The model diatom Phaeodactylum tricornutum is considered a promising source of various high value bioproducts,and developing cultivation processes is crucial for its commercialization.Although mixotrophy and heterotro...The model diatom Phaeodactylum tricornutum is considered a promising source of various high value bioproducts,and developing cultivation processes is crucial for its commercialization.Although mixotrophy and heterotrophy have been recommended as effective strategies for microalgal cultivation,previous studies on P.tricornutum have yielded conflicting results in terms of cultivating this microalga.To verify the capacity of this microalga utilizing external organic carbon,both heterotrophic and mixotrophic cultivation with varied carbon sources were performed using an axenic strain.The results demonstrate that glycerol was the only organic carbon that substantially stimulated the growth of P.tricornutum in the presence of light.Sodium acetate(NaAc)at low concentrations could also promote growth,while at high concentrations led to severe inhibition under mixotrophic conditions.The addition of glucose imposed no appreciable impact on either cell density or biomass concentration,confirming that P.tricornutum cannot metabolize external glucose.Subsequently,a comparative analysis between mixotrophy and autotrophy was performed to reveal the influences of glycerol on the cellular metabolism based on growth performances,biochemical compositions,and chlorophyll fluorescence parameters.Results also indicate that the addition of glycerol did not have detrimental effects on the capacity of either pigments biosynthesis or photosynthesis,but enhanced the saturated fatty acids and reduced the unsaturated fatty acids.展开更多
PDI is a molecular chaperone and plays an important role in Endoplasmic Reticulum quality control (ERQC).PDI participates in the refolding of the misfolded/unfolded proteins to maintain cellular homeostasis under diff...PDI is a molecular chaperone and plays an important role in Endoplasmic Reticulum quality control (ERQC).PDI participates in the refolding of the misfolded/unfolded proteins to maintain cellular homeostasis under differentstresses. However, bioinformatic characteristics and potential functions of PDIs in diatom Phaeodactylumtricornutum (Pt) are still unknown so far. Hence, the genome-wide characteristics of PtPDI proteins in P. tricornutumwere first studied via bioinformatic and transcriptomic methods. 42 PtPDI genes were identified from thegenome of P. tricornutum. The motif, protein structure, classification, number of introns, phylogenetic relationship,and the expression level of 42 PtPDI genes under the tunicamycin stress were analyzed. A pair of tandemduplicated genes (PtPDI15 and PtPDI18) was observed in P. tricornutum. The 42 PtPDIs with different genecharacteristics were divided into three independent clades, indicating different evolutional relationships and functionsof these PtPDIs. The 14 up-regulated PtPDI genes under the tunicamycin treatment might have a positiveeffect on the ER quality control of the unfolded/misfolded proteins, while the 7 down-regulated PtPDIs mightnegatively affect the ERQC. The characteristics of all 42 PtPDIs and their proposed working model here providea comprehensive understanding of the PtPDIs gene family. The differential expression of 21 PtPDIs will be usefulfor further functional study in the ERQC.展开更多
Light regulates important metabolic processes in microalgal cells, which can further impact the metabolism and the accumulation of biomolecules such as lipids, carbohydrates, and proteins. Different characteristics of...Light regulates important metabolic processes in microalgal cells, which can further impact the metabolism and the accumulation of biomolecules such as lipids, carbohydrates, and proteins. Different characteristics of light have been studied on various strains of the model diatom Phaeodactylum tricornutum, but not on transconjugant cells and information on wild-type strains is still limited. Therefore, we studied the impact of different light characteristics such as spectral quality, light intensity and light shift on the growth, and the composition in lipids and fatty acids of P. tricornutum cells to provide a comprehensive context for future applications. Initially, we tested the impact of spectral quality and light intensity on P. tricornutum transformed with an episomal vector (Ptev), harboring the resistance gene Sh ble. Results indicated that Ptev cells accumulated more biomass and overall lipids in spectral quality Red 1 (R1: 34% > 600 nm > 66%) more effectively as compared to Red 2 (R2: 8% > 600 nm > 92%). It was also detected that cell granularity was higher in R1 as compared to R2. Furthermore, by testing two light intensities 65 μmol·m<sup>-2</sup>·s<sup>-1</sup> and 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> light, it