Dunaliella salina is a classic halophilic alga.However,its molecular mechanisms in response to high salinity at the post transcriptional level remain unknown.A unique halophilic alga strain,DS-CN1,was screened from fo...Dunaliella salina is a classic halophilic alga.However,its molecular mechanisms in response to high salinity at the post transcriptional level remain unknown.A unique halophilic alga strain,DS-CN1,was screened from four D.salina strains via cell biological,physiological,and biochemical methods.High-throughput sequencing of small RNAs(sRNAs)of DS-CN1 in culture medium containing 3.42-mol/L NaCl(SS group)or 0.05-mol/L NaCl(CO group)was performed on the BGISEQ-500 platform.The annotation and sequences of D.salina sRNAs were profiled.Altogether,44 novel salt stress-responsive microRNAs(miRNAs)with a relatively high C content,with the majority of them being 24 nt in length,were identified and characterized in DS-CN1.Twenty-one differentially expressed miRNAs(DEMs)in SS and CO were screened via bioinformatic analysis.A total of 319 putative salt stress-related genes targeted(104 overlapping genes)by novel miRNAs in this alga were screened based on our previous transcriptome sequencing research.Furthermore,these target genes were classified and enriched by GO and KEGG pathway analysis.Moreover,5 novel DEMs(dsa-mir3,dsa-mir16,dsa-mir17,and dsa-mir26 were significantly upregulated,and dsa-mir40 was significantly downregulated)and their corresponding 10 target genes involved in the 6 significantly enriched metabolic pathways were verified by quantitative real-time PCR.Next,their regulatory relationships were comprehensively analyzed.Lastly,a unique salt stress response metabolic network was constructed based on the novel DEM-target gene pairs.Taken together,our results suggest that 44 novel salt stress-responsive microRNAs were identified,and 4 of them might play important roles in D.salina upon salinity stress and contribute to clarify its distinctive halophilic feature.Our study will shed light on the regulatory mechanisms of salt stress responses.展开更多
The present study was conducted to determine the ef fects of elevated pCO_2 on growth, photosynthesis, dark respiration and inorganic carbon acquisition in the marine microalga D unaliella salina. To accomplish this, ...The present study was conducted to determine the ef fects of elevated pCO_2 on growth, photosynthesis, dark respiration and inorganic carbon acquisition in the marine microalga D unaliella salina. To accomplish this, D. salina was incubated in semi-continuous cultures under present-day CO_2 levels(390 μatm, p HN BS : 8.10), predicted year 2100 CO_2 levels(1 000 μatm, p HN BS : 7.78) and predicted year 2300 CO_2 levels(2 000 μatm, p H NBS : 7.49). Elevated pCO_2 significantly enhanced photosynthesis(in terms of gross photosynthetic O_2 evolution, ef fective quantum yield(ΔF/F' m), photosynthetic efficiency( α), maximum relative electron transport rate(r ETRm ax) and ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) activity) and dark respiration of D. salina, but had insignificant effects on growth. The photosynthetic O_2 evolution of D. salina was significantly inhibited by the inhibitors acetazolamide(AZ), ethoxyzolamide(EZ) and 4,4'-diisothiocyanostilbene-2,2′-disulfonate(DIDS), indicating that D. salina is capable of acquiring HCO ˉ 3 via extracellular carbonic anhydrase and anion-exchange proteins. Furthermore, the lower inhibition of the photosynthetic O2 evolution at high pCO_2 levels by AZ, EZ and DIDS and the decreased carbonic anhydrase showed that carbon concentrating mechanisms were down-regulated at high pCO_2. In conclusion, our results show that photosynthesis, dark respiration and CCMs will be af fected by the increased pCO_2/low p H conditions predicted for the future, but that the responses of D. salina to high pCO_2/low p H might be modulated by other environmental factors such as light, nutrients and temperature. Therefore, further studies are needed to determine the interactive eff ects of pCO_2, temperature, light and nutrients on marine microalgae.展开更多
