After the third prezygotic division during conjugation of Paramecium caudatum,migratory and stationary pronuclei are produced.The migratory pronuclei remain in the paroral region tightly against the conjugating bounda...After the third prezygotic division during conjugation of Paramecium caudatum,migratory and stationary pronuclei are produced.The migratory pronuclei remain in the paroral region tightly against the conjugating boundaries;while the stationary pronuclei are located beside the migratory pronuclei.To date,however,it is not clear what causes this close side-by-side localization between migratory and stationary pronuclei.In the current study,immunofluorescence staining with monoclonal antibody of anti-α tubulin indicated that ＂U＂ or ＂V＂ shaped spindles connected the migratory and stationary pronuclei during the third prezygotic division.This observation accounts for the close localization between these two types of pronuclei.展开更多
The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in...The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x–9.51 (R2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h–LC50 value for ammonia was found to be 95.50 mg/L. A linear correla- tion between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equa- tion y=2.86x+0.89 (R2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 value and ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.展开更多
Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no v...Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no validated model to assess the presumed candidate sites of the anesthetics. We undertook this study to test the hypothesis that the single-celled Paramecium could be anesthetized and served as a model organism in the study of anesthetics. We assessed the motion of Paramecium cells with Expert Vision system and the chemoresponse of Paramecium cells with T-maze assays in the presence of four different volatile anesthetics, including isoflurane, sevoflurane, enflurane and ether. Each of those volatiles was dissolved in buffers to give drug concentrations equal to 0.8, 1.0, and 1.2 EC50, respectively, in clinical practice. We could see that after application of volatile anesthetics, the swimming of the Paramecium cells was accelerated and then suppressed, or even stopped eventually, and the index of the chemoresponse of the Paramecium cells （denoted as Iche） was decreased. All of the above impacts were found in a concentration-dependent fashion. The biphasic effects of the clinical concentrations of volatile anesthetics on Paramecium simulated the situation of high species in anesthesia, and the inhibition of the chemoresponse also indicated anesthetized. In conclusion, the findings in our studies suggested that the single-celled Paramecium could be anesthetized with clinical concentrations of volatile anesthetics and therefore be utilized as a model organism to study the mechanisms of volatile anesthetics.展开更多
<span style="font-family:Verdana;">A simple method for assessment of the toxicity and antidote effect of selenium nanoparticles with </span><i><i><span style="font-family:Verd...<span style="font-family:Verdana;">A simple method for assessment of the toxicity and antidote effect of selenium nanoparticles with </span><i><i><span style="font-family:Verdana;">Paramecium</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i><span style="font-family:Verdana;"> is presented. Light microscopy in combination with computerized video tracking is employed for </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">determination of </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">survival time of <i></i></span><i><i><span style="font-family:Verdana;">P.</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;">. Up to 800 mg/L, selenium nanoparticles are not acutely toxic. </span><span style="font-family:Verdana;">With</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> respect to a potential antidote effect, the lethality of silver nanoparticles, silver nitrate, sodium hydrogen selenite, and sodium selenite to <i></i></span><i><i><span style="font-family:Verdana;">P.</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;"> was decreased and survival time was extend</span><span style="font-family:Verdana;">ed upon pre-treatment with selenium nanoparticles. Taken together, these findings suggest that administration of selenium nanoparticles attenuates</span><span style="font-family:Verdana;"> exposure </span><span style="font-family:Verdana;">to</span><span style="font-family:Verdana;"> toxicants. Selenium nanoparticles could be a good functional additive for food management in animals.</span>展开更多