was observed that 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> led to an increase in growth trend, total biomass and lipid content. Combining spectral qualities and light intensities, we show that the lipid accumulation raised by 2.8-fold. Studying the light intensity and spectral quality allowed us to optimize the light conditions to R1 spectral quality and light intensity 145 μmol·m<sup>-2</sup>·s<sup>-1</sup>. These initial results showed that red light R1 at 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> was the best condition for biomass and total lipids accumulation in Ptev cells. Next, we further combined these two-light optimizations with a third light characteristics, i.e. light shift, where the cultures were shifted during the early stationary phase to a different light environment. We studied Red light shift (Rs) to investigate how light condition variations impacted P. tricornutum transconjugants Ptev and with an episomal vector containing the reporter gene YFP (PtYFP). We observed that Rs induced growth and fatty acid eicosapentaenoic acid (EPA) in Ptev as compared to PtYFP. Altogether, the study shows that red light shift of R1 at 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> promoted biomass and total lipids accumulation in Ptev and PtYFP cells. The study provides a comprehensive approach to using different light characteristics with the aim to optimize growth and lipids, as well as to fatty acid production.展开更多
Phaeodactylum tricornutum is a potential livestock for the combined production of eicosapentaenoic acid(EPA) and fucoxanthin. In this study, six marine diatom strains identified as P. tricornutum were cultured and the...Phaeodactylum tricornutum is a potential livestock for the combined production of eicosapentaenoic acid(EPA) and fucoxanthin. In this study, six marine diatom strains identified as P. tricornutum were cultured and their total lipid, fatty acid composition and major photosynthetic pigments determined. It was found that the cell dry weight concentration and mean growth rate ranged between 0.24–0.36 g/L and 0.31–0.33/d, respectively. Among the strains, SCSIO771 presented the highest total lipid content, followed by SCSIO828, and the prominent fatty acids in all strains were C16:0, C16:1, C18:1, and C20:5(EPA). Polyunsaturated fatty acids, including C16:2, C18:2, and EPA, comprised a significant proportion of the total fatty acids. EPA was markedly high in all strains, with the highest in SCSIO828 at 25.65% of total fatty acids. Fucoxanthin was the most abundant pigment in all strains, with the highest in SCSIO828 as well, at 5.50 mg/g. The collective results suggested that strain SCSIO828 could be considered a good candidate for the concurrent production of EPA and fucoxanthin.展开更多
Specific bacterial communities interact with phytoplankton in laboratory algal cultures. These communities influence phytoplankton physiology and metabolism by transforming and exchanging phytoplankton-derived organic...Specific bacterial communities interact with phytoplankton in laboratory algal cultures. These communities influence phytoplankton physiology and metabolism by transforming and exchanging phytoplankton-derived organic matter. Functional bacterial groups may participate in various critical nutrients fluxes within these associations, including nitrogen(N) metabolism. However, it is unclear how bacterial communities and the associated algae respond to changes of phycosphere N conditions. This response may have far-reaching implications for global nutrient cycling, algal bloom formation, and ecosystem function. Here, we identified changes in the bacterial communities associated with Phaeodactylum tricornutum when co-cultured with different forms and concentrations of N based on the Illumina HiSeq sequencing of 16 S rRNA amplicons.Phylogenetic analysis identified Proteobacteria and Bacteroidetes as the dominant phyla, accounting for 99.5% of all sequences. Importantly, bacterial abundance and community structure were more affected by algal abundance than by the form or concentration of inorganic N. The relative abundance of three gammaproteobacterial genera(Marinobacter, Algiphilus and Methylophaga) markedly increased in N-deficient cultures. Thus, some bacterial groups may play a role in the regulation of N metabolism when co-cultured with P.tricornutum.展开更多
Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production. Its reproduction has profound significance in the life cycle; however, the nuclear behavior during its sexual reproducti...Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production. Its reproduction has profound significance in the life cycle; however, the nuclear behavior during its sexual reproduction was not clear. In this study, we observed the nuclear transition and determined its correlation with cell conjunction. It was found that two cells jointed at their apices first and swung and aligned each other immediately, and nucleus from one cell was able to transfer into another one during cell conjugation. The cell pairs conjugated for nuclear transition were different from those formed in mitosis in hypovalve thickness and cellular arrangement. Our findings proved the existence of sexual reproduction in P. tricornutum.展开更多
