All vertebrates have a definitive thyroid gland,or thyroid for short.As a critical organ for growth,development and metabolism,its origin and evolution have long received attention.On the basis of anatomical position,...All vertebrates have a definitive thyroid gland,or thyroid for short.As a critical organ for growth,development and metabolism,its origin and evolution have long received attention.On the basis of anatomical position,endodermal origination and histological features,the endostyle of amphioxus has been proposed as a homologue to the thyroid of vertebrates.This homology is further supported by the findings that the amphioxus endostyle abounds in thyroid hormones,possesses several thyroid-specific proteins such as thyroperoxidase,nicotinamide adenine dinucleotide phosphate(NADPH)oxidase and thyroglobulin,and expresses the thyroid-related transcription factors involved in the regulation of development of the vertebrate thyroid,including Nkx2.1,FoxE4 and Pax2/5/8.Importantly,our study on functionality,together with others,indicates significant similarities between the amphioxus endostyle and the vertebrate thyroid gland.Moreover,we show that the production of thyroid hormones by the amphioxus endostyle is mediated in a fashion similar to that of the vertebrate thyroid.These provide solid evidences that the amphioxus endostyle is the homologue of the vertebrate thyroid.From a phylogenetic viewpoint,we propose that the hypobranchial ridge,or endostyle-like structure,of hemichordates is the most primitive forerunner of the thyroid,from which the vertebrate thyroid is formed through the transformation of non-follicular endostyle of amphioxus to follicular endocrine organ of vertebrates.We also raise a couple of questions that demand further study.展开更多
Dongshan Bay,along with Xiamen Bay,serves as a significant distribution area for amphioxus in Fujian Province.In this survey,we observed that the sedimentary environment of Dongshan Bay has been seriously silted due t...Dongshan Bay,along with Xiamen Bay,serves as a significant distribution area for amphioxus in Fujian Province.In this survey,we observed that the sedimentary environment of Dongshan Bay has been seriously silted due to rapid economic development and the thriving aquaculture industry.Consequently,there has been a significant reduction in suitable habitats for amphioxus and a sharp decline in its resource abundance.Totally 9 amphioxuses were collected from its eastern region in 2022 with a population density of 18.75 ind m^(-2) and a body length from 34.15 to 48.02 mm.The amphioxuses acquired in this investigation were classified as Branchiostoma japonicum based on morphological traits,such as a cuspate rostral fin,measurements of angles between the dorsal and super-caudal fins,angles between the pre-anal and sub-caudal fins,along with an accurate count of pre-anal fin chambers which matched those observed in B.japonicum.Moreover,a molecular barcoding analysis was conducted using a fragment of the mitochondrial COI gene.The results indicated that Branchiostoma sp.from Dongshan Bay in this study belongs to B.japonicum,providing additional support for the morphological identification results.Considering amphioxuses are still surviving in Dongshan Bay despite the destruction of their habitat,it is recommended to implement measures to safeguard their resources and habitats.The measures may include designating protection areas,strengthening law enforcement management to prohibit sand mining,regulating the scale of cage aquaculture,and augmenting wild resources through artificial breeding and release.展开更多
Amphioxus has an important evolutionary position as a result of their phylogenetic position relative to vertebrates. Understanding their chromosomes would provide key points in the study of evolutionary biology and co...Amphioxus has an important evolutionary position as a result of their phylogenetic position relative to vertebrates. Understanding their chromosomes would provide key points in the study of evolutionary biology and comparative genomics. The difficulty in preparing amphioxus chromosomes currently provides a significant hurdle in this research. In the current study, we describe an improved method for metaphase preparation from amphioxus embryos and methodology for preparing metaphase spreads from regenerative somatic cells. Chromosomes of two amphioxus species from Xiamen waters in China are also observed. The diploid chromosome number was found to be 40 in Branchiostoma belcheri, while B. japonicum has 36, confirming the two are distinct species from cytotaxonomic viewpoint.展开更多
GATA factors are evolutionarily conserved and play crucial roles during embryonic development in both vertebrates and invertebrates. Vertebrate GATAs can be divided into two subgroups, the GATAI/2/3 and the GATA4/5/6 ...GATA factors are evolutionarily conserved and play crucial roles during embryonic development in both vertebrates and invertebrates. Vertebrate GATAs can be divided into two subgroups, the GATAI/2/3 and the GATA4/5/6 classes. Through genomic analysis, we have identified three GATA factors, representing the GATA1/2/3 and GATA4/5/6 subfamilies respectively, and one GATA like protein in the genome of the basal chordate amphioxus （Branchiostoma floridae, cephalochordata）. Partial sequence of GATA123 in the amphioxus Branchiostoma belcheri （BbGATA123） was cloned and its expression pattern during early embryonic development was studied. Expression of BbGATA123 is first detected in the mesendoderm during gastrulation. Interestingly, in the late neurula and early larva stages, it is expressed strongly in the cerebral vesicle and the mid gut region. Its expression is compared to Otx, a gene known crucial for the development of anterior structures. Our observations suggest that GATA123, together with Otx, might play an important role in the development of amphioxus cerebral vesicle, the counterpart of the vertebrate brain.展开更多