There are six micronuclear divisions during conjugation of Paramecium caudatum:three prezygotic and three postzygotic divisions.Four haploid nuclei are formed during the first two meiotic prezygotic divisions.Usually ...There are six micronuclear divisions during conjugation of Paramecium caudatum:three prezygotic and three postzygotic divisions.Four haploid nuclei are formed during the first two meiotic prezygotic divisions.Usually only one meiotic product is located in the paroral cone(PC)region at the completion of meiosis,which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus.The remaining three located outside of the PC degenerate.The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya,which undergo three successive divisions(postzygotic divisions).However,little is known about the surviving mechanism of the PC nuclei.In the current study,stage-specific appearance of cytoplasmic microtubules(cMTs)was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei,including the PC nuclei and the two types of prospective pronuclei.This suggested that cMTs were involved in the formation of a physical barrier,whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm,where degeneration of extra-meiotic products occurs,another important nuclear event during the third prezygotic division.展开更多
There are six micronuclear divisions during conjugation of Paramecium caudatum： three prezygotic and three postzygotic divisions. Four haploid nuclei are formed during the first two meiotic prezygotic divisions. Usua...There are six micronuclear divisions during conjugation of Paramecium caudatum： three prezygotic and three postzygotic divisions. Four haploid nuclei are formed during the first two meiotic prezygotic divisions. Usually only one meiotic product is located in the paroral cone （PC） region at the completion of meiosis, which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus. The remaining three located outside of the PC degenerate. The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya, which undergo three successive divisions （postzygotic divisions）. However, little is known about the surviving mechanism of the PC nuclei. In the current study, stage-specific appearance of cytoplasmic microtubules （cMTs） was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei, including the PC nuclei and the two types of prospective pronuclei. This suggested that cMTs were involved in the formation of a physical barrier, whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm, where degeneration of extra-meiotic products occurs, another important nuclear event during the third prezygotic division.展开更多
The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each...The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each P. bursaria strain. In most cases, the algal partners are restricted to either Chlorella variabilis or Micractinium reisseri (Chlorellaceae, Trebouxiophyceae). Both species are characterized by particular physiology and atypical group I intron insertions, although they are morphologically indistinguishable from each other or from other Chlorella-related species. Both algae are exclusive species that are viable only within P. bursaria cells, and therefore their symbiotic relationship can be considered persistent. In a few cases, the other algal species have been reported as P. bursaria photobionts. Namely, P. bursaria have occasionally replaced their photobiont partner. This paper introduces some P. bursaria strains that maintain more than one species of algae for a long period. This situation prompts speculations about flexibility of host-photo-biont relationships, how P. bursaria replaced these photobionts, and the infection theory of the group I introns.展开更多
During conjugation of Paramecium caudatum,nuclear events occur in a scheduled program.Morphological studies on nuclear behavior during conjugation of P.caudatum have been performed since the end of the 19th century.He...During conjugation of Paramecium caudatum,nuclear events occur in a scheduled program.Morphological studies on nuclear behavior during conjugation of P.caudatum have been performed since the end of the 19th century.Here we report on new details concerning the conjugation of P.caudatum through the staining of conjugating ceils with protargol,carbol fuchsin solution,Hoechst 33342 and immunofluorescence labeling with monoclonal antibody of anti-a tubulin.1)The crescent nucleus is a characteristic of the meiotic prophase of P.caudatum,has an unstained area.We stained this area with protargol,which was separated from the chromatin area and was not detected by the other stainings.2)In regards to the four meiotic products,it has long been considered that only one product enters the paroral cone region(PC)and survives after meiosis.However,our protargol and immunofluorescence labeling results indicated that PC entrance of the meiotic product happened before the completion of meiosis instead of after.3)In our previous study,protargol staining indicated the presence of a swollen structure around the central part of the"U"and"V"shaped spindles connecting the two types of prospective pronuclei.However,immunofluorescence labeling with anti-a tubulin antibodies gave a different image from protargol.All these observations form the basis for further studies of their molecular mechanisms.展开更多