A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the ...A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the protective responses of these photosystems to heavy metal stress remain unclear. Using the model diatom P haeodactylum tricornutum, a biological indicator that is widely used to assess the impact of environmental toxins, we simultaneously measured the effects of Cd on PSI and PSII and examined the levels of pigments in response to high light treatments before and after Cd exposure. Cd significantly reduced the quantum yield and electron transport rates of PSI and PSII. The quantum yield of non-photochemical energy dissipation in PSI due to donor side limitation increased faster than the quantum yield due to acceptor side limitation. The Cd treatment activated the P. tricornutum xanthophyll cycle under artificial light conditions, as indicated by an increased diatoxanthin content. Xanthophyll is important for photoprotection; therefore, the accumulation of diatoxanthin may down-regulate PSII activities to reduce oxidative damage. Together, our results suggest that the rapid reduction in PSII activities following Cd exposure is an adaptive response to heavy metal stress that reflects the variable exposure to external stressors in the native P. tricornutum environment.展开更多
Diatoms are important contributors to global net primary productivity,and play a crucial role in the biogeochemical cycles of carbon,phosphorus,nitrogen,iron,and silicon.Currently in some regions in the ocean,there’s...Diatoms are important contributors to global net primary productivity,and play a crucial role in the biogeochemical cycles of carbon,phosphorus,nitrogen,iron,and silicon.Currently in some regions in the ocean,there’s a trend that carbon content is high while oxygen concentration is low,and the underlying mechanisms of diatoms’response to low oxygen environments are worth investigating.Phaeodactylum tricornutum is a model diatom whose genome has been sequenced;it provides a universal molecular toolbox and a stable transgenic expression system.Therefore,the study of the responses of P.tricornutum to low oxygen has not only fundamental research significance but also important ecologic al significance.In this study,growth rates were determined and proteomic analysis and metabolomic analysis were performed to examine P.tricornutum responses under different oxygen concentrations(2%oxygen concentration for hypoxic condition and 21%oxygen concentration for the normal condition(sterilized air)).Results show that the hypoxic environment inhibited the growth of P.tricornutum.In the hypoxic conditions,P.tricornutum could reset its metabolism pathways,including enhancement in lipid utilization,replenishment of tricarboxylic acid(TCA)cycle through the glyoxylic acid cycle,and down-regulation of photorespiration to reduce energy waste.Additionally,the stress resistance mechanism was activated to facilitate the adaptation to low oxygen conditions.This study helps to reveal the different metabolic changes to hypoxia of diatom from that of higher plants,which might be ascribed to their different habitats and needs further exploration in the future.展开更多
Phaeodactylum tricornutum is a diatom that is rich in lipids. Recently, it has received much attention as a feedstock for biodiesel production. Nitrogen deficiency is widely known to increase the content of neutral li...Phaeodactylum tricornutum is a diatom that is rich in lipids. Recently, it has received much attention as a feedstock for biodiesel production. Nitrogen deficiency is widely known to increase the content of neutral lipids (mainly triacylglycerides, or TAGs) of microalgae, including P. tricornutum, but the mechanism is unclear. In this study, we deciphered the correlations between TAG content and nine key enzymatic genes involved in lipid synthesis in P. tricornuturn. After being cultured under nitrogen-free conditions for 0, 4, 24, 48, 72, 120, and 168 h, the TAG contents ofP. tricornutum cells were assayed and the transcript abundances of the target genes were monitored by quantitative real-time PCR. The results show that the abundances of four target gene transcripts (LACS3, G3PDH2, G3PDH3, and G3PDH5) were positively correlated with TAG content, indicating that these genes may be involved in TAG synthesis in P. tricornutum. The findings improve our understanding of the metabolic network and regulation of lipid synthesis and will guide the future genetic improvement of the TAG content ofP. tricornutum.展开更多
Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our ...Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our work in 2019 concerning the ecotoxicological effects of such formulations on corals (Seriatopora hystrix), we here provide some new information about the biodegradability and the ecotoxicological effects of these products on marine zoo- and phytoplankton. Therefore, we choose to realize in silico and in vitro studies of the biodegradability of several solar products but also to evaluate the ecotoxicological effects of these products on one phytoplankton, i.e. Phaeodactylum tricornutum, and one zooplankton, i.e. Acartia tonsa, of a great importance for sea species survival (notably as sources of food). Materials and methods: Two different approaches were used to study the biodegradability of the tested products: One in silico method and an in vitro one. 2 solar products were involved in the in silico study which consisted in the determination of the degradation factor (DF) of each ingredient of the tested formulas in order to finally obtain their estimated biodegradability percentage. Already available data concerning each ingredient coupled to a computer model developed with one of our partners were used to achieve this study. The in vitro study involved 8 formulas containing UV-filters and was led by following the OECD 301 F guidelines. Ecotoxicological studies of 7 of the formulas containing UV-filters were for their part realized by following the ISO 10253 guidelines for the experiments led with Phaeodactylum tricornutum, and the ISO 14669 guidelines for the experiments led with Acartia tonsa. In these studies, the effect of each tested product on crustaceans’ mortality and algal growth inhibition was assessed. Results: The in silico study predicted that formulas containing chemical UV-filters display a high biodegradability (superior to the threshold value of 60% given by the OECD 301 F guidelines). In the in vitro part of our work, the 8 tested formulas showed a biodegradability slightly inferior to the one predicted in the in silico experiments. Therefore, in order to evaluate if these calculated biodegradability value could have significant harmful effects on zoo- or phytoplankton, we studied the effect of our products regarding the growth inhibition on Phaeodactylum tricornutum and the mortality on Acartia tonsa. In this last part of the study, all the tested products were classified as “non ecotoxic” following an internal classification based on Part 4 entitled “Environmental Hazards” of Globally Harmonized System of Classification and Labelling of Chemicals (GHS), 9<sup>th</sup> edition (2021). Conclusions: These results are notably in line with those published by our teams in 2019 on the effects of solar cosmetic products on corals and seem to confirm that formulas containing mineral and chemical UV-filters can be daily used without displaying significant noxious effects on marine fauna and flora. .展开更多
基金Supported by the National Science and Technology Basic Resources Investigation Program of China(No.2018 FY100206)the National Natural Science Foundation of China(No.31902370)+1 种基金the Ningbo Public Welfare Science and Technology Program(No.2022S161)the Key Program of Science and Technology Innovation in Ningbo(No.2023Z118)。
文摘The model diatom Phaeodactylum tricornutum is considered a promising source of various high value bioproducts,and developing cultivation processes is crucial for its commercialization.Although mixotrophy and heterotrophy have been recommended as effective strategies for microalgal cultivation,previous studies on P.tricornutum have yielded conflicting results in terms of cultivating this microalga.To verify the capacity of this microalga utilizing external organic carbon,both heterotrophic and mixotrophic cultivation with varied carbon sources were performed using an axenic strain.The results demonstrate that glycerol was the only organic carbon that substantially stimulated the growth of P.tricornutum in the presence of light.Sodium acetate(NaAc)at low concentrations could also promote growth,while at high concentrations led to severe inhibition under mixotrophic conditions.The addition of glucose imposed no appreciable impact on either cell density or biomass concentration,confirming that P.tricornutum cannot metabolize external glucose.Subsequently,a comparative analysis between mixotrophy and autotrophy was performed to reveal the influences of glycerol on the cellular metabolism based on growth performances,biochemical compositions,and chlorophyll fluorescence parameters.Results also indicate that the addition of glycerol did not have detrimental effects on the capacity of either pigments biosynthesis or photosynthesis,but enhanced the saturated fatty acids and reduced the unsaturated fatty acids.