Actins are a small family of ubiquitous proteins that are essential cytoskeletal components and are highly conserved during evolution. Actins are usually divided into two classes, the cytoplasmic and muscle actins, wh...Actins are a small family of ubiquitous proteins that are essential cytoskeletal components and are highly conserved during evolution. Actins are usually divided into two classes, the cytoplasmic and muscle actins, which have different functional roles. Here we systematically analyzed the actin genes in the genome of the primitive chordate amphioxus （Branchiostoma floridae）. We found that amphioxus contains more than 30 actin genes, many of which are linked. Phylogenetic analysis suggests the amphioxus actin genes have clearly undergone extensive expansion through tandem duplications. The actin genes＇ structure also varies a lot, containing 2 to 7 exons. We also cloned two muscle type of actin genes from the amphioxus （B. belcheri） and compared their expression patterns during early development. The slight difference in their expression suggests functional diversification of these actin genes. Our results shed light on the evolution both of actin genes themselves and their functional roles in chordate development.展开更多
Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on...Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on its reproduction and development is necessary.The main findings in this study onthe spawning and fecundity of the amphioxus reared in laboratory and its larval development are as fol-lows.1.Water temperature markedly affected the spawning.It spawned only when water temperature reached 21℃.2.Spawning of the amphioxus in laboratory was markedly extended.Initially,the amphioxus spawned at about 7:00 PM,but spawning time was postponed as spawning days went on.3.The number of eggs produced by a female ranged from 1400 to 12800,average of 5800.This al-so represents the fecundity of the amphioxus because it shedded all eggs within the ovary at a time.4.During the first few months of life of the amphioxus,its growth rate changed seasonally.Thegrowth rate in summer and fall was greater than that展开更多
Epidermal Cells of amphioxus at different developmental stages were investigated by electron microscopy and colloidal carbon tracing experiments.Amphioxus epidermal cells showed different ultrastructural characteristi...Epidermal Cells of amphioxus at different developmental stages were investigated by electron microscopy and colloidal carbon tracing experiments.Amphioxus epidermal cells showed different ultrastructural characteristics at larval and adult stages. The epidermal cells at all larval stages studied (24-96 h) had numerous usicles containing elatron dense materials in their apical Cytoplasm. In tracing experiments, carbon particles were found in apical vesicles and intercellular spaces. Under scanning electron microscope,many crater-like protrusions were observed on the surface of the cells. These results indicated that amphioxus larva epidermal cells may be capable of endocytosis. The epidermal cells of 3-month and adult amphioxus un obviously secretory ones characterized by well -developed peripheral filaments, a prominent Golgi apparatus and abundant apical secretory vesicles. This study also showed that adult amphioxus body surfare mucus contained lectin that could aggutinate human red blood cels. The authors propose that the epidermal cells of amphioxus larva and adult may contribute to the immune defense of the animal by different means.展开更多
Information regarding antioxidant enzymes in amphioxus remains lacking, and this study was carried out to examine the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in differ...Information regarding antioxidant enzymes in amphioxus remains lacking, and this study was carried out to examine the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in different genders and tissues of amphioxus Branchiostoma belcheri tsingtauense. Results show that (1) CuZn-SOD, CAT and GPX activities in the whole amphioxus B. belcheri tsing- tauense were basically at the same levels in male and female amphioxus, whereas both T-SOD and Mn-SOD activities in male amphioxus were significantly higher than that in the female (P<0.05); (2) The testis had significantly higher T-SOD and CuZn-SOD activities than the ovary (P<0.05); (3) CuZn-SOD activity was undetectable in the guts of male and female amphioxus; (4) For both male and female am- phioxus, the activities of CAT and GPX in the gonads including testis and ovary were the lowest (P<0.05) among the tissues examined; (5) The gut and gill had the same level GPX activities while the gut had a higher CAT activity; (6) There was no clear difference in CAT and GPX activities in the corresponding tissues between male and female amphioxus. The study on SOD, CAT and GPX activities in different genders and tissues of the protochordate provides data for future comparison of amphioxus antioxidant enzymes with those of invertebrates and vertebrates.展开更多