Paramecium,a group of ciliates with a long evolutionary history,plays essential roles in freshwater ecosystems and has been model for genetic,cellular,and evolutionary studies for over a century.Despite the valuable c...Paramecium,a group of ciliates with a long evolutionary history,plays essential roles in freshwater ecosystems and has been model for genetic,cellular,and evolutionary studies for over a century.Despite the valuable contributions of genomic resources such as ParameciumDB,genomic data are still mostly limited to species in and near the P.aurelia group.This study addresses this gap by HiFi sequencing,assembling,and annotating the macronuclear genomes of five rare Paramecium species:P.calkinsi,P.duboscqui,P.nephridiatum,P.putrinum,and P.woodruffi.These genomes enable a comprehensive exploration of genomic diversity,genome evolution,and phylogenomic relationships within the genus Paramecium.The genome sizes range from 47.78 to 113.16 Mb,reflecting unexpected variation in genomic content,and genic features differ from those of other reported Paramecium genomes,such as larger intron sizes and higher GC content.Nonetheless,the de novo assemblies indicate that macronuclear genomes of all Paramecium are highly streamlined,with~77%being protein-coding gene regions.Based on gene-duplication depths,synonymous mutations in paralogs,and phylogenomic relationships,we discovered that the five species experienced at least three whole-genome duplication(WGD)events,independent of those previously found in the P.aurelia complex.Using all available WGD data for Paramecium,we further explore the paralog dynamics after WGD events by modeling.This study contributed to a more comprehensive and deeper understanding of genome architecture and evolution in Paramecium.展开更多
Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes(conjugation and autogamy)that rely on their unique nuclear dimorphism,i.e.,the presence of both a germline micro...Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes(conjugation and autogamy)that rely on their unique nuclear dimorphism,i.e.,the presence of both a germline micronucleus(MIC)and a somatic macronucleus(MAC)in a single cell.The sexual processes show a high diversity in different ciliates.To better understand the differentiation and evolution of sexual processes in closely related species,we investigated the nuclear events during conjugation in Paramecium jenningsi strain GZ,a poorly studied close relative of the well-known P.aurelia complex.The main results include:(1)the conjugation process takes about 48 h,including three prezygotic divisions(meiosis I,II,and mitosis)and three postzygotic divisions;(2)the MICs are dominated by the“parachute”phase at the prophase of meiosis I;(3)after meiosis II,a variable number of nuclei undergo the third prezygotic division,and the two products near the paroral cone become the genetically identical migratory and stationary pronuclei;(4)the synkaryon divides three times to form the MIC and the MAC anlagen,but only one nuclear product of the first postzygotic division completes the next two divisions;and(5)an extra cell division is required to complete the last step of conjugation,during which two MIC anlagen undergo mitotic division while two MAC anlagen are distributed between the daughter cells without division.The comparison of the nuclear events during conjugation in representatives of the class Oligohymenophorea reveals that usually there are three prezygotic divisions and a variable number of postzygotic divisions.However,the number of selected and differentiated nuclei after each division differs among species.This study provided a new model ciliate for further investigations of nuclear selection and differentiation as well as nuclear morphology during meiosis.展开更多
文摘After the third prezygotic division during conjugation of Paramecium caudatum,migratory and stationary pronuclei are produced.The migratory pronuclei remain in the paroral region tightly against the conjugating boundaries;while the stationary pronuclei are located beside the migratory pronuclei.To date,however,it is not clear what causes this close side-by-side localization between migratory and stationary pronuclei.In the current study,immunofluorescence staining with monoclonal antibody of anti-α tubulin indicated that ＂U＂ or ＂V＂ shaped spindles connected the migratory and stationary pronuclei during the third prezygotic division.This observation accounts for the close localization between these two types of pronuclei.
