Structural parameters of 22 halogen phenols were computed at four levels using Hartree-Fock and DFT methods. Based on the experimental data of the acute toxicity to Tetrahymena pyriformis （-lgEC_50）, three-parameter...Structural parameters of 22 halogen phenols were computed at four levels using Hartree-Fock and DFT methods. Based on the experimental data of the acute toxicity to Tetrahymena pyriformis （-lgEC_50）, three-parameter （energy of the lowest unoccupied molecular orbital （E_LUMO）, the molecular volume （V）, and the lowest negative charge （Q_min）） dependent equations were developed using structural parameters as theoretical descriptors. Especially, -lgEC_50dependent equation calculated at the B3LYP/6-31G^＊＊ level is more advantageous than the others in view of their correlation and predictive abilities. This dependent equation was validated by variance inflation factors （VIF） and t-test methods. Upon comparison, the predictive abilities of our work are all more advantageous than those calculated from the semi-empirical PM3 method.展开更多
The IGC 50 (50% inhibitory growth concentration) values of 27 nitrobenzenes were determined for the population growth endpoint of Tetrahymena pyriformis . The toxicity order of the observed compounds was found to be a...The IGC 50 (50% inhibitory growth concentration) values of 27 nitrobenzenes were determined for the population growth endpoint of Tetrahymena pyriformis . The toxicity order of the observed compounds was found to be as follows: dinitro compounds>mononitro compounds, dichloronitrobenzenes>monochloronitrobenzenes, meta substituted nitrobenzenes>ortho /para substituted nitrobenzenes(NT, NPh, NAnis) except for the dinitrobenzenes and nitroanilines(DNB, NAn). Quantitative structure activity relationships(QSARs) were developed with the logarithm of the reciprocal of IGC 50 [lg(IGC 50 ) -1 ] in mole liter as dependent variable and six molecular descriptors lg P , 1 X Ⅴ, I, 1K a, ∑σ - and E LUMO as independent variables. Via multiple regression analysis, one best equation was obtained: lg(IGC 50 ) -1 =3.029+0.860∑ σ -+0.341I n=27, r=0.924, r 2=0.854, s=0.265, f=70.44 , Pr> f =0.000 1 The equation was used to estimate IGC 50 for five analogues.展开更多
Autophagy is a major cellular pathway used to degrade long-lived proteins or organelles that may be damaged due to increased reactive oxygen species（ROS） generated by cellular stress. Autophagy typically enhances ce...Autophagy is a major cellular pathway used to degrade long-lived proteins or organelles that may be damaged due to increased reactive oxygen species（ROS） generated by cellular stress. Autophagy typically enhances cell survival, but it may also act to promote cell death under certain conditions. The mechanism underlying this paradox, however, remains unclear. We showed that Tetrahymena cells exerted increased membranebound vacuoles characteristic of autophagy followed by autophagic cell death（referred to as cell death with autophagy） after exposure to hydrogen peroxide. Inhibition of autophagy by chloroquine or 3-methyladenine significantly augmented autophagic cell death induced by hydrogen peroxide. Blockage of the mitochondrial electron transport chain or starvation triggered activation of autophagy followed by cell death by inducing the production of ROS due to the loss of mitochondrial membrane potential. This indicated a regulatory role of mitochondrial ROS in programming autophagy and autophagic cell death in Tetrahymena. Importantly, suppression of autophagy enhanced autophagic cell death in Tetrahymena in response to elevated ROS production from starvation, and this was reversed by antioxidants. Therefore, our results suggest that autophagy was activated upon oxidative stress to prevent the initiation of autophagic cell death in Tetrahymena until the accumulation of ROS passed the point of no return, leading to delayed cell death in Tetrahymena.展开更多
Objective To explore the active components with toxic effects in five Aconitum L. herbal medicines on Tetrahymena thermophila. Methods The fingerprints of five Aconitum L. herbal medicines were established by ultra-hi...Objective To explore the active components with toxic effects in five Aconitum L. herbal medicines on Tetrahymena thermophila. Methods The fingerprints of five Aconitum L. herbal medicines were established by ultra-high performance liquid chromatography （UPLC） and the toxicity was evaluated by using a TAM Air Isothermal Calorimeter on Tetrahymena thermophila SB1 10. Results By analyzing the spectrum- effect relationships between UPLC fingerprints and toxic effects, the active components which had the toxic effects were obtained. Conclusion This work provides a general model of the combination of UPLC and microcalorimetry to study the spectrum-effect relationships of the five Aconitum L. herbal medicines, which could be used to evaluate the toxic effects and analyze the principal toxic components of the five Aconitum L. herbal medicines. On the whole, this result provides the experimental basis for the safe use of the five Aconitum L. herbal medicines in clinic.展开更多