Objective: To investigate the possible protective and/or therapeutic potentials of Dunaliella salina(D. salina) biomass, its carotenoid and polar fractions on cardiac dysfunction associated with D-galactose(D-GAL) ind...Objective: To investigate the possible protective and/or therapeutic potentials of Dunaliella salina(D. salina) biomass, its carotenoid and polar fractions on cardiac dysfunction associated with D-galactose(D-GAL) induced aging in rats. Methods: Aging associated cardiac dysfunction was induced in rats by injection of D-GAL(200 mg/kg; i.p) for 8 weeks. D-GAL injected rats were treated with two regimens; protective regimen where D. salina biomass(250 mg/kg), its carotenoid(250 μg/kg) and polar(250 μg/kg) fractions were given orally for two weeks concurrently with D-GAL injection as well as treatment regimen where the three treatments were given orally for 28 consecutive days after D-GAL injection. Results: D-GAL injection for 8 weeks was accompanied with dramatic electrocardiographic changes as well as profound elevation in serum levels of homocysteine, creatinine kinase isoenzyme and lactate dehydrogenase in addition to the reduction of the cardiac content of glucose trasporter 4. D-GAL also induced reduction in cardiac superoxide dismutase activity and elevation of inducible nitric oxide synthetase and interleukin-6. On the other hand, oral administration of D. salina carotenoid fraction as well as the total biomass significantly attenuated the D-GAL-induced disturbances in the above mentioned parameters where the protective regimen appeared more successful in controlling the manifestations of cardiac dysfunction. The histopathological examination further emphasized the promising results. Besides, the HPLC analysis of the carotenoid fraction of D. salina revealed the presence of 2.31%. salina carotenoid fraction as well as the total biomass amelior β-carotene. Conclusions: Date D-GAL-induced aging associated cardiac dysfunction which is attributed to the potent antioxidant activity of β-carotene.展开更多
Salt stress is an abiotic stress to plants in especially saline lakes.Dunaliella,a halophilic microalga distributed throughout salt lakes and seas,can respond to different salinity stresses by regulating the expressio...Salt stress is an abiotic stress to plants in especially saline lakes.Dunaliella,a halophilic microalga distributed throughout salt lakes and seas,can respond to different salinity stresses by regulating the expression of some genes.However,these genes and their function and biological processes involved remain unclear.Profi ling these salt-stress-related genes in a high-salt-tolerant Dunaliella species will help clarify the salt tolerance machinery of Dunaliella.Three D.salina_YC salt-stress groups were tested under low(0.51 mol/L),moderate(1.03 mol/L),and high(3.42 mol/L)NaCl concentrations and one control group under very low(0.05 mol/L)NaCl concentration and 3 transcriptome results that were deep sequenced and de novo assembled were obtained per group.Twelve high-quality RNA-seq libraries with 46585 upregulated and 47805 downregulated unigenes were found.Relative to the control,188 common differentially expressed genes(DEGs)were screened and divided into four clusters in expression pattern.Fifteen of them annotated in the significant enriched Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)were validated via qPCR.Their qPCR-based relative expression patterns were similar to their RNA-seq-based patterns.Two significant DEGs,the geranylgeranyl diphosphate synthase coding gene(1876-bp cDNA)and diacylglycerol O-acyltransferase coding gene(2968-bp cDNA),were cloned and analyzed in silico.The total lipid content,superoxide dismutase specific activity,and betacarotene content of D.salina_YC increased gradually with increasing salinity.In addition,the expression of 11 validated genes involved in fatty acid biosynthesis/degradation,active oxygen or carotenoid metabolisms showed significant changes.In addition,algal photochemical efficiency was diminished with increasing salinity,as well as the expression of 4 photosynthesis-related genes.These results could help clarify the molecular mechanisms underlying D.salina responses to the Yuncheng Salt Lake environment and lay a foundation for further utilization of this algal resource.展开更多
Algal allelopathy is a manifold ecological/physiological phenomenon that is focused on chemical interactions and autotoxicity. We investigated the allelopathic interactions between Karenia mikimotoi and Dunaliella sal...Algal allelopathy is a manifold ecological/physiological phenomenon that is focused on chemical interactions and autotoxicity. We investigated the allelopathic interactions between Karenia mikimotoi and Dunaliella salina in laboratory cultures based on diff erent temperature(15°C, 20°C, and 25°C) and lighting(40, 80, and 160 μmol/(m^2 ·s)) conditions. The growth of D. salina in bi-algae culture(1:1 size/density) was significantly restrained. The results of cell-free filtrate culture indicate that direct cell-tocell contact was not necessary in interspecific competition. Further experimental results demonstrated that allelochemicals released from K. mikimotoi were markedly influenced by both temperature( P =0.013) and irradiance( P =0.003), resulting