文摘The tolerance to ammonia and nitrites in freshwater ciliate Paramecium bursaria was measured in a conventional open system. The ciliate was exposed to different concentrations of ammonia and nitrites for 2h and 12h in order to determine the lethal concentrations. Linear regression analysis revealed that the 2h-LC50 value for ammonia was 95.94 mg/L and for nitrite 27.35 mg/L using probit scale method (with 95% confidence intervals). There was a linear correlation between the mortality probit scale and logarithmic concentration of ammonia which fit by a regression equation y=7.32x–9.51 (R2=0.98; y, mortality probit scale; x, logarithmic concentration of ammonia), by which 2 h–LC50 value for ammonia was found to be 95.50 mg/L. A linear correla- tion between mortality probit scales and logarithmic concentration of nitrite is also followed the regression equa- tion y=2.86x+0.89 (R2=0.95; y, mortality probit scale; x, logarithmic concentration of nitrite). The regression analysis of toxicity curves showed that the linear correlation between exposed time of ammonia-N LC50 value and ammonia-N LC50 value followed the regression equation y=2 862.85e-0.08x (R2=0.95; y, duration of exposure to LC50 value; x, LC50 value), and that between exposed time of nitrite-N LC50 value and nitrite-N LC50 value followed the regression equation y = 127.15e-0.13x (R2=0.91; y, exposed time of LC50 value; x, LC50 value). The results demonstrate that the tolerance to ammonia in P. bursaria is considerably higher than that of the larvae or juveniles of some metozoa, e.g. cultured prawns and oysters. In addition, ciliates, as bacterial predators, are likely to play a positive role in maintaining and improving water quality in aquatic environments with high-level ammonium, such as sewage treatment systems.
基金supported by a grant from the National Natural Science Foundation of China(No.30972837)
文摘Although empirically well understood in their clinical administration, volatile anesthetics are not yet well comprehended in their mechanism studies. A major conundrum emerging from these studies is that there is no validated model to assess the presumed candidate sites of the anesthetics. We undertook this study to test the hypothesis that the single-celled Paramecium could be anesthetized and served as a model organism in the study of anesthetics. We assessed the motion of Paramecium cells with Expert Vision system and the chemoresponse of Paramecium cells with T-maze assays in the presence of four different volatile anesthetics, including isoflurane, sevoflurane, enflurane and ether. Each of those volatiles was dissolved in buffers to give drug concentrations equal to 0.8, 1.0, and 1.2 EC50, respectively, in clinical practice. We could see that after application of volatile anesthetics, the swimming of the Paramecium cells was accelerated and then suppressed, or even stopped eventually, and the index of the chemoresponse of the Paramecium cells （denoted as Iche） was decreased. All of the above impacts were found in a concentration-dependent fashion. The biphasic effects of the clinical concentrations of volatile anesthetics on Paramecium simulated the situation of high species in anesthesia, and the inhibition of the chemoresponse also indicated anesthetized. In conclusion, the findings in our studies suggested that the single-celled Paramecium could be anesthetized with clinical concentrations of volatile anesthetics and therefore be utilized as a model organism to study the mechanisms of volatile anesthetics.
文摘<span style="font-family:Verdana;">A simple method for assessment of the toxicity and antidote effect of selenium nanoparticles with </span><i><i><span style="font-family:Verdana;">Paramecium</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i><span style="font-family:Verdana;"> is presented. Light microscopy in combination with computerized video tracking is employed for </span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">determination of </span><span style="font-family:Verdana;">the </span><span style="font-family:;" "=""><span style="font-family:Verdana;">survival time of <i></i></span><i><i><span style="font-family:Verdana;">P.</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;">. Up to 800 mg/L, selenium nanoparticles are not acutely toxic. </span><span style="font-family:Verdana;">With</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> respect to a potential antidote effect, the lethality of silver nanoparticles, silver nitrate, sodium hydrogen selenite, and sodium selenite to <i></i></span><i><i><span style="font-family:Verdana;">P.</span></i><span> <i><span style="font-family:Verdana;">caudatum</span></i><span style="font-family:Verdana;"></span></span></i></span><span style="font-family:Verdana;"> was decreased and survival time was extend</span><span style="font-family:Verdana;">ed upon pre-treatment with selenium nanoparticles. Taken together, these findings suggest that administration of selenium nanoparticles attenuates</span><span style="font-family:Verdana;"> exposure </span><span style="font-family:Verdana;">to</span><span style="font-family:Verdana;"> toxicants. Selenium nanoparticles could be a good functional additive for food management in animals.</span>
基金National Natural Science Foundation of China(31071881)Research Development Foundation of Zhejiang A&F University(2009FK67).