The growth therrnogenic curves of Staphylococcus aureus and Tetrahymena thermophila affected by 1,8-dihydroxyanthraquinone, emodin and rhein were determined quantitatively by microcalorimetry. The inhibitory effects o...The growth therrnogenic curves of Staphylococcus aureus and Tetrahymena thermophila affected by 1,8-dihydroxyanthraquinone, emodin and rhein were determined quantitatively by microcalorimetry. The inhibitory effects of the three anthraquinones （AQ） on S. aureus revealed that the sequence of antimicrobial activity of those was rhein〉emodin〉 1,8-dihydroxyanthraquinone. The toxicity of the three AQ on T. thermophila indicated that all the tested AQ were toxic to the tested protozoa and the hydroxyl and carboxyl substituted at different position of anthraquinone ring resulted in the enhancement of toxicity.展开更多
The molecular electronegativity interaction vector （MEIV） was used to describe the molecular structure of 30 selected esters. Two excellent QSTR models were built up by using multiple linear regression （MLR） and p...The molecular electronegativity interaction vector （MEIV） was used to describe the molecular structure of 30 selected esters. Two excellent QSTR models were built up by using multiple linear regression （MLR） and partial least-squares regression （PLS）. The correlation coefficients （R） of the two models were 0.945 and 0.941, respectively. The models were evaluated by performing the cross validation with the leave-one-out （LOO） procedure. The cross-verification correlation coefficients （RCV） of the two models were 0.921 and 0.919, respectively. The results showed that the models constructed in this work could provide estimation stability and favorable predictive ability.展开更多
Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. A...Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. As a conjugation specific cyclin gene, CYC2 knockout mutants failed to form an elongated crescent structure and aborted meiosis progress in T. thermophila. γ-H2 A.X staining revealed fewer micronuclear DNA double-strand breaks(DSBs) in cyc2Δ cells than in wild-type cells. Furthermore, cyc2Δ cells still failed to form a crescent structure even though DSBs were induced by exogenous agents,indicating that a lack of DSBs was not completely responsible for failure to enter the crescent stage. Tubulin staining showed that impaired perinuclear microtubule structure may contribute to the blockage in micronuclear elongation. At the same time,expression of microtubule-associated kinesin genes, KIN11 and KIN141, was significantly downregulated in cyc2Δ cells.Moreover, micronuclear specific accumulation of heterochromatin marker trimethylated H3 K23 abnormally increased in the cyc2Δ mutants. Together, these results show that cyclin Cyc2 p is required for micronuclear bouquet formation via controlling microtubule-directed nuclear elongation in Tetrahymena.展开更多
Histone modification and nucleosome assembly play important roles in chromatin-related processes.Histone chaperones form different complexes and coordinate histone transportation and assembly.Various histone chaperone...Histone modification and nucleosome assembly play important roles in chromatin-related processes.Histone chaperones form different complexes and coordinate histone transportation and assembly.Various histone chaperone complexes have been identified in different organisms.The ciliate protozoa(ciliates)have various chromatin structures and different nuclear morphology.However,histone chaperone components and functions of different subunits remain unclear in ciliates.Tet-rahymema thermophila contains a transcriptionally active macronucleus(MAC)and a transcriptionally inactive micronu-cleus(MIC)which exhibit multiple replication and various chromatin remodeling progresses during vegetative growth and sexual developmental stages.Here,we found histone chaperone RebL1 not only localized evenly in the transcriptionally active MAC but also dynamically changed in the MIC during vegetative growth and sexual developmental stages.REBL1 knockdown inhibited cellular proliferation.The macronuclear morphology became bigger in growing mutants.The abnormal macronuclear structure also occurred in the starvation stage.Furthermore,micronuclear meiosis was disturbed during sexual development,leading to a failure to generate new gametic nuclei.RebL1 potentially interacted with various factors involved in histone-modifying complexes and chromatin remodeling complexes in different developmental stages.REBL1 knockdown affected expression levels of the genes involved in chromatin organization and transcription.Taken together,RebL1 plays a vital role in maintaining macronuclear structure stability and gametogenesis in T.thermophila.展开更多