in diff erent growth characteristics of D. salina in filtrate mediums. Compared with the plateau period, K. mikimotoi exudates in the exponential phase had a stronger short-term inhibition eff ect on D. salina in normal conditions. A clear concentration-dependent relationship was observed in the eff ect of allelochemicals released from K. mikimotoi with low-promoting and high-repressing eff ects on D. Salina in a short time-scale. In addition, allelopathic substances remain stable and eff ective under high temperature and pressure stress. Many flocculent sediments adhering with D. salina cells were observed in all filtrate mediums, while the quantity and color depended on the original culture conditions.展开更多
Protein kinase C (PKC) has a crucial role in signal transduction for a variety of biologically active substances which activate cellular functions and proliferation. We previously isolated the full-length PKC gene fro...Protein kinase C (PKC) has a crucial role in signal transduction for a variety of biologically active substances which activate cellular functions and proliferation. We previously isolated the full-length PKC gene from Dunaliella salina (DsPKC) using rapid amplification of cDNA ends (RACE) and RT-PCR methods. And we submitted the mRNA sequence of DsPKC gene to NCBI (Genbank No. JN625213). In the present paper, the DsPKC gene open reading frame obtained by PCR was cloned into pGS-21a vector and transformed into Escherichia coli to generate the fusion protein. Bioinformatics analysis revealed that DsPKC gene was a member of serine/threonine kinase with two conserved domains and highly conserved motifs. The DsPKC was highly expressed upon induction with isopropyl-β-d-thiogalactoside (IPTG) at a final concentration of 0.2 mmol L 1 at 37℃. Under salt stress, the fu- sion protein Green Fluorescent Protein (GFP)-DsPKC was transferred from the cytoplasm to the cell membrane. The expression pat- tern of DsPKC gene was analyzed using real-time quantitative PCR, and indicated that DsPKC gene was up-regulated by 3.0 mol L 1 NaCl at 12 h, which was significantly higher than in control values (P < 0.05). These results suggest that the DsPKC gene plays an important role in response to salt stress in D. salina.展开更多
The unicellular halotolerant alga Dunaliella salina had the ability to oxidize NADH and reduce Fe(CN)63-. The redox reactions were to some extent stimulated by slight hyperosmotic shock (2.0 mol/L → 2.6 mol/L NaCl), ...The unicellular halotolerant alga Dunaliella salina had the ability to oxidize NADH and reduce Fe(CN)63-. The redox reactions were to some extent stimulated by slight hyperosmotic shock (2.0 mol/L → 2.6 mol/L NaCl), butmarkably inhibited by abrupt hyperosmotic shock (2.0mol/L → 3.5 mol/L NaCl) and hypoosmotic shock (2.0mol/L → 1.0 mol/L NaCl; 2.0 mol/L→0.67 mol/L NaCl).With the adaptation of algal cells to osmotic shock by accumulating or degrading intracellular glycerol, the plasmalemma redox activities were also restored. The O2 uptake stimulated by NADH could be promoted by FA and SHAM. Hypoosmotic shock increases the basal respiration rate of alga cells, but weakened the stimulating effects of NADH, FA and SHAM on O2 uptake. On the other hand, hyperosmotic shock reduced the basal respiration rate, but relatively enhanced the above effects of NADH, FA and SHAM. H+ extrusion of alga cells was inhibited by NADH and stimulated by Fe(CN)63- Vanadate and DES could inhibit H+ efflux, but had little effect in the presence of NADH and Fe(CN)63-. Both hyperand hypoosmotic shock stimulated H+ extrusion. This effect could be totally inhibited by vanadate and DES, but almost unaffected by 8-hydroxyquinoline. It was suggested that H+-ATPase probably played a more important role in H+ extrusion and osmoregulation under the conditions of osmotic shock.展开更多
The effects of ambient CO2/ambient UV- B, enriched CO2/ambient UV- B, ambient CO2/enhanced UV- B, and enriched CO2/ enhanced UV- B on the ultrastructure of Dunaliella salina were investigated. (1) The ultrastructure o...The effects of ambient CO2/ambient UV- B, enriched CO2/ambient UV- B, ambient CO2/enhanced UV- B, and enriched CO2/ enhanced UV- B on the ultrastructure of Dunaliella salina were investigated. (1) The ultrastructure of D. salina cell in the control experiment showed that the arrangement of thylakoid lamellae was regular, and there were many large starch grains among the thylakoid lamellae. A prominent well-developed pyrenoid was found in the middle of the chloroplast. Nucleus envelope and nucleolus were clearly ob- served. The Golgi apparatus accompanied by numerous vesicles with a compact arrangement of cisternae and the peripheral tips of the