基金the funding of Educational and Scientific Research Projects for Young and Middle-Aged Teachers in Fujian Province(Grant Number:2022JAT220693)Natural Science Foundation of Guangdong Province(Grant Number:2022A1515012141)+2 种基金the Program for University Innovation Team of Guangdong Province(Grant Number:2022KCXTD008)National Natural Science Foundation of China(92158201 and 42376001)the Innovation and Entrepreneurship Project of Shantou(201112176541391).
文摘PDI is a molecular chaperone and plays an important role in Endoplasmic Reticulum quality control (ERQC).PDI participates in the refolding of the misfolded/unfolded proteins to maintain cellular homeostasis under differentstresses. However, bioinformatic characteristics and potential functions of PDIs in diatom Phaeodactylumtricornutum (Pt) are still unknown so far. Hence, the genome-wide characteristics of PtPDI proteins in P. tricornutumwere first studied via bioinformatic and transcriptomic methods. 42 PtPDI genes were identified from thegenome of P. tricornutum. The motif, protein structure, classification, number of introns, phylogenetic relationship,and the expression level of 42 PtPDI genes under the tunicamycin stress were analyzed. A pair of tandemduplicated genes (PtPDI15 and PtPDI18) was observed in P. tricornutum. The 42 PtPDIs with different genecharacteristics were divided into three independent clades, indicating different evolutional relationships and functionsof these PtPDIs. The 14 up-regulated PtPDI genes under the tunicamycin treatment might have a positiveeffect on the ER quality control of the unfolded/misfolded proteins, while the 7 down-regulated PtPDIs mightnegatively affect the ERQC. The characteristics of all 42 PtPDIs and their proposed working model here providea comprehensive understanding of the PtPDIs gene family. The differential expression of 21 PtPDIs will be usefulfor further functional study in the ERQC.
文摘Light regulates important metabolic processes in microalgal cells, which can further impact the metabolism and the accumulation of biomolecules such as lipids, carbohydrates, and proteins. Different characteristics of light have been studied on various strains of the model diatom Phaeodactylum tricornutum, but not on transconjugant cells and information on wild-type strains is still limited. Therefore, we studied the impact of different light characteristics such as spectral quality, light intensity and light shift on the growth, and the composition in lipids and fatty acids of P. tricornutum cells to provide a comprehensive context for future applications. Initially, we tested the impact of spectral quality and light intensity on P. tricornutum transformed with an episomal vector (Ptev), harboring the resistance gene Sh ble. Results indicated that Ptev cells accumulated more biomass and overall lipids in spectral quality Red 1 (R1: 34% > 600 nm > 66%) more effectively as compared to Red 2 (R2: 8% > 600 nm > 92%). It was also detected that cell granularity was higher in R1 as compared to R2. Furthermore, by testing two light intensities 65 μmol·m<sup>-2</sup>·s<sup>-1</sup> and 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> light, it was observed that 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> led to an increase in growth trend, total biomass and lipid content. Combining spectral qualities and light intensities, we show that the lipid accumulation raised by 2.8-fold. Studying the light intensity and spectral quality allowed us to optimize the light conditions to R1 spectral quality and light intensity 145 μmol·m<sup>-2</sup>·s<sup>-1</sup>. These initial results showed that red light R1 at 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> was the best condition for biomass and total lipids accumulation in Ptev cells. Next, we