Pyraclostrobin(PYR),a widely used fungicide,has negative effects on fish and algae,but its toxicity in protozoa remains unclear.In this study,the effects of PYR on the growth,oxidative stress,and gene expression relat...Pyraclostrobin(PYR),a widely used fungicide,has negative effects on fish and algae,but its toxicity in protozoa remains unclear.In this study,the effects of PYR on the growth,oxidative stress,and gene expression related to stress and ATP-binding cassette(ABC)transporters in Tetrahymena thermophila were investigated.The result showed that the 96-h IC_(50)of PYR against T.thermophila was 17.2 mg/L.Moreover,PYR inhibited the growth of T.thermophila in concentration-or time-dependent manner.A morphological study revealed that the shape and size of T.thermophila changed,and damage of cell membrane surface was observed by scanning electron microscopy after 96 h of PYR exposure.The activities of superoxide dismutase(SOD)and catalase(CAT)increased throughout the experiment.In contrast,the glutathione(GSH)content was increased at 24 h and 48 h of exposure and decreased at 96 h.Moreover,a significant increase in malondialdehyde(MDA)level was observed in T.thermophila after96 h of exposure.Furthermore,PYR upregulated the HSP703,HSP705,GPx2,and ABAC15 gene expression in the 0.1–5-mg/L groups and downregulated the HSP704,HSP90,TGR,and ABCC52 mRNA levels at 96 h of exposure.These results suggest that PYR may exert adverse effects on T.thermophila by inducing oxidative stress and changing the gene expression related to ABC transporters and stress,which may enrich the understanding of the toxicity mechanism of PYR in aquatic organisms and provide reference data for aquatic ecological risk assessments.展开更多
Tetrahymena thermophila is a model eukaryotic organism. Functional genomic analyses in Tetrahymena present rich opportunities to address fundamental questions of cell and molecular biology. The Tetrahymena Gene Expres...Tetrahymena thermophila is a model eukaryotic organism. Functional genomic analyses in Tetrahymena present rich opportunities to address fundamental questions of cell and molecular biology. The Tetrahymena Gene Expression Database (TGED; available at http://tged.ihb.ac.cn) is the first expression database of a ciliated protozoan. It covers three major physiological and developmental states: growth, starvation, and conjugation, and can be accessed through a user-friendly web interface. The gene expression profiles and candidate co-expressed genes for each gene can be retrieved using Gene ID or Gene description searches. Descriptions of standardized methods of sample preparation and the opportunity to add new Tetrahymena microarray data will be of great interest to the Tetrahymena research community. TGED is intended to be a resource for all members of the scientific research community who are interested in Tetrahymena and other ciliates.展开更多
Genomic distribution of the nucleosome, the basic unit of chromatin, contains important epigenetic information. To map nucleosome distribution in structurally and functionally differentiated micronucleus(MIC) and macr...Genomic distribution of the nucleosome, the basic unit of chromatin, contains important epigenetic information. To map nucleosome distribution in structurally and functionally differentiated micronucleus(MIC) and macronucleus(MAC) of the ciliate Tetrahymena thermophila, we have purified MIC and MAC and performed micrococcal nuclease(MNase) digestion as well as hydroxyl radical cleavage. Different factors that may affect MNase digestion were examined, to optimize mono-nucleosome production. Mono-nucleosome purity was further improved by ultracentrifugation in a sucrose gradient. As MNase concentration increased, nucleosomal DNA sizes in MIC and MAC converged on 147 bp, as expected for the nucleosome core particle. Both MNase digestion and hydroxyl radical cleavage consistently showed a nucleosome repeat length of^200 bp in MAC of Tetrahymena, supporting ~50 bp of linker DNA. Our work has systematically tested methods currently available for mapping nucleosome distribution in Tetrahymena, and provided a solid foundation for future epigenetic studies in this ciliated model organism.展开更多
Epigenetic research focuses on heritable changes beyond the DNA sequence, which has led to a revolution in biologicalstudies and benefits in many other fields. The well-known model ciliate, Tetrahymena thermophila off...Epigenetic research focuses on heritable changes beyond the DNA sequence, which has led to a revolution in biologicalstudies and benefits in many other fields. The well-known model ciliate, Tetrahymena thermophila offers a unique system forepigenetic studies due to its nuclear dimorphism and special mode of sexual reproduction (conjugation), as well as abundantgenomic resources and genetic tools. In this paper, we summarize recent progress made by our research team and collaboratorsin understanding epigenetic mechanisms using Tetrahymena. This includes: (1) providing the first genome-wide basepair-resolution map of DNA N6-methyladenine (6mA) and revealed it as an integral part of the chromatin landscape;(2)dissecting the relative contribution of cis・ and trans- elements to nucleosome distribution by exploring the unique nucleardimorphism of Tetrahymena, (3) demonstrating the epigenetic controls of RNAi-dependent Polycomb repression pathwayson transposable elements, and (4) identifying a new histone monomethyltransferase, TXR1 (Tetrahymena Trithorax 1), thatfacilitates replication elongation through 让s substrate histone H3 lysine 27 monomethylation (H3K27mel).展开更多