cisternae were swollen to a size comparable to that of some of the associated vesicles. (2) The ultrastructure of D. salina cell in en- riched CO2 showed that the arrangement of thylakoid was regular and the lamellae were vivid. Developed pyrenoids were found in the low-CO2-grown cells, but not in the high-CO2-grown cells. The mitochondria cristae were vivid. The arrangement of Golgi apparatus was compact. (3) The ultrastructure of D. salina cell in enhanced UV- B showed that the thylakoid was dissolved and the cells had a less developed pyrenoid or no detectable pyrenoid. Part of the nucleus envelope was dissolved. The number of mitochondria was in- creased and some mitochondria cristae were disintegrated. The starch grains were broken apart into many small starch grains. The Gol- gi apparatus with a loose arrangement of cisternae and the peripheral tips of the Golgi cisternae were not especially swollen, with sev- eral large associated vesicles. (4) The ultrastructure of D. salina cell in the enriched CO2/enhanced UV- B showed that part of the thy- lakoid and nucleus envelopes of some cells were dissolved. The pyrenoid was larger than that of the enhanced UV- B. There were many mitochondria between stroma and chloroplast membrane, but mitochondria cristae were partly dissolved. Many small starch grains were accumulated in cells. The starch sheath was broken into several discontinuous starch grains with different sizes. The ar- rangement of Golgi apparatus was loose. Above all, although the enriched CO2 can alleviate the damage induced by the UV- B radia- tion, the effects of experimental UV- B radiation were larger than the effects of actual UV- B radiation, the damage induced by the UV- B radiation was so severe, therefore, CO2 enrichment could not restore the ultrastructure to the control level.展开更多
The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without...The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without the fluidic oscillator) and non-aerated flask culture. The impact of CO2 mass transfer on Dunaliella salina growth is assessed, through varying the gas (5% CO2, 95% N2) dosing flow rate. The results showed that approximately 6 - 8 times higher chlorophyll content was achieved in the aerated ALB cultures than in the non-aerated flasks, and there was a 20% - 40% increase in specific growth rate of D. salina in the novel ALB with microbubbles when compared with the conventional ALB cultures. The increase in chlorophyll content was found to be proportional to the total amount of CO2 mass transfer. For the same dosing time and flow rate, higher CO2 mass transfer rate (microbubble dosing) resulted in a greater growth rate.展开更多
Plants possess effective mechanisms to respond quickly to the external environment. Rapid activation of phosphatidylinositol-specific phospholipase C (PLC) enzymes occurs after a stimulus. The PLC in Dunaliella salina...Plants possess effective mechanisms to respond quickly to the external environment. Rapid activation of phosphatidylinositol-specific phospholipase C (PLC) enzymes occurs after a stimulus. The PLC in Dunaliella salina plays important roles in growth and stress responses. However, the molecular basis of PLC action in D. salina remains little understood. To gain insight into the potential biological functions of this enzyme, we cloned a phospholipase C gene from D. salina in a previous study, named DsPLC (GenBank No. KF573428). Here, we present the prokaryotic expression, purification, and characterization of the DsPLC gene. The entire coding region of DsPLC was inserted into an expression vector pET32a, and the DsPLC gene was successfully expressed in Escherichia coli. The DsPLC protein was purified and identified using a polyclonal antibody and western blotting. Expressing DsPLC fused with a green fluorescent protein (GFP) in onion showed that DsPLC-GFP was localized to the intracellular membrane. Quantitative real-time PCR analysis revealed that the relative expression of the DsPLC gene was induced significantly by 3.0-mol/L NaCl at 4 h. Our results support the importance of PLC enzymes in plant defense signaling. This study provides a basis for further functional studies of the DsPLC gene and for additional analysis of the potential roles of PLC enzymes in response to abiotic stress.展开更多
基金Supported by the National Natural Science Foundation of China(No.32170204)Science and Technology Strategy Research Special Project of Shanxi Province of China(No.202204031401051)+2 种基金the Basic Research Programs of Shanxi Province of China(No.202103021224009)the Teaching Reform and Innovation Project of Colleges and Universities in Shanxi of China(No.J20220046)the Shanxi“1331 Project”.