Although amphioxus has been studied embryologically for over 130 years,little is known concerning the gonadal development of the laboratory reared animal.The present study in which the amphioxus were successfully main...Although amphioxus has been studied embryologically for over 130 years,little is known concerning the gonadal development of the laboratory reared animal.The present study in which the amphioxus were successfully maintained in the laboratory for more than one year showed that they could produce fertile eggs and sperms like their wild counterparts.展开更多
The localization of nitric oxide synthases （NOS） is dealed with in the developing gonads of amphioxus Branchiostoma belcheri tsingtauense. It was found by NADPH-diaphorase staining that （1） NOS activity was presen...The localization of nitric oxide synthases （NOS） is dealed with in the developing gonads of amphioxus Branchiostoma belcheri tsingtauense. It was found by NADPH-diaphorase staining that （1） NOS activity was present in the nuclear membranes of germinal vesicles during the entire period ofoocyte development; （2） NOS was localized in both the nuclear membranes and the perinuclear region of cytoplasm in the vitellogenetic oocytes; （3） NOS was relocated in the cortical layer in the mature egg; （4） NOS activity was present in spermatocytes, but not in the spermatogonia in the middle of October; （5） NOS was detected in both spermatozoa and spermatids as well as spermatocytes during the breeding season. This is the first report on the distribution pattern of NOS in the developing gonads in protochordates. These results suggest a role for NOS in the functioning of the nuclear membranes and yolk synthesis during oogenesis and in cell division and differentiation during spermatogenesis.展开更多
Using electron microscopic technique, ultrastructural characters of the oogonia and oocyte at the dif ferent phases of amphioxus are observed in detail in the present study.The squeezed out nucleolus, nucleolus-like b...Using electron microscopic technique, ultrastructural characters of the oogonia and oocyte at the dif ferent phases of amphioxus are observed in detail in the present study.The squeezed out nucleolus, nucleolus-like bodies and yolk nucleus at the side of nucleus are the characters in the early egg cells of the first and secondary phase.The nucleus and cytoplasm of oocyte change obviously their morphology ad structure from large growth stage to mature stage (from Stage Ⅲ to Stage V). As a result, the dense distribution of nuclear pore and the exten sion and depression of nuclear envelope are observable.Mitochondria,Golgi complex,rough endoplasm reticular and annulate lamellae,and others in the cytoplasm join in the formation of yolk granular.Their morphology and number also change correspondingly with the development and maturation of the oocyte.These results will provide a whole base for the reproductive physiology and artificial propagation as well as the resource management of amphioxus.展开更多
Timing of vegetal-endodermal cell determination in amphioxus embryos remains uncertain. We tentatively testal effects of A23187, the calcium ionophore, on the deveopment of vegetal blastomeres isolated at the 16-cell ...Timing of vegetal-endodermal cell determination in amphioxus embryos remains uncertain. We tentatively testal effects of A23187, the calcium ionophore, on the deveopment of vegetal blastomeres isolated at the 16-cell stage. It was found that when vegetal blastomres committed to endodermwere treated with A23187 prior to gastrulation, they were transformed into ectodermal cells as evidenced by the cell morphology and function characteristic of epidermis. Howver, the developmental fate of the sam blastomeres untreated or treated with DMSO at the same stage or of those treated with A23187 after gastrulation remained unchanged. Thus, vegetal-endodermal cells in amphioxus embryos are not irreversibly deermined before the gastrula stage, and artificial incarease in intracelluar Ca2+ concentration can induce transdetermination of the predetermined endodermal cells into ectodermal cells.展开更多
The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studi...The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studies of the Dkk and Kremen genes in amphioxus （Branchiostoma belcheri）. During embryonic and larval development, BbDkkl/2/4 is expressed in the posterior mesoendoderm, anterior somatic mesoderm and the pharyngeal regions. Its expression becomes restricted to the pharyngeal region on the left side at larval stages. In 45 h larvae, BbDkkl/2/4 is expressed specifically in the cerebral vesicle. BbDkk3 was only detected at larval stages in the mid-intestine region. Seven Kremen related genes were identified in the genome of the Florida amphioxus （Branchiostoma floridae）, clustered in 4 scaffolds, and are designated Kremenl-4 and Kremen-like 1-3, respectively. In B. belcheri, Kremenl is strongly expressed in the mesoendoderm during early development and Kremen3 is expressed asymmetrically in spots in the larval pharyngeal region. In luciferase reporter assays, BbDkkl/2/4 can strongly inhibit Wnt signaling, while BbDkk3, BbKremenl and BbKremen3 can not. No co-operative effect was observed between amphioxus Dkkl/2/4 and Kremens, suggesting that the interaction between Dkk and Kremen likely originated later during evolution.展开更多