The ciliate Tetrahymena thermophila has been a powerful model system for molecular and cellular biology.However,some investigations have been limited due to the incomplete closure and sequencing of the macronuclear ge...The ciliate Tetrahymena thermophila has been a powerful model system for molecular and cellular biology.However,some investigations have been limited due to the incomplete closure and sequencing of the macronuclear genome assembly,which for many years has been stalled at 1,158 scaffolds,with large sections of unknown sequences(available in Tetrahymena Genome Database,TGD,http://ciliate.org/).Here we completed the first chromosome-level Tetrahymena macronuclear genome assembly,with approximately 300×long Single Molecule,Real-Time reads of the wild-type SB210 cells—the reference strain for the initial macronuclear genome sequencing project.All 181 chromosomes were capped with two telomeres and gaps were entirely closed.The completed genome shows significant improvements over the current assembly(TGD 2014)in both chromosome structure and sequence integrity.The majority of previously identified gene models shown in TGD were retained,with the addition of 36 new genes and 883 genes with modified gene models.The new genome and annotation were incorporated into TGD.This new genome allows for pursuit in some underexplored areas that were far more challenging previously;two of them,genome scrambling and chromosomal copy number,were investigated in this study.We expect that the completed macronuclear genome will facilitate many studies in Tetrahymena biology,as well as multiple lines of research in other eukaryotes.展开更多
Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a hig...Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a highly specialized zipper-like protein complex,the synaptonemal complex(SC),to guide and stabilize pairing of homologous chromosomes in meiosis.Although the SC is critical for meiosis in many eukaryotes,there are organisms that perform meiosis without a functional SC.However,such SC-less meiosis is poorly characterized.To understand the features of SC-less meiosis and its adaptive significance,the ciliated protozoan Tetrahymena was selected as a model.Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis,yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC.Here,aiming at promoting a wider application of Tetrahymena for meiosis research,we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox.These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features.Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective.展开更多
Norfloxacin complexes Co（nor）2.8H2O （nor=norfloxaein） and [Co（nor）（phen）]NO3.2H2O （phen=1,10-phenanthroline） were synthesized and their biological activity on Tetrahymena and Escherichia coli （E.coli） was ...Norfloxacin complexes Co（nor）2.8H2O （nor=norfloxaein） and [Co（nor）（phen）]NO3.2H2O （phen=1,10-phenanthroline） were synthesized and their biological activity on Tetrahymena and Escherichia coli （E.coli） was assayed by means of microcalorimetry. Massive experimental parameters such as the growth constant k, inhibitory ratio I, half inhibition concentration IC5o and generation time TG were obtained. Data showed that with the increase of exposing complex concentration, both complexes exhibited strong inhibition during the growth of organisms. While toxic degrees were quite different on Tetrahymena and E.coli, due to various toxic mechanisms. And complex molecular volume and the ability of the complex penetrating into cells may be the keys.展开更多
基金support by the Natural Science Foundation of University, Anhui Province (No. 2006KJ156B)
文摘Structural parameters of 22 halogen phenols were computed at four levels using Hartree-Fock and DFT methods. Based on the experimental data of the acute toxicity to Tetrahymena pyriformis （-lgEC_50）, three-parameter （energy of the lowest unoccupied molecular orbital （E_LUMO）, the molecular volume （V）, and the lowest negative charge （Q_min）） dependent equations were developed using structural parameters as theoretical descriptors. Especially, -lgEC_50dependent equation calculated at the B3LYP/6-31G^＊＊ level is more advantageous than the others in view of their correlation and predictive abilities. This dependent equation was validated by variance inflation factors （VIF） and t-test methods. Upon comparison, the predictive abilities of our work are all more advantageous than those calculated from the semi-empirical PM3 method.