文摘Dunaliella salina is a classic halophilic alga.However,its molecular mechanisms in response to high salinity at the post transcriptional level remain unknown.A unique halophilic alga strain,DS-CN1,was screened from four D.salina strains via cell biological,physiological,and biochemical methods.High-throughput sequencing of small RNAs(sRNAs)of DS-CN1 in culture medium containing 3.42-mol/L NaCl(SS group)or 0.05-mol/L NaCl(CO group)was performed on the BGISEQ-500 platform.The annotation and sequences of D.salina sRNAs were profiled.Altogether,44 novel salt stress-responsive microRNAs(miRNAs)with a relatively high C content,with the majority of them being 24 nt in length,were identified and characterized in DS-CN1.Twenty-one differentially expressed miRNAs(DEMs)in SS and CO were screened via bioinformatic analysis.A total of 319 putative salt stress-related genes targeted(104 overlapping genes)by novel miRNAs in this alga were screened based on our previous transcriptome sequencing research.Furthermore,these target genes were classified and enriched by GO and KEGG pathway analysis.Moreover,5 novel DEMs(dsa-mir3,dsa-mir16,dsa-mir17,and dsa-mir26 were significantly upregulated,and dsa-mir40 was significantly downregulated)and their corresponding 10 target genes involved in the 6 significantly enriched metabolic pathways were verified by quantitative real-time PCR.Next,their regulatory relationships were comprehensively analyzed.Lastly,a unique salt stress response metabolic network was constructed based on the novel DEM-target gene pairs.Taken together,our results suggest that 44 novel salt stress-responsive microRNAs were identified,and 4 of them might play important roles in D.salina upon salinity stress and contribute to clarify its distinctive halophilic feature.Our study will shed light on the regulatory mechanisms of salt stress responses.
基金Supported by the Joint Funds of the National Natural Science Foundation of China and the Marine Science Research Center of the People’s Government of Shandong Province(No.U1406403)the National Natural Science Foundation of China(No.41476091)
文摘The present study was conducted to determine the ef fects of elevated pCO_2 on growth, photosynthesis, dark respiration and inorganic carbon acquisition in the marine microalga D unaliella salina. To accomplish this, D. salina was incubated in semi-continuous cultures under present-day CO_2 levels(390 μatm, p HN BS : 8.10), predicted year 2100 CO_2 levels(1 000 μatm, p HN BS : 7.78) and predicted year 2300 CO_2 levels(2 000 μatm, p H NBS : 7.49). Elevated pCO_2 significantly enhanced photosynthesis(in terms of gross photosynthetic O_2 evolution, ef fective quantum yield(ΔF/F' m), photosynthetic efficiency( α), maximum relative electron transport rate(r ETRm ax) and ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco) activity) and dark respiration of D. salina, but had insignificant effects on growth. The photosynthetic O_2 evolution of D. salina was significantly inhibited by the inhibitors acetazolamide(AZ), ethoxyzolamide(EZ) and 4,4'-diisothiocyanostilbene-2,2′-disulfonate(DIDS), indicating that D. salina is capable of acquiring HCO ˉ 3 via extracellular carbonic anhydrase and anion-exchange proteins. Furthermore, the lower inhibition of the photosynthetic O2 evolution at high pCO_2 levels by AZ, EZ and DIDS and the decreased carbonic anhydrase showed that carbon concentrating mechanisms were down-regulated at high pCO_2. In conclusion, our results show that photosynthesis, dark respiration and CCMs will be af fected by the increased pCO_2/low p H conditions predicted for the future, but that the responses of D. salina to high pCO_2/low p H might be modulated by other environmental factors such as light, nutrients and temperature. Therefore, further studies are needed to determine the interactive eff ects of pCO_2, temperature, light and nutrients on marine microalgae.