Amphioxus or lancelets are regarded as a promising model animals for studying developmental mechanisms in chordates, and the evolution of vertebrate characters, because of their important phylogenetic position and the...Amphioxus or lancelets are regarded as a promising model animals for studying developmental mechanisms in chordates, and the evolution of vertebrate characters, because of their important phylogenetic position and their genomic and anatomical simplicity （Bertrand and Escriva, 2011; Holland and Yu, 2004）.展开更多
Amphioxus, also called lancelet or cephalochordate, is a promising model organism owning to its particularly evolu- tionary position, simple genome content and comparable body plan to that of vertebrates （Holland et ...Amphioxus, also called lancelet or cephalochordate, is a promising model organism owning to its particularly evolu- tionary position, simple genome content and comparable body plan to that of vertebrates （Holland et aL, 2004; Bertrand and Escriva, 2011）. However, use of amphioxus as a model or- ganism has been limited for many years because of lack of an efficient genomic modification method. Recently, several revolutionary gene targeting methods that could induce directed mutations, insertions and deletions at intended target sites, have been developed （Gaj et al., 2013）.展开更多
In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)wer...In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)were conducted in two core sites,i.e.,Huangcuo(HC)and Nanxian-Shibaxian(NX),in the Xiamen Amphioxus Nature Reserve in China.A total of 155 species of macrofauna were recorded,therein,polychaetes were dominant in terms of species number and density.Significant spatiotemporal variations of macrofaunal communities were observed.The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site.Macrofauna were more diverse and abundant in the cold seasons(winter and spring)than that in the warm seasons(summer and autumn).The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey.The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community.In addition,the density of amphioxus(include Branchiostoma japonicum and B.belcheri)was negatively correlated to that of polychaetes,bivalves,and crustaceans.Amphioxus was less likely to be found in the sediments with higher silt and clay content.Five biotic indices including Margaref’s richness index(d),Peilou’s evenness index(J′),Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study.AMBI seems suitable in assessing benthic health at the"Amphioxus Sand"habitat,and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.展开更多
The Wnt/β-catenin signaling pathway plays a crucial role in the embryonic development of metazoans. Although the pathway has been studied extensively in many model animals, its function in amphioxus, the most primiti...The Wnt/β-catenin signaling pathway plays a crucial role in the embryonic development of metazoans. Although the pathway has been studied extensively in many model animals, its function in amphioxus, the most primitive chordate, remains largely uncharacterized. To obtain basic data for functional analysis, we identified and isolated seven genes （Lrp5/6, Dvl, APC, Ckla, CklS, Gsk3β, and Gro） of the Wnt/β-catenin signaling pathway from the amphioxus （Branchiostoma floridae） genome. Phylogenetic analysis revealed that amphioxus had fewer members of each gene family than that found in vertebrates. Whole-mount in situ hybridization showed that the genes were maternally expressed and broadly distributed throughout the whole embryo at the cleavage and blastula stages. Among them, Dvl was expressed asymmetrically towards the animal pole, while the others were evenly distributed in all blastomeres. At the mid-gastrula stage, the genes were specifically expressed in the primitive endomesoderm, but displayed different patterns. When the embryo developed into the neurula stage, the gene expressions were mainly detected in either paraxial somites or the tail bud. With the development of the embryo, the expression levels further decreased gradually and remained only in some pharyngeal regions or the tail bud at the larva stage. Our results suggest that the Wnt/β-catenin pathway might be involved in amphioxus somite formation and posterior growth, but not in endomesoderm specification.展开更多
The study was made by observing the annual change of the gonadal development of amphioxus in Xiamen cohtinuously for two years from November, 1986 to November, 1988. We determined the gonadal diameter, gonadosomatic i...The study was made by observing the annual change of the gonadal development of amphioxus in Xiamen cohtinuously for two years from November, 1986 to November, 1988. We determined the gonadal diameter, gonadosomatic index of each amphioxus, and observed the histological characteristic of the gonadal development of the female and male by cut section, which provided the basis for dividing the stages gonads and the determining level of the gonadal development of amphioxus in each month.展开更多