基金Supported by the Educational Ministry Foundation of China(No. 0 10 6 3) .Tetrahymena pyriformis B was kindlysupplied by Dr.TiedkeMünster
文摘The IGC 50 (50% inhibitory growth concentration) values of 27 nitrobenzenes were determined for the population growth endpoint of Tetrahymena pyriformis . The toxicity order of the observed compounds was found to be as follows: dinitro compounds>mononitro compounds, dichloronitrobenzenes>monochloronitrobenzenes, meta substituted nitrobenzenes>ortho /para substituted nitrobenzenes(NT, NPh, NAnis) except for the dinitrobenzenes and nitroanilines(DNB, NAn). Quantitative structure activity relationships(QSARs) were developed with the logarithm of the reciprocal of IGC 50 [lg(IGC 50 ) -1 ] in mole liter as dependent variable and six molecular descriptors lg P , 1 X Ⅴ, I, 1K a, ∑σ - and E LUMO as independent variables. Via multiple regression analysis, one best equation was obtained: lg(IGC 50 ) -1 =3.029+0.860∑ σ -+0.341I n=27, r=0.924, r 2=0.854, s=0.265, f=70.44 , Pr> f =0.000 1 The equation was used to estimate IGC 50 for five analogues.
文摘Autophagy is a major cellular pathway used to degrade long-lived proteins or organelles that may be damaged due to increased reactive oxygen species（ROS） generated by cellular stress. Autophagy typically enhances cell survival, but it may also act to promote cell death under certain conditions. The mechanism underlying this paradox, however, remains unclear. We showed that Tetrahymena cells exerted increased membranebound vacuoles characteristic of autophagy followed by autophagic cell death（referred to as cell death with autophagy） after exposure to hydrogen peroxide. Inhibition of autophagy by chloroquine or 3-methyladenine significantly augmented autophagic cell death induced by hydrogen peroxide. Blockage of the mitochondrial electron transport chain or starvation triggered activation of autophagy followed by cell death by inducing the production of ROS due to the loss of mitochondrial membrane potential. This indicated a regulatory role of mitochondrial ROS in programming autophagy and autophagic cell death in Tetrahymena. Importantly, suppression of autophagy enhanced autophagic cell death in Tetrahymena in response to elevated ROS production from starvation, and this was reversed by antioxidants. Therefore, our results suggest that autophagy was activated upon oxidative stress to prevent the initiation of autophagic cell death in Tetrahymena until the accumulation of ROS passed the point of no return, leading to delayed cell death in Tetrahymena.
基金State Natural Science Foundation(81173571)The"Twelfth Five-Year Plan"Foundation of China People’s Liberation Army(CWS11C164)The Major Projects of the National Science and Technology(2012ZX10005010-002-002)
文摘Objective To explore the active components with toxic effects in five Aconitum L. herbal medicines on Tetrahymena thermophila. Methods The fingerprints of five Aconitum L. herbal medicines were established by ultra-high performance liquid chromatography （UPLC） and the toxicity was evaluated by using a TAM Air Isothermal Calorimeter on Tetrahymena thermophila SB1 10. Results By analyzing the spectrum- effect relationships between UPLC fingerprints and toxic effects, the active components which had the toxic effects were obtained. Conclusion This work provides a general model of the combination of UPLC and microcalorimetry to study the spectrum-effect relationships of the five Aconitum L. herbal medicines, which could be used to evaluate the toxic effects and analyze the principal toxic components of the five Aconitum L. herbal medicines. On the whole, this result provides the experimental basis for the safe use of the five Aconitum L. herbal medicines in clinic.
基金Project supported by the National Natural Science Foundation of China （Nos. 39970911 and 30371724）.
文摘The growth therrnogenic curves of Staphylococcus aureus and Tetrahymena thermophila affected by 1,8-dihydroxyanthraquinone, emodin and rhein were determined quantitatively by microcalorimetry. The inhibitory effects of the three anthraquinones （AQ） on S. aureus revealed that the sequence of antimicrobial activity of those was rhein〉emodin〉 1,8-dihydroxyanthraquinone. The toxicity of the three AQ on T. thermophila indicated that all the tested AQ were toxic to the tested protozoa and the hydroxyl and carboxyl substituted at different position of anthraquinone ring resulted in the enhancement of toxicity.