文摘Objective: To investigate the possible protective and/or therapeutic potentials of Dunaliella salina(D. salina) biomass, its carotenoid and polar fractions on cardiac dysfunction associated with D-galactose(D-GAL) induced aging in rats. Methods: Aging associated cardiac dysfunction was induced in rats by injection of D-GAL(200 mg/kg; i.p) for 8 weeks. D-GAL injected rats were treated with two regimens; protective regimen where D. salina biomass(250 mg/kg), its carotenoid(250 μg/kg) and polar(250 μg/kg) fractions were given orally for two weeks concurrently with D-GAL injection as well as treatment regimen where the three treatments were given orally for 28 consecutive days after D-GAL injection. Results: D-GAL injection for 8 weeks was accompanied with dramatic electrocardiographic changes as well as profound elevation in serum levels of homocysteine, creatinine kinase isoenzyme and lactate dehydrogenase in addition to the reduction of the cardiac content of glucose trasporter 4. D-GAL also induced reduction in cardiac superoxide dismutase activity and elevation of inducible nitric oxide synthetase and interleukin-6. On the other hand, oral administration of D. salina carotenoid fraction as well as the total biomass significantly attenuated the D-GAL-induced disturbances in the above mentioned parameters where the protective regimen appeared more successful in controlling the manifestations of cardiac dysfunction. The histopathological examination further emphasized the promising results. Besides, the HPLC analysis of the carotenoid fraction of D. salina revealed the presence of 2.31%. salina carotenoid fraction as well as the total biomass amelior β-carotene. Conclusions: Date D-GAL-induced aging associated cardiac dysfunction which is attributed to the potent antioxidant activity of β-carotene.
基金Supported by the National Natural Science Foundation of China(No.31670208)the Applied Basic Research Programs of Shanxi Province of China(No.201801D221242)+1 种基金the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi of China(No.2019L0041)the Shanxi“Project 1331”.
文摘Salt stress is an abiotic stress to plants in especially saline lakes.Dunaliella,a halophilic microalga distributed throughout salt lakes and seas,can respond to different salinity stresses by regulating the expression of some genes.However,these genes and their function and biological processes involved remain unclear.Profi ling these salt-stress-related genes in a high-salt-tolerant Dunaliella species will help clarify the salt tolerance machinery of Dunaliella.Three D.salina_YC salt-stress groups were tested under low(0.51 mol/L),moderate(1.03 mol/L),and high(3.42 mol/L)NaCl concentrations and one control group under very low(0.05 mol/L)NaCl concentration and 3 transcriptome results that were deep sequenced and de novo assembled were obtained per group.Twelve high-quality RNA-seq libraries with 46585 upregulated and 47805 downregulated unigenes were found.Relative to the control,188 common differentially expressed genes(DEGs)were screened and divided into four clusters in expression pattern.Fifteen of them annotated in the significant enriched Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)were validated via qPCR.Their qPCR-based relative expression patterns were similar to their RNA-seq-based patterns.Two significant DEGs,the geranylgeranyl diphosphate synthase coding gene(1876-bp cDNA)and diacylglycerol O-acyltransferase coding gene(2968-bp cDNA),were cloned and analyzed in silico.The total lipid content,superoxide dismutase specific activity,and betacarotene content of D.salina_YC increased gradually with increasing salinity.In addition,the expression of 11 validated genes involved in fatty acid biosynthesis/degradation,active oxygen or carotenoid metabolisms showed significant changes.In addition,algal photochemical efficiency was diminished with increasing salinity,as well as the expression of 4 photosynthesis-related genes.These results could help clarify the molecular mechanisms underlying D.salina responses to the Yuncheng Salt Lake environment and lay a foundation for further utilization of this algal resource.