文摘There are six micronuclear divisions during conjugation of Paramecium caudatum:three prezygotic and three postzygotic divisions.Four haploid nuclei are formed during the first two meiotic prezygotic divisions.Usually only one meiotic product is located in the paroral cone(PC)region at the completion of meiosis,which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus.The remaining three located outside of the PC degenerate.The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya,which undergo three successive divisions(postzygotic divisions).However,little is known about the surviving mechanism of the PC nuclei.In the current study,stage-specific appearance of cytoplasmic microtubules(cMTs)was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei,including the PC nuclei and the two types of prospective pronuclei.This suggested that cMTs were involved in the formation of a physical barrier,whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm,where degeneration of extra-meiotic products occurs,another important nuclear event during the third prezygotic division.
基金Foundation items： National Natural Science Foundation of China （31071881） Research Development Foundation of Zhejiang A ＆ F University （2009FK67）.
文摘There are six micronuclear divisions during conjugation of Paramecium caudatum： three prezygotic and three postzygotic divisions. Four haploid nuclei are formed during the first two meiotic prezygotic divisions. Usually only one meiotic product is located in the paroral cone （PC） region at the completion of meiosis, which survives and divides mitotically to complete the third prezygotic division to yield a stationary and a migratory pronucleus. The remaining three located outside of the PC degenerate. The migratory pronuclei are then exchanged between two conjugants and fuse with the stationary pronuclei to form synkarya, which undergo three successive divisions （postzygotic divisions）. However, little is known about the surviving mechanism of the PC nuclei. In the current study, stage-specific appearance of cytoplasmic microtubules （cMTs） was indicated during the third prezygotic division by immunofluorescence labeling with anti-alpha tubulin antibodies surrounding the surviving nuclei, including the PC nuclei and the two types of prospective pronuclei. This suggested that cMTs were involved in the formation of a physical barrier, whose function may relate to sequestering and protecting the surviving nuclei from the major cytoplasm, where degeneration of extra-meiotic products occurs, another important nuclear event during the third prezygotic division.
文摘The green ciliate, Paramecium bursaria, has evolved a mutualistic relationship with endosymbiotic green algae (photobionts). Under culture conditions, photobionts are usually unified (to be single species) within each P. bursaria strain. In most cases, the algal partners are restricted to either Chlorella variabilis or Micractinium reisseri (Chlorellaceae, Trebouxiophyceae). Both species are characterized by particular physiology and atypical group I intron insertions, although they are morphologically indistinguishable from each other or from other Chlorella-related species. Both algae are exclusive species that are viable only within P. bursaria cells, and therefore their symbiotic relationship can be considered persistent. In a few cases, the other algal species have been reported as P. bursaria photobionts. Namely, P. bursaria have occasionally replaced their photobiont partner. This paper introduces some P. bursaria strains that maintain more than one species of algae for a long period. This situation prompts speculations about flexibility of host-photo-biont relationships, how P. bursaria replaced these photobionts, and the infection theory of the group I introns.
文摘During conjugation of Paramecium caudatum,nuclear events occur in a scheduled program.Morphological studies on nuclear behavior during conjugation of P.caudatum have been performed since the end of the 19th century.Here we report on new details concerning the conjugation of P.caudatum through the staining of conjugating ceils with protargol,carbol fuchsin solution,Hoechst 33342 and immunofluorescence labeling with monoclonal antibody of anti-a tubulin.1)The crescent nucleus is a characteristic of the meiotic prophase of P.caudatum,has an unstained area.We stained this area with protargol,which was separated from the chromatin area and was not detected by the other stainings.2)In regards to the four meiotic products,it has long been considered that only one product enters the paroral cone region(PC)and survives after meiosis.However,our protargol and immunofluorescence labeling results indicated that PC entrance of the meiotic product happened before the completion of meiosis instead of after.3)In our previous study,protargol staining indicated the presence of a swollen structure around the central part of the"U"and"V"shaped spindles connecting the two types of prospective pronuclei.However,immunofluorescence labeling with anti-a tubulin antibodies gave a different image from protargol.All these observations form the basis for further studies of their molecular mechanisms.