基金supported by the Youth Foundation of Education Bureau, Sichuan Province (09ZB036)Technology Bureau, Sichuan Province (2006j13-141)
文摘The molecular electronegativity interaction vector （MEIV） was used to describe the molecular structure of 30 selected esters. Two excellent QSTR models were built up by using multiple linear regression （MLR） and partial least-squares regression （PLS）. The correlation coefficients （R） of the two models were 0.945 and 0.941, respectively. The models were evaluated by performing the cross validation with the leave-one-out （LOO） procedure. The cross-verification correlation coefficients （RCV） of the two models were 0.921 and 0.919, respectively. The results showed that the models constructed in this work could provide estimation stability and favorable predictive ability.
基金supported by the National Natural Science Foundation of China(31471999,31572253)Shanxi Scholarship Council of China(200902)+2 种基金Aoshan Science and Technology Innovation Program of the Qingdao National Laboratory for Marine Science and Technologythe China Postdoctoral Science Foundation(2014M551961)the Natural Science Foundation of Shanxi Province(2015011078)
文摘Meiotic bouquet formation(known as crescent formation in Tetrahymena thermophila) is indispensable for homologous pairing and recombination, but the regulatory mechanism of bouquet formation remains largely unknown. As a conjugation specific cyclin gene, CYC2 knockout mutants failed to form an elongated crescent structure and aborted meiosis progress in T. thermophila. γ-H2 A.X staining revealed fewer micronuclear DNA double-strand breaks(DSBs) in cyc2Δ cells than in wild-type cells. Furthermore, cyc2Δ cells still failed to form a crescent structure even though DSBs were induced by exogenous agents,indicating that a lack of DSBs was not completely responsible for failure to enter the crescent stage. Tubulin staining showed that impaired perinuclear microtubule structure may contribute to the blockage in micronuclear elongation. At the same time,expression of microtubule-associated kinesin genes, KIN11 and KIN141, was significantly downregulated in cyc2Δ cells.Moreover, micronuclear specific accumulation of heterochromatin marker trimethylated H3 K23 abnormally increased in the cyc2Δ mutants. Together, these results show that cyclin Cyc2 p is required for micronuclear bouquet formation via controlling microtubule-directed nuclear elongation in Tetrahymena.
基金supported by the National Natural Science Foundation of China(32270450,32071449)Shanxi Key Program International S&T Cooperation Projects(202104041101011)Shanxi Scholarship Council of China(2020016).
文摘Histone modification and nucleosome assembly play important roles in chromatin-related processes.Histone chaperones form different complexes and coordinate histone transportation and assembly.Various histone chaperone complexes have been identified in different organisms.The ciliate protozoa(ciliates)have various chromatin structures and different nuclear morphology.However,histone chaperone components and functions of different subunits remain unclear in ciliates.Tet-rahymema thermophila contains a transcriptionally active macronucleus(MAC)and a transcriptionally inactive micronu-cleus(MIC)which exhibit multiple replication and various chromatin remodeling progresses during vegetative growth and sexual developmental stages.Here,we found histone chaperone RebL1 not only localized evenly in the transcriptionally active MAC but also dynamically changed in the MIC during vegetative growth and sexual developmental stages.REBL1 knockdown inhibited cellular proliferation.The macronuclear morphology became bigger in growing mutants.The abnormal macronuclear structure also occurred in the starvation stage.Furthermore,micronuclear meiosis was disturbed during sexual development,leading to a failure to generate new gametic nuclei.RebL1 potentially interacted with various factors involved in histone-modifying complexes and chromatin remodeling complexes in different developmental stages.REBL1 knockdown affected expression levels of the genes involved in chromatin organization and transcription.Taken together,RebL1 plays a vital role in maintaining macronuclear structure stability and gametogenesis in T.thermophila.