基金Supported by the State Key Laboratory of Satellite Ocean Environment Dynamics(Second Institute of Oceanography,SOA)(No.SOED1418)the Public Science and Technology Research Funds Projects of Ocean(No.201305027)+1 种基金the National Natural Science Foundation of China(No.91128212)the Research Fund for the Doctoral Program of Higher Education of China(No.20110132120025)
文摘Algal allelopathy is a manifold ecological/physiological phenomenon that is focused on chemical interactions and autotoxicity. We investigated the allelopathic interactions between Karenia mikimotoi and Dunaliella salina in laboratory cultures based on diff erent temperature(15°C, 20°C, and 25°C) and lighting(40, 80, and 160 μmol/(m^2 ·s)) conditions. The growth of D. salina in bi-algae culture(1:1 size/density) was significantly restrained. The results of cell-free filtrate culture indicate that direct cell-tocell contact was not necessary in interspecific competition. Further experimental results demonstrated that allelochemicals released from K. mikimotoi were markedly influenced by both temperature( P =0.013) and irradiance( P =0.003), resulting in diff erent growth characteristics of D. salina in filtrate mediums. Compared with the plateau period, K. mikimotoi exudates in the exponential phase had a stronger short-term inhibition eff ect on D. salina in normal conditions. A clear concentration-dependent relationship was observed in the eff ect of allelochemicals released from K. mikimotoi with low-promoting and high-repressing eff ects on D. Salina in a short time-scale. In addition, allelopathic substances remain stable and eff ective under high temperature and pressure stress. Many flocculent sediments adhering with D. salina cells were observed in all filtrate mediums, while the quantity and color depended on the original culture conditions.
基金the functional analysis of PKC signaling pathway involved in response to salt stress of Dunaliella salinathe National Natural Science Foundation of China (No. 31472260)
文摘Protein kinase C (PKC) has a crucial role in signal transduction for a variety of biologically active substances which activate cellular functions and proliferation. We previously isolated the full-length PKC gene from Dunaliella salina (DsPKC) using rapid amplification of cDNA ends (RACE) and RT-PCR methods. And we submitted the mRNA sequence of DsPKC gene to NCBI (Genbank No. JN625213). In the present paper, the DsPKC gene open reading frame obtained by PCR was cloned into pGS-21a vector and transformed into Escherichia coli to generate the fusion protein. Bioinformatics analysis revealed that DsPKC gene was a member of serine/threonine kinase with two conserved domains and highly conserved motifs. The DsPKC was highly expressed upon induction with isopropyl-β-d-thiogalactoside (IPTG) at a final concentration of 0.2 mmol L 1 at 37℃. Under salt stress, the fu- sion protein Green Fluorescent Protein (GFP)-DsPKC was transferred from the cytoplasm to the cell membrane. The expression pat- tern of DsPKC gene was analyzed using real-time quantitative PCR, and indicated that DsPKC gene was up-regulated by 3.0 mol L 1 NaCl at 12 h, which was significantly higher than in control values (P < 0.05). These results suggest that the DsPKC gene plays an important role in response to salt stress in D. salina.
文摘The unicellular halotolerant alga Dunaliella salina had the ability to oxidize NADH and reduce Fe(CN)63-. The redox reactions were to some extent stimulated by slight hyperosmotic shock (2.0 mol/L → 2.6 mol/L NaCl), butmarkably inhibited by abrupt hyperosmotic shock (2.0mol/L → 3.5 mol/L NaCl) and hypoosmotic shock (2.0mol/L → 1.0 mol/L NaCl; 2.0 mol/L→0.67 mol/L NaCl).With the adaptation of algal cells to osmotic shock by accumulating or degrading intracellular glycerol, the plasmalemma redox activities were also restored. The O2 uptake stimulated by NADH could be promoted by FA and SHAM. Hypoosmotic shock increases the basal respiration rate of alga cells, but weakened the stimulating effects of NADH, FA and SHAM on O2 uptake. On the other hand, hyperosmotic shock reduced the basal respiration rate, but relatively enhanced the above effects of NADH, FA and SHAM. H+ extrusion of alga cells was inhibited by NADH and stimulated by Fe(CN)63- Vanadate and DES could inhibit H+ efflux, but had little effect in the presence of NADH and Fe(CN)63-. Both hyperand hypoosmotic shock stimulated H+ extrusion. This effect could be totally inhibited by vanadate and DES, but almost unaffected by 8-hydroxyquinoline. It was suggested that H+-ATPase probably played a more important role in H+ extrusion and osmoregulation under the conditions of osmotic shock.
基金funded by the National Natural Science Foundation of China under contract Nos 30270258 and 40506028the Encouraging Foundation for 0utstanding Youth Scientists of Shandong Province under contract No.03BS120the China Postdoctoral Science Foundation under contract No.2005037237.