Alkaline phosphatase(AP)activity is stage and tissue specific in Amphioxus embryoand larva.By histochemicai staining.no Ap activity was detected in Amphioxus embryos whenthey were younger than 15 h.Ap activity appeare...Alkaline phosphatase(AP)activity is stage and tissue specific in Amphioxus embryoand larva.By histochemicai staining.no Ap activity was detected in Amphioxus embryos whenthey were younger than 15 h.Ap activity appeared in the sanmites of 15-h embryo and washighest in somites 3-5.During iater development,the expression of Ap persisted in themyotomes tiüll at least the 48-h stage.AP began to appear in the posterior endoderm of 24-hlarvae.In 36-48 h iarvae.AP was expressed strongly in the whole endodernm except thepharyngeal region.By the inhibitory effect of phenylalanine on AP expression,there are twokinds of Aps expressed in the Amphioxus endoderm and myotome.The endodermal Ap wasapparently of intestinal type and the myotomal AP was prebably of non-tissue-specific type.展开更多
The cDNA of amphioxus p23, a highly conserved co-chaperone for Hsp90, was cloned into a bacterial expression vector pGEX - 6P - 1 and the GST-tagged fusion protein was produced in Eschherichia coli cells. The recombin...The cDNA of amphioxus p23, a highly conserved co-chaperone for Hsp90, was cloned into a bacterial expression vector pGEX - 6P - 1 and the GST-tagged fusion protein was produced in Eschherichia coli cells. The recombinant p23 was purified by affinity purification, and its molecular mass was estimated to be approximately 22 kDa by sodium dedecyl sulfate-polyacrylamide gel electrephoresis. The N-terminus of purified p23 was sequenced, and the resulting amino acid sequence matches exactly the predicted residues deduced from the amphioxus p23 gene. Besides, pelyclonal antibodies against the recombinant p23 were generated, and these antibodies not only recognized specifically the fusion protein GST - p23 from induced E. coli cells, purified GST - p23 and p23 protein, but also reacted with the total protein extracted fi＇om the adult amphioxus and formed a single positive band. These results pave the way for identifying its tissue and subcellular localization, and may open the door to clarifying its structure and mechanisms of biological role.展开更多
基金The National Natural Science Foundation of China under contact No.32270434.
文摘All vertebrates have a definitive thyroid gland,or thyroid for short.As a critical organ for growth,development and metabolism,its origin and evolution have long received attention.On the basis of anatomical position,endodermal origination and histological features,the endostyle of amphioxus has been proposed as a homologue to the thyroid of vertebrates.This homology is further supported by the findings that the amphioxus endostyle abounds in thyroid hormones,possesses several thyroid-specific proteins such as thyroperoxidase,nicotinamide adenine dinucleotide phosphate(NADPH)oxidase and thyroglobulin,and expresses the thyroid-related transcription factors involved in the regulation of development of the vertebrate thyroid,including Nkx2.1,FoxE4 and Pax2/5/8.Importantly,our study on functionality,together with others,indicates significant similarities between the amphioxus endostyle and the vertebrate thyroid gland.Moreover,we show that the production of thyroid hormones by the amphioxus endostyle is mediated in a fashion similar to that of the vertebrate thyroid.These provide solid evidences that the amphioxus endostyle is the homologue of the vertebrate thyroid.From a phylogenetic viewpoint,we propose that the hypobranchial ridge,or endostyle-like structure,of hemichordates is the most primitive forerunner of the thyroid,from which the vertebrate thyroid is formed through the transformation of non-follicular endostyle of amphioxus to follicular endocrine organ of vertebrates.We also raise a couple of questions that demand further study.
基金supported by grants from the Science and Technology Bureau of Xiamen(No.3502Z20227207)。
文摘Dongshan Bay,along with Xiamen Bay,serves as a significant distribution area for amphioxus in Fujian Province.In this survey,we observed that the sedimentary environment of Dongshan Bay has been seriously silted due to rapid economic development and the thriving aquaculture industry.Consequently,there has been a significant reduction in suitable habitats for amphioxus and a sharp decline in its resource abundance.Totally 9 amphioxuses were collected from its eastern region in 2022 with a population density of 18.75 ind m^(-2) and a body length from 34.15 to 48.02 mm.The amphioxuses acquired in this investigation were classified as Branchiostoma japonicum based on morphological traits,such as a cuspate rostral fin,measurements of angles between the dorsal and super-caudal fins,angles between the pre-anal and sub-caudal fins,along with an accurate count of pre-anal fin chambers which matched those observed in B.japonicum.Moreover,a molecular barcoding analysis was conducted using a fragment of the mitochondrial COI gene.The results indicated that Branchiostoma sp.from Dongshan Bay in this study belongs to B.japonicum,providing additional support for the morphological identification results.Considering amphioxuses are still surviving in Dongshan Bay despite the destruction of their habitat,it is recommended to implement measures to safeguard their resources and habitats.The measures may include designating protection areas,strengthening law enforcement management to prohibit sand mining,regulating the scale of cage aquaculture,and augmenting wild resources through artificial breeding and release.