基金the Key Scientific Research Projects of Henan Province to College Youth Backbone Teacher(No.2021118)the National Key Research and Development Program of China(No.2021YFE0112000)。
文摘Pyraclostrobin(PYR),a widely used fungicide,has negative effects on fish and algae,but its toxicity in protozoa remains unclear.In this study,the effects of PYR on the growth,oxidative stress,and gene expression related to stress and ATP-binding cassette(ABC)transporters in Tetrahymena thermophila were investigated.The result showed that the 96-h IC_(50)of PYR against T.thermophila was 17.2 mg/L.Moreover,PYR inhibited the growth of T.thermophila in concentration-or time-dependent manner.A morphological study revealed that the shape and size of T.thermophila changed,and damage of cell membrane surface was observed by scanning electron microscopy after 96 h of PYR exposure.The activities of superoxide dismutase(SOD)and catalase(CAT)increased throughout the experiment.In contrast,the glutathione(GSH)content was increased at 24 h and 48 h of exposure and decreased at 96 h.Moreover,a significant increase in malondialdehyde(MDA)level was observed in T.thermophila after96 h of exposure.Furthermore,PYR upregulated the HSP703,HSP705,GPx2,and ABAC15 gene expression in the 0.1–5-mg/L groups and downregulated the HSP704,HSP90,TGR,and ABCC52 mRNA levels at 96 h of exposure.These results suggest that PYR may exert adverse effects on T.thermophila by inducing oxidative stress and changing the gene expression related to ABC transporters and stress,which may enrich the understanding of the toxicity mechanism of PYR in aquatic organisms and provide reference data for aquatic ecological risk assessments.
基金supported by the National Natural Science Foundation of China (Grant Nos. 30870356 and 30970424)the Knowledge Innovation Program of Chinese Academy of Sciences (Grant No. KSCX2-YW-G-072)the National Institutes of Health (Grant Nos. GM021793 and GM072752)
文摘Tetrahymena thermophila is a model eukaryotic organism. Functional genomic analyses in Tetrahymena present rich opportunities to address fundamental questions of cell and molecular biology. The Tetrahymena Gene Expression Database (TGED; available at http://tged.ihb.ac.cn) is the first expression database of a ciliated protozoan. It covers three major physiological and developmental states: growth, starvation, and conjugation, and can be accessed through a user-friendly web interface. The gene expression profiles and candidate co-expressed genes for each gene can be retrieved using Gene ID or Gene description searches. Descriptions of standardized methods of sample preparation and the opportunity to add new Tetrahymena microarray data will be of great interest to the Tetrahymena research community. TGED is intended to be a resource for all members of the scientific research community who are interested in Tetrahymena and other ciliates.
基金supported by the Natural Science Foundation of China(31522051,31470064)the funding awarded to Weibo Song(15-12-1-1-jch)+3 种基金the Qingdao National Laboratory for Marine Science and Technology,ChinaYifan Liu was supported by National Sanitation Foundation(MCB 1411565)National Institute of Health(R01 GM087343)the Department of Pathology at the University of Michigan
文摘Genomic distribution of the nucleosome, the basic unit of chromatin, contains important epigenetic information. To map nucleosome distribution in structurally and functionally differentiated micronucleus(MIC) and macronucleus(MAC) of the ciliate Tetrahymena thermophila, we have purified MIC and MAC and performed micrococcal nuclease(MNase) digestion as well as hydroxyl radical cleavage. Different factors that may affect MNase digestion were examined, to optimize mono-nucleosome production. Mono-nucleosome purity was further improved by ultracentrifugation in a sucrose gradient. As MNase concentration increased, nucleosomal DNA sizes in MIC and MAC converged on 147 bp, as expected for the nucleosome core particle. Both MNase digestion and hydroxyl radical cleavage consistently showed a nucleosome repeat length of^200 bp in MAC of Tetrahymena, supporting ~50 bp of linker DNA. Our work has systematically tested methods currently available for mapping nucleosome distribution in Tetrahymena, and provided a solid foundation for future epigenetic studies in this ciliated model organism.
基金supported by Natural Science Foundation ofShandong Province (JQ201706)The Marine S&T Fund of ShandongProvince for Pilot National Laboratory for Marine Science and Technology(Qingdao) (2018SDKJ0406-2)+1 种基金Fundamental Research Fundsfor the Central Universities (201841005)the Blue Life BreakthroughProgram of LMBB of Qingdao National Laboratory for MarineScience and Technology (MS2018N004).
文摘Epigenetic research focuses on heritable changes beyond the DNA sequence, which has led to a revolution in biologicalstudies and benefits in many other fields. The well-known model ciliate, Tetrahymena thermophila offers a unique system forepigenetic studies due to its nuclear dimorphism and special mode of sexual reproduction (conjugation), as well as abundantgenomic resources and genetic tools. In this paper, we summarize recent progress made by our research team and collaboratorsin understanding epigenetic mechanisms using Tetrahymena. This includes: (1) providing the first genome-wide basepair-resolution map of DNA N6-methyladenine (6mA) and revealed it as an integral part of the chromatin landscape;(2)dissecting the relative contribution of cis・ and trans- elements to nucleosome distribution by exploring the unique nucleardimorphism of Tetrahymena, (3) demonstrating the epigenetic controls of RNAi-dependent Polycomb repression pathwayson transposable elements, and (4) identifying a new histone monomethyltransferase, TXR1 (Tetrahymena Trithorax 1), thatfacilitates replication elongation through 让s substrate histone H3 lysine 27 monomethylation (H3K27mel).
基金Supported by the Natural Science Foundation of Shandong Province (JQ201706)The Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology (Qingdao) (2018SDKJ0406-2)+2 种基金Fundamental Research Funds for the Central Universities (201841005)the Blue Life Breakthrough Program of LMBB of Qingdao National Laboratory for Marine Science and Technology (MS2018NO04)and National Institutes of Health (2P40OD010964).
文摘The ciliate Tetrahymena thermophila has been a powerful model system for molecular and cellular biology.However,some investigations have been limited due to the incomplete closure and sequencing of the macronuclear genome assembly,which for many years has been stalled at 1,158 scaffolds,with large sections of unknown sequences(available in Tetrahymena Genome Database,TGD,http://ciliate.org/).Here we completed the first chromosome-level Tetrahymena macronuclear genome assembly,with approximately 300×long Single Molecule,Real-Time reads of the wild-type SB210 cells—the reference strain for the initial macronuclear genome sequencing project.All 181 chromosomes were capped with two telomeres and gaps were entirely closed.The completed genome shows significant improvements over the current assembly(TGD 2014)in both chromosome structure and sequence integrity.The majority of previously identified gene models shown in TGD were retained,with the addition of 36 new genes and 883 genes with modified gene models.The new genome and annotation were incorporated into TGD.This new genome allows for pursuit in some underexplored areas that were far more challenging previously;two of them,genome scrambling and chromosomal copy number,were investigated in this study.We expect that the completed macronuclear genome will facilitate many studies in Tetrahymena biology,as well as multiple lines of research in other eukaryotes.
基金Funds for the Central Universities(No.202241003,to Dr.Miao Tian)the Natural Science Foundation of Shandong Province(ZR2022JQ13,to Dr.Miao Tian)+1 种基金by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement(No.101024333)Dr.Rachel Howard-Till is supported by NIH RO1GM127571.
文摘Meiosis is a critical cell division program that produces haploid gametes for sexual reproduction.Abnormalities in meiosis are often causes of infertility and birth defects(e.g.,Down syndrome).Most organisms use a highly specialized zipper-like protein complex,the synaptonemal complex(SC),to guide and stabilize pairing of homologous chromosomes in meiosis.Although the SC is critical for meiosis in many eukaryotes,there are organisms that perform meiosis without a functional SC.However,such SC-less meiosis is poorly characterized.To understand the features of SC-less meiosis and its adaptive significance,the ciliated protozoan Tetrahymena was selected as a model.Meiosis research in Tetrahymena has revealed intriguing aspects of the regulatory programs utilized in its SC-less meiosis,yet additional efforts are needed for obtaining an in-depth comprehension of mechanisms that are associated with the absence of SC.Here,aiming at promoting a wider application of Tetrahymena for meiosis research,we introduce basic concepts and core techniques for studying meiosis in Tetrahymena and then suggest future directions for expanding the current Tetrahymena meiosis research toolbox.These methodologies could be adopted for dissecting meiosis in poorly characterized ciliates that might reveal novel features.Such data will hopefully provide insights into the function of the SC and the evolution of meiosis from a unique perspective.
基金Funded by the National Natural Science Foundation of China(No.51273155)the Fundamental Research Funds for the Central Universities(No.2012-Ia-022)
文摘Norfloxacin complexes Co（nor）2.8H2O （nor=norfloxaein） and [Co（nor）（phen）]NO3.2H2O （phen=1,10-phenanthroline） were synthesized and their biological activity on Tetrahymena and Escherichia coli （E.coli） was assayed by means of microcalorimetry. Massive experimental parameters such as the growth constant k, inhibitory ratio I, half inhibition concentration IC5o and generation time TG were obtained. Data showed that with the increase of exposing complex concentration, both complexes exhibited strong inhibition during the growth of organisms. While toxic degrees were quite different on Tetrahymena and E.coli, due to various toxic mechanisms. And complex molecular volume and the ability of the complex penetrating into cells may be the keys.