文摘The effects of ambient CO2/ambient UV- B, enriched CO2/ambient UV- B, ambient CO2/enhanced UV- B, and enriched CO2/ enhanced UV- B on the ultrastructure of Dunaliella salina were investigated. (1) The ultrastructure of D. salina cell in the control experiment showed that the arrangement of thylakoid lamellae was regular, and there were many large starch grains among the thylakoid lamellae. A prominent well-developed pyrenoid was found in the middle of the chloroplast. Nucleus envelope and nucleolus were clearly ob- served. The Golgi apparatus accompanied by numerous vesicles with a compact arrangement of cisternae and the peripheral tips of the cisternae were swollen to a size comparable to that of some of the associated vesicles. (2) The ultrastructure of D. salina cell in en- riched CO2 showed that the arrangement of thylakoid was regular and the lamellae were vivid. Developed pyrenoids were found in the low-CO2-grown cells, but not in the high-CO2-grown cells. The mitochondria cristae were vivid. The arrangement of Golgi apparatus was compact. (3) The ultrastructure of D. salina cell in enhanced UV- B showed that the thylakoid was dissolved and the cells had a less developed pyrenoid or no detectable pyrenoid. Part of the nucleus envelope was dissolved. The number of mitochondria was in- creased and some mitochondria cristae were disintegrated. The starch grains were broken apart into many small starch grains. The Gol- gi apparatus with a loose arrangement of cisternae and the peripheral tips of the Golgi cisternae were not especially swollen, with sev- eral large associated vesicles. (4) The ultrastructure of D. salina cell in the enriched CO2/enhanced UV- B showed that part of the thy- lakoid and nucleus envelopes of some cells were dissolved. The pyrenoid was larger than that of the enhanced UV- B. There were many mitochondria between stroma and chloroplast membrane, but mitochondria cristae were partly dissolved. Many small starch grains were accumulated in cells. The starch sheath was broken into several discontinuous starch grains with different sizes. The ar- rangement of Golgi apparatus was loose. Above all, although the enriched CO2 can alleviate the damage induced by the UV- B radia- tion, the effects of experimental UV- B radiation were larger than the effects of actual UV- B radiation, the damage induced by the UV- B radiation was so severe, therefore, CO2 enrichment could not restore the ultrastructure to the control level.
文摘The efficiency of a novel microalgal culture system (an airlift loop bioreactor [ALB] engaged with a fluidic oscillator to produce microbubbles) is compared with both a conventional ALB (producing fine bubbles without the fluidic oscillator) and non-aerated flask culture. The impact of CO2 mass transfer on Dunaliella salina growth is assessed, through varying the gas (5% CO2, 95% N2) dosing flow rate. The results showed that approximately 6 - 8 times higher chlorophyll content was achieved in the aerated ALB cultures than in the non-aerated flasks, and there was a 20% - 40% increase in specific growth rate of D. salina in the novel ALB with microbubbles when compared with the conventional ALB cultures. The increase in chlorophyll content was found to be proportional to the total amount of CO2 mass transfer. For the same dosing time and flow rate, higher CO2 mass transfer rate (microbubble dosing) resulted in a greater growth rate.
基金Supported by the National Natural Science Foundation of China(No.31472260)the Key Laboratory of Hydrobiology in Liaoning Province,College of Fisheries and Life Science,Dalian Ocean University
文摘Plants possess effective mechanisms to respond quickly to the external environment. Rapid activation of phosphatidylinositol-specific phospholipase C (PLC) enzymes occurs after a stimulus. The PLC in Dunaliella salina plays important roles in growth and stress responses. However, the molecular basis of PLC action in D. salina remains little understood. To gain insight into the potential biological functions of this enzyme, we cloned a phospholipase C gene from D. salina in a previous study, named DsPLC (GenBank No. KF573428). Here, we present the prokaryotic expression, purification, and characterization of the DsPLC gene. The entire coding region of DsPLC was inserted into an expression vector pET32a, and the DsPLC gene was successfully expressed in Escherichia coli. The DsPLC protein was purified and identified using a polyclonal antibody and western blotting. Expressing DsPLC fused with a green fluorescent protein (GFP) in onion showed that DsPLC-GFP was localized to the intracellular membrane. Quantitative real-time PCR analysis revealed that the relative expression of the DsPLC gene was induced significantly by 3.0-mol/L NaCl at 4 h. Our results support the importance of PLC enzymes in plant defense signaling. This study provides a basis for further functional studies of the DsPLC gene and for additional analysis of the potential roles of PLC enzymes in response to abiotic stress.