further combined these two-light optimizations with a third light characteristics, i.e. light shift, where the cultures were shifted during the early stationary phase to a different light environment. We studied Red light shift (Rs) to investigate how light condition variations impacted P. tricornutum transconjugants Ptev and with an episomal vector containing the reporter gene YFP (PtYFP). We observed that Rs induced growth and fatty acid eicosapentaenoic acid (EPA) in Ptev as compared to PtYFP. Altogether, the study shows that red light shift of R1 at 145 μmol·m<sup>-2</sup>·s<sup>-1</sup> promoted biomass and total lipids accumulation in Ptev and PtYFP cells. The study provides a comprehensive approach to using different light characteristics with the aim to optimize growth and lipids, as well as to fatty acid production.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences(No.SQ201213)the National Natural Science Foundation of China(No.31402320)+1 种基金the Guangdong Province and Chinese Academy of Science Cooperation Foundation(No.2012B091100268)the Technology Project of Ocean and Fisheries of Guangdong Province(No.A201101I04)
文摘Phaeodactylum tricornutum is a potential livestock for the combined production of eicosapentaenoic acid(EPA) and fucoxanthin. In this study, six marine diatom strains identified as P. tricornutum were cultured and their total lipid, fatty acid composition and major photosynthetic pigments determined. It was found that the cell dry weight concentration and mean growth rate ranged between 0.24–0.36 g/L and 0.31–0.33/d, respectively. Among the strains, SCSIO771 presented the highest total lipid content, followed by SCSIO828, and the prominent fatty acids in all strains were C16:0, C16:1, C18:1, and C20:5(EPA). Polyunsaturated fatty acids, including C16:2, C18:2, and EPA, comprised a significant proportion of the total fatty acids. EPA was markedly high in all strains, with the highest in SCSIO828 at 25.65% of total fatty acids. Fucoxanthin was the most abundant pigment in all strains, with the highest in SCSIO828 as well, at 5.50 mg/g. The collective results suggested that strain SCSIO828 could be considered a good candidate for the concurrent production of EPA and fucoxanthin.
基金The National Natural Science Foundation of China(NSFC)under contract No.31470536the National Key Research and Development Program of China under contract No.2018YFC1406403
文摘Specific bacterial communities interact with phytoplankton in laboratory algal cultures. These communities influence phytoplankton physiology and metabolism by transforming and exchanging phytoplankton-derived organic matter. Functional bacterial groups may participate in various critical nutrients fluxes within these associations, including nitrogen(N) metabolism. However, it is unclear how bacterial communities and the associated algae respond to changes of phycosphere N conditions. This response may have far-reaching implications for global nutrient cycling, algal bloom formation, and ecosystem function. Here, we identified changes in the bacterial communities associated with Phaeodactylum tricornutum when co-cultured with different forms and concentrations of N based on the Illumina HiSeq sequencing of 16 S rRNA amplicons.Phylogenetic analysis identified Proteobacteria and Bacteroidetes as the dominant phyla, accounting for 99.5% of all sequences. Importantly, bacterial abundance and community structure were more affected by algal abundance than by the form or concentration of inorganic N. The relative abundance of three gammaproteobacterial genera(Marinobacter, Algiphilus and Methylophaga) markedly increased in N-deficient cultures. Thus, some bacterial groups may play a role in the regulation of N metabolism when co-cultured with P.tricornutum.