基金Supported by grants from NSFC (No.30570208)SRFDP of Ministry of Education, China (20070384041)The Education Department of Fujian Province, China (JB07063)
文摘Amphioxus has an important evolutionary position as a result of their phylogenetic position relative to vertebrates. Understanding their chromosomes would provide key points in the study of evolutionary biology and comparative genomics. The difficulty in preparing amphioxus chromosomes currently provides a significant hurdle in this research. In the current study, we describe an improved method for metaphase preparation from amphioxus embryos and methodology for preparing metaphase spreads from regenerative somatic cells. Chromosomes of two amphioxus species from Xiamen waters in China are also observed. The diploid chromosome number was found to be 40 in Branchiostoma belcheri, while B. japonicum has 36, confirming the two are distinct species from cytotaxonomic viewpoint.
基金Supported by grants from the National Natural Science Foundation of China (30425011 30530380)~~
文摘GATA factors are evolutionarily conserved and play crucial roles during embryonic development in both vertebrates and invertebrates. Vertebrate GATAs can be divided into two subgroups, the GATAI/2/3 and the GATA4/5/6 classes. Through genomic analysis, we have identified three GATA factors, representing the GATA1/2/3 and GATA4/5/6 subfamilies respectively, and one GATA like protein in the genome of the basal chordate amphioxus （Branchiostoma floridae, cephalochordata）. Partial sequence of GATA123 in the amphioxus Branchiostoma belcheri （BbGATA123） was cloned and its expression pattern during early embryonic development was studied. Expression of BbGATA123 is first detected in the mesendoderm during gastrulation. Interestingly, in the late neurula and early larva stages, it is expressed strongly in the cerebral vesicle and the mid gut region. Its expression is compared to Otx, a gene known crucial for the development of anterior structures. Our observations suggest that GATA123, together with Otx, might play an important role in the development of amphioxus cerebral vesicle, the counterpart of the vertebrate brain.
基金supported by grants from the National Natural Science Foundation of China (30425011 30530380)the Innovation Project of Chinese Academy of Sciences (KSCX2-YW-R-090)~~
文摘Actins are a small family of ubiquitous proteins that are essential cytoskeletal components and are highly conserved during evolution. Actins are usually divided into two classes, the cytoplasmic and muscle actins, which have different functional roles. Here we systematically analyzed the actin genes in the genome of the primitive chordate amphioxus （Branchiostoma floridae）. We found that amphioxus contains more than 30 actin genes, many of which are linked. Phylogenetic analysis suggests the amphioxus actin genes have clearly undergone extensive expansion through tandem duplications. The actin genes＇ structure also varies a lot, containing 2 to 7 exons. We also cloned two muscle type of actin genes from the amphioxus （B. belcheri） and compared their expression patterns during early development. The slight difference in their expression suggests functional diversification of these actin genes. Our results shed light on the evolution both of actin genes themselves and their functional roles in chordate development.
文摘Although amphioxus is widespread in temperate and tropical seas,its population is diminishing be-cause of environmental pollution.To keep the population of this evolutionarily important animal fromdiminishing,study on its reproduction and development is necessary.The main findings in this study onthe spawning and fecundity of the amphioxus reared in laboratory and its larval development are as fol-lows.1.Water temperature markedly affected the spawning.It spawned only when water temperature reached 21℃.2.Spawning of the amphioxus in laboratory was markedly extended.Initially,the amphioxus spawned at about 7:00 PM,but spawning time was postponed as spawning days went on.3.The number of eggs produced by a female ranged from 1400 to 12800,average of 5800.This al-so represents the fecundity of the amphioxus because it shedded all eggs within the ovary at a time.4.During the first few months of life of the amphioxus,its growth rate changed seasonally.Thegrowth rate in summer and fall was greater than that
文摘Epidermal Cells of amphioxus at different developmental stages were investigated by electron microscopy and colloidal carbon tracing experiments.Amphioxus epidermal cells showed different ultrastructural characteristics at larval and adult stages. The epidermal cells at all larval stages studied (24-96 h) had numerous usicles containing elatron dense materials in their apical Cytoplasm. In tracing experiments, carbon particles were found in apical vesicles and intercellular spaces. Under scanning electron microscope,many crater-like protrusions were observed on the surface of the cells. These results indicated that amphioxus larva epidermal cells may be capable of endocytosis. The epidermal cells of 3-month and adult amphioxus un obviously secretory ones characterized by well -developed peripheral filaments, a prominent Golgi apparatus and abundant apical secretory vesicles. This study also showed that adult amphioxus body surfare mucus contained lectin that could aggutinate human red blood cels. The authors propose that the epidermal cells of amphioxus larva and adult may contribute to the immune defense of the animal by different means.
