed the upregulation of virusencoded homologous genes participating in de novo sphingolipids biosynthesis and virus-specific hydroxylated long chain bases(LCBs)as phytoCer,suggesting the competitive inhibition of host sphingolipid synthesis to produce the required building blocks for viral production,replication,and assembly.Additionally,Cer 40꞉1;2,Cer 40꞉2;2 isomer,and CerG139꞉0;2,Cer 39꞉0;2 as novel metabolite markers might indicate the general dysfunctions in E.huxleyi in response to viral infection.Our results show that viral infection led to a profound remodeling of host sphingolipidome,by which viruses depend on the hijacking of host sphingolipid metabolism to support the viral life cycle.
摘要Inorganic carbon utilization in the non calcifying marine microalgae, Nannochloropsis oculata, Phaeodactylum tricornutum and Porphyridium purpureum was compared with high and low calcifying strains of Emiliania huxleyi grown in artificial seawater medium aerated with either air (0.03% V/V CO 2) or CO 2 free air. For high calcifying strain of E. oculata and P. tricornutem , similar growth patterns were observed in air and CO 2 free air grown cultures. P. purpureum showed a less final cell density in CO 2 free air than in air grown culture. However, low calcifying strain of E. huxleyi was able to grow only in air grown culture, but not in CO 2 free air grown culture. Measurements of alkalinity, pH, concentration of dissolved inorganic carbon (DIC) and free CO 2 showed different patterns of DIC utilization. With N. oculata, P. tricornutum and P. purpureum the pattern of DIC utilization was characterized by an increase of pH and a decrease of DIC but a constant alkalinity in the cultures aerated with air or CO 2 free air, suggesting that bicarbonate utilization was concomitant with an efflux of OH -. Both alkalinity and pH were maintained rather constant in air grown culture of low calcifying strain of E. huxleyi, suggesting that diffusive entry of CO 2 could meet the requirement of DIC for its photosynthesis and growth. High calcifying strain of E.huxleyi , however, showed a pattern of decrease of alkalinity and DIC but an almost constant pH , indicating that bicarbonate was the major form of inorganic carbon utilised by this organism and bicarbonate uptake is unlikely to be accompanied by an efflux of OH -. The final pH values reached by N. oculata, P. tricornutum and P. purpureum in a closed system were 10.75, 10.60 and 9.85 respectively, showing that bicarbonate utilisation is concomitant with an efflux of OH . While the final pH of 8.4 in high calcifying E. huxleyi suggests that bicarbonate utilization was not accompanied by an efflux of OH -.
基金The National Natural Science Foundation of China under contract No.42421004.
摘要Ocean alkalinity enhancement(OAE)via carbonate dissolution has emerged as a promising approach for marine carbon dioxide removal(mCDR).However,the properties of oversaturated seawater in the upper ocean with respect to calcium carbonate(CaCO3)minerals are unfavorable for their dissolution,and mediation strategies are thus required to improve the efficiency of OAE-mCDR.In this study,we conducted laboratory incubation experiments using nearshore surface seawater to examine the dissolution dynamics of natural(Iceland spar)and biogenic(Emiliania huxleyi coccolith)calcite minerals.In the experimental group with added bacteria,total alkalinity(TA)and dissolved inorganic carbon(DIC)concentrations markedly increased over the incubation period,corresponding to a notable decline in pH and dissolved organic carbon concentrations.Moreover,the concentration of dissolved calcium ions increased in the coccolith dissolution experiment.However,in the control group without bacteria,all the parameters were nearly constant or changed only slightly over time in both the Iceland spar and coccolith dissolution experiments.Therefore,microbial mediation clearly enhanced calcite mineral dissolution in oversaturated seawater,which likely occurred in the acidic microenvironments produced by bacterial metabolic activity.Linear regression analyses of the DIC and TA revealed that the relative contribution of CaCO3dissolution to organic matter decomposition was 0.18±0.13 and 0.22±0.01,respectively,in the Iceland spar and coccolith experimental groups.The linear regression slope,defined as the OAE-mCDR efficiency indicating the amount of atmospheric CO2absorbed per unit increase in TA,was 3.53±1.87 and 4.36±0.05 for the two groups.Both values exceed a theoretical value of 0.81 under the incubation seawater conditions,primarily driven by DIC increases from organic matter decomposition in the substrate medium.However,microbe-mineral interactions might also improve OAE performance and capabilities.We propose that microbial mediation plays an important role in promoting carbonate mineral dissolution,even in calcite-oversaturated seawater,and can be incorporated into future mCDR implementation strategies.