基金supported by the State Basic Research and Development Program of China (973 Program) (2011-CB200901)the Promotive Research Fund for Excellent Young and Middle-aged Scientists of Shandong Province(BS2010SW037)the Opening Research Project of Experimental Marine Biology Laboratory,Institute of Oceanology,Chinese Academy of Sciences
文摘Phaeodactylum tricornutum is one of the important marine diatoms for oceanic primary production. Its reproduction has profound significance in the life cycle; however, the nuclear behavior during its sexual reproduction was not clear. In this study, we observed the nuclear transition and determined its correlation with cell conjunction. It was found that two cells jointed at their apices first and swung and aligned each other immediately, and nucleus from one cell was able to transfer into another one during cell conjugation. The cell pairs conjugated for nuclear transition were different from those formed in mitosis in hypovalve thickness and cellular arrangement. Our findings proved the existence of sexual reproduction in P. tricornutum.
基金Supported by the National Natural Science Foundation of China(No.41506172)the International S&T Cooperation Program of China(No.2015DFG32160)
文摘A bstract Cadmium(Cd) is one of the most common and widespread heavy metals in the environment. Cd has adverse effects on photosynthesis that are countered by photosystem I(PSI) and photosystem II(PSII); however, the protective responses of these photosystems to heavy metal stress remain unclear. Using the model diatom P haeodactylum tricornutum, a biological indicator that is widely used to assess the impact of environmental toxins, we simultaneously measured the effects of Cd on PSI and PSII and examined the levels of pigments in response to high light treatments before and after Cd exposure. Cd significantly reduced the quantum yield and electron transport rates of PSI and PSII. The quantum yield of non-photochemical energy dissipation in PSI due to donor side limitation increased faster than the quantum yield due to acceptor side limitation. The Cd treatment activated the P. tricornutum xanthophyll cycle under artificial light conditions, as indicated by an increased diatoxanthin content. Xanthophyll is important for photoprotection; therefore, the accumulation of diatoxanthin may down-regulate PSII activities to reduce oxidative damage. Together, our results suggest that the rapid reduction in PSII activities following Cd exposure is an adaptive response to heavy metal stress that reflects the variable exposure to external stressors in the native P. tricornutum environment.
基金Supported by the National Natural Science Foundation of China(Nos.41876158,31770024)the Natural Science Foundation of Hainan Province(No.420QN219)+3 种基金the Biology and Biochemistry ESI Cultivation Discipline Open Project of Qilu University of Technology(No.ESIBBC202004)the Innovation and Development Joint Fund of Natural Science Foundation from Shandong Province(No.ZR2021LSW022)the Young Taishan Scholarship to Xuekui XIA(No.tsqn202103100)the Start-up Fund Project of Hainan University(No.KYQD(ZR)20060)。
文摘Diatoms are important contributors to global net primary productivity,and play a crucial role in the biogeochemical cycles of carbon,phosphorus,nitrogen,iron,and silicon.Currently in some regions in the ocean,there’s a trend that carbon content is high while oxygen concentration is low,and the underlying mechanisms of diatoms’response to low oxygen environments are worth investigating.Phaeodactylum tricornutum is a model diatom whose genome has been sequenced;it provides a universal molecular toolbox and a stable transgenic expression system.Therefore,the study of the responses of P.tricornutum to low oxygen has not only fundamental research significance but also important ecologic al significance.In this study,growth rates were determined and proteomic analysis and metabolomic analysis were performed to examine P.tricornutum responses under different oxygen concentrations(2%oxygen concentration for hypoxic condition and 21%oxygen concentration for the normal condition(sterilized air)).Results show that the hypoxic environment inhibited the growth of P.tricornutum.In the hypoxic conditions,P.tricornutum could reset its metabolism pathways,including enhancement in lipid utilization,replenishment of tricarboxylic acid(TCA)cycle through the glyoxylic acid cycle,and down-regulation of photorespiration to reduce energy waste.Additionally,the stress resistance mechanism was activated to facilitate the adaptation to low oxygen conditions.This study helps to reveal the different metabolic changes to hypoxia of diatom from that of higher plants,which might be ascribed to their different habitats and needs further exploration in the future.