基金Supported by the Ministry of Science and Technology (MOST) of China (No.2006CB101805).
文摘Information regarding antioxidant enzymes in amphioxus remains lacking, and this study was carried out to examine the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in different genders and tissues of amphioxus Branchiostoma belcheri tsingtauense. Results show that (1) CuZn-SOD, CAT and GPX activities in the whole amphioxus B. belcheri tsing- tauense were basically at the same levels in male and female amphioxus, whereas both T-SOD and Mn-SOD activities in male amphioxus were significantly higher than that in the female (P<0.05); (2) The testis had significantly higher T-SOD and CuZn-SOD activities than the ovary (P<0.05); (3) CuZn-SOD activity was undetectable in the guts of male and female amphioxus; (4) For both male and female am- phioxus, the activities of CAT and GPX in the gonads including testis and ovary were the lowest (P<0.05) among the tissues examined; (5) The gut and gill had the same level GPX activities while the gut had a higher CAT activity; (6) There was no clear difference in CAT and GPX activities in the corresponding tissues between male and female amphioxus. The study on SOD, CAT and GPX activities in different genders and tissues of the protochordate provides data for future comparison of amphioxus antioxidant enzymes with those of invertebrates and vertebrates.
文摘Although amphioxus has been studied embryologically for over 130 years,little is known concerning the gonadal development of the laboratory reared animal.The present study in which the amphioxus were successfully maintained in the laboratory for more than one year showed that they could produce fertile eggs and sperms like their wild counterparts.
基金This work was supported by the National Natural Science Foundation of China under contract No.30470203.
文摘The localization of nitric oxide synthases （NOS） is dealed with in the developing gonads of amphioxus Branchiostoma belcheri tsingtauense. It was found by NADPH-diaphorase staining that （1） NOS activity was present in the nuclear membranes of germinal vesicles during the entire period ofoocyte development; （2） NOS was localized in both the nuclear membranes and the perinuclear region of cytoplasm in the vitellogenetic oocytes; （3） NOS was relocated in the cortical layer in the mature egg; （4） NOS activity was present in spermatocytes, but not in the spermatogonia in the middle of October; （5） NOS was detected in both spermatozoa and spermatids as well as spermatocytes during the breeding season. This is the first report on the distribution pattern of NOS in the developing gonads in protochordates. These results suggest a role for NOS in the functioning of the nuclear membranes and yolk synthesis during oogenesis and in cell division and differentiation during spermatogenesis.
文摘Using electron microscopic technique, ultrastructural characters of the oogonia and oocyte at the dif ferent phases of amphioxus are observed in detail in the present study.The squeezed out nucleolus, nucleolus-like bodies and yolk nucleus at the side of nucleus are the characters in the early egg cells of the first and secondary phase.The nucleus and cytoplasm of oocyte change obviously their morphology ad structure from large growth stage to mature stage (from Stage Ⅲ to Stage V). As a result, the dense distribution of nuclear pore and the exten sion and depression of nuclear envelope are observable.Mitochondria,Golgi complex,rough endoplasm reticular and annulate lamellae,and others in the cytoplasm join in the formation of yolk granular.Their morphology and number also change correspondingly with the development and maturation of the oocyte.These results will provide a whole base for the reproductive physiology and artificial propagation as well as the resource management of amphioxus.
文摘Timing of vegetal-endodermal cell determination in amphioxus embryos remains uncertain. We tentatively testal effects of A23187, the calcium ionophore, on the deveopment of vegetal blastomeres isolated at the 16-cell stage. It was found that when vegetal blastomres committed to endodermwere treated with A23187 prior to gastrulation, they were transformed into ectodermal cells as evidenced by the cell morphology and function characteristic of epidermis. Howver, the developmental fate of the sam blastomeres untreated or treated with DMSO at the same stage or of those treated with A23187 after gastrulation remained unchanged. Thus, vegetal-endodermal cells in amphioxus embryos are not irreversibly deermined before the gastrula stage, and artificial incarease in intracelluar Ca2+ concentration can induce transdetermination of the predetermined endodermal cells into ectodermal cells.
基金supported by the grant from the Innovation Project of Chinese Academy of Sciences (No. KSCX2-YW-R-090)
文摘The secreted Wnt signaling inhibitor Dickkopfl （Dkkl） plays key role in vertebrate head induction. Its receptor Kremen synergizes with Dkkl in Wnt inhibition. Here we have carried out expression and functional studies of the Dkk and Kremen genes in amphioxus （Branchiostoma belcheri）. During embryonic and larval development, BbDkkl/2/4 is expressed in the posterior mesoendoderm, anterior somatic mesoderm and the pharyngeal regions. Its expression becomes restricted to the pharyngeal region on the left side at larval stages. In 45 h larvae, BbDkkl/2/4 is expressed specifically in the cerebral vesicle. BbDkk3 was only detected at larval stages in the mid-intestine region. Seven Kremen related genes were identified in the genome of the Florida amphioxus （Branchiostoma floridae）, clustered in 4 scaffolds, and are designated Kremenl-4 and Kremen-like 1-3, respectively. In B. belcheri, Kremenl is strongly expressed in the mesoendoderm during early development and Kremen3 is expressed asymmetrically in spots in the larval pharyngeal region. In luciferase reporter assays, BbDkkl/2/4 can strongly inhibit Wnt signaling, while BbDkk3, BbKremenl and BbKremen3 can not. No co-operative effect was observed between amphioxus Dkkl/2/4 and Kremens, suggesting that the interaction between Dkk and Kremen likely originated later during evolution.
基金supported by the grants from National Natural Science Foundation of China (Nos.31372188,31471986 and 31672246)Fundamental Research Funds for the Central Universities, China (No.20720160056)
文摘Amphioxus or lancelets are regarded as a promising model animals for studying developmental mechanisms in chordates, and the evolution of vertebrate characters, because of their important phylogenetic position and their genomic and anatomical simplicity （Bertrand and Escriva, 2011; Holland and Yu, 2004）.
基金supported by the National Natural Science Foundation of China (Nos.31071110,30830023 and 31101631)the Scientific and Technical Innovation Committee of Shenzhen,China (No.CXZZ20120614164555920)
文摘Amphioxus, also called lancelet or cephalochordate, is a promising model organism owning to its particularly evolu- tionary position, simple genome content and comparable body plan to that of vertebrates （Holland et aL, 2004; Bertrand and Escriva, 2011）. However, use of amphioxus as a model or- ganism has been limited for many years because of lack of an efficient genomic modification method. Recently, several revolutionary gene targeting methods that could induce directed mutations, insertions and deletions at intended target sites, have been developed （Gaj et al., 2013）.
基金The National Key Research and Development Program of China under contract No.2016YFC0502904the Public Science and Technology Research Funds Projects of Oceans under contract No.201305030。
文摘In order to realize the spatiotemporal variations of benthic macrofaunal communities at the"Amphioxus Sand"habitat,six surveys including four seasons and three consecutive summers(i.e.,2014,2015 and 2016)were conducted in two core sites,i.e.,Huangcuo(HC)and Nanxian-Shibaxian(NX),in the Xiamen Amphioxus Nature Reserve in China.A total of 155 species of macrofauna were recorded,therein,polychaetes were dominant in terms of species number and density.Significant spatiotemporal variations of macrofaunal communities were observed.The density of polychaetes and the biomass of molluscs in the HC site were higher than those in the NX site.Macrofauna were more diverse and abundant in the cold seasons(winter and spring)than that in the warm seasons(summer and autumn).The annual variations of macrofaunal communities may be attributed to the changes in sediment texture among the three years of the survey.The variations in macrofaunal communities were mainly related to the proportion of polychaetes within the community.In addition,the density of amphioxus(include Branchiostoma japonicum and B.belcheri)was negatively correlated to that of polychaetes,bivalves,and crustaceans.Amphioxus was less likely to be found in the sediments with higher silt and clay content.Five biotic indices including Margaref’s richness index(d),Peilou’s evenness index(J′),Shannon-Wiener diversity