基金supported by the Laoshan Laboratory(LSKJ202203203)the National Natural Science Foundation of China(31961123002,32270435 and 32471688)+1 种基金the National Institutes of Health(R35-GM122566-01)the National Science Foundation(DBI-2119963,DEB-1927159 and 1911449).
文摘Paramecium,a group of ciliates with a long evolutionary history,plays essential roles in freshwater ecosystems and has been model for genetic,cellular,and evolutionary studies for over a century.Despite the valuable contributions of genomic resources such as ParameciumDB,genomic data are still mostly limited to species in and near the P.aurelia group.This study addresses this gap by HiFi sequencing,assembling,and annotating the macronuclear genomes of five rare Paramecium species:P.calkinsi,P.duboscqui,P.nephridiatum,P.putrinum,and P.woodruffi.These genomes enable a comprehensive exploration of genomic diversity,genome evolution,and phylogenomic relationships within the genus Paramecium.The genome sizes range from 47.78 to 113.16 Mb,reflecting unexpected variation in genomic content,and genic features differ from those of other reported Paramecium genomes,such as larger intron sizes and higher GC content.Nonetheless,the de novo assemblies indicate that macronuclear genomes of all Paramecium are highly streamlined,with~77%being protein-coding gene regions.Based on gene-duplication depths,synonymous mutations in paralogs,and phylogenomic relationships,we discovered that the five species experienced at least three whole-genome duplication(WGD)events,independent of those previously found in the P.aurelia complex.Using all available WGD data for Paramecium,we further explore the paralog dynamics after WGD events by modeling.This study contributed to a more comprehensive and deeper understanding of genome architecture and evolution in Paramecium.
基金supported by the National Natural Science Foundation of China(No.32270539,31961123002)the Natural Science Foundation of Shandong Province(ZR2020JQ13)+1 种基金the Fundamental Research Funds for the Central Universities(202141004)the Researchers Supporting Project Number(RSP2023R10)King Saud University,Riyadh,Saudi Arabia.
文摘Ciliated protists are highly differentiated unicellular eukaryotes that possess special sexual processes(conjugation and autogamy)that rely on their unique nuclear dimorphism,i.e.,the presence of both a germline micronucleus(MIC)and a somatic macronucleus(MAC)in a single cell.The sexual processes show a high diversity in different ciliates.To better understand the differentiation and evolution of sexual processes in closely related species,we investigated the nuclear events during conjugation in Paramecium jenningsi strain GZ,a poorly studied close relative of the well-known P.aurelia complex.The main results include:(1)the conjugation process takes about 48 h,including three prezygotic divisions(meiosis I,II,and mitosis)and three postzygotic divisions;(2)the MICs are dominated by the“parachute”phase at the prophase of meiosis I;(3)after meiosis II,a variable number of nuclei undergo the third prezygotic division,and the two products near the paroral cone become the genetically identical migratory and stationary pronuclei;(4)the synkaryon divides three times to form the MIC and the MAC anlagen,but only one nuclear product of the first postzygotic division completes the next two divisions;and(5)an extra cell division is required to complete the last step of conjugation,during which two MIC anlagen undergo mitotic division while two MAC anlagen are distributed between the daughter cells without division.The comparison of the nuclear events during conjugation in representatives of the class Oligohymenophorea reveals that usually there are three prezygotic divisions and a variable number of postzygotic divisions.However,the number of selected and differentiated nuclei after each division differs among species.This study provided a new model ciliate for further investigations of nuclear selection and differentiation as well as nuclear morphology during meiosis.