基金Supported by the National Basic Research Program of China(973 Program)(No.2011CB200901)the National Key Technology Research and Development Program(No.2011BAD14B01)+1 种基金the Promotive Research Fund for Excellent Young and Middle-Aged Scientists of Shandong Province(No.BS2010SW037)the National Natural Science Foundation of China(No.31270408)
文摘Phaeodactylum tricornutum is a diatom that is rich in lipids. Recently, it has received much attention as a feedstock for biodiesel production. Nitrogen deficiency is widely known to increase the content of neutral lipids (mainly triacylglycerides, or TAGs) of microalgae, including P. tricornutum, but the mechanism is unclear. In this study, we deciphered the correlations between TAG content and nine key enzymatic genes involved in lipid synthesis in P. tricornuturn. After being cultured under nitrogen-free conditions for 0, 4, 24, 48, 72, 120, and 168 h, the TAG contents ofP. tricornutum cells were assayed and the transcript abundances of the target genes were monitored by quantitative real-time PCR. The results show that the abundances of four target gene transcripts (LACS3, G3PDH2, G3PDH3, and G3PDH5) were positively correlated with TAG content, indicating that these genes may be involved in TAG synthesis in P. tricornutum. The findings improve our understanding of the metabolic network and regulation of lipid synthesis and will guide the future genetic improvement of the TAG content ofP. tricornutum.
文摘Background: Cosmetic formulations, and particularly solar products which contain mineral and chemical UV-filters, are often suspected of causing harmful effects on marine fauna and flora. After the publication of our work in 2019 concerning the ecotoxicological effects of such formulations on corals (Seriatopora hystrix), we here provide some new information about the biodegradability and the ecotoxicological effects of these products on marine zoo- and phytoplankton. Therefore, we choose to realize in silico and in vitro studies of the biodegradability of several solar products but also to evaluate the ecotoxicological effects of these products on one phytoplankton, i.e. Phaeodactylum tricornutum, and one zooplankton, i.e. Acartia tonsa, of a great importance for sea species survival (notably as sources of food). Materials and methods: Two different approaches were used to study the biodegradability of the tested products: One in silico method and an in vitro one. 2 solar products were involved in the in silico study which consisted in the determination of the degradation factor (DF) of each ingredient of the tested formulas in order to finally obtain their estimated biodegradability percentage. Already available data concerning each ingredient coupled to a computer model developed with one of our partners were used to achieve this study. The in vitro study involved 8 formulas containing UV-filters and was led by following the OECD 301 F guidelines. Ecotoxicological studies of 7 of the formulas containing UV-filters were for their part realized by following the ISO 10253 guidelines for the experiments led with Phaeodactylum tricornutum, and the ISO 14669 guidelines for the experiments led with Acartia tonsa. In these studies, the effect of each tested product on crustaceans’ mortality and algal growth inhibition was assessed. Results: The in silico study predicted that formulas containing chemical UV-filters display a high biodegradability (superior to the threshold value of 60% given by the OECD 301 F guidelines). In the in vitro part of our work, the 8 tested formulas showed a biodegradability slightly inferior to the one predicted in the in silico experiments. Therefore, in order to evaluate if these calculated biodegradability value could have significant harmful effects on zoo- or phytoplankton, we studied the effect of our products regarding the growth inhibition on Phaeodactylum tricornutum and the mortality on Acartia tonsa. In this last part of the study, all the tested products were classified as “non ecotoxic” following an internal classification based on Part 4 entitled “Environmental Hazards” of Globally Harmonized System of Classification and Labelling of Chemicals (GHS), 9<sup>th</sup> edition (2021). Conclusions: These results are notably in line with those published by our teams in 2019 on the effects of solar cosmetic products on corals and seem to confirm that formulas containing mineral and chemical UV-filters can be daily used without displaying significant noxious effects on marine fauna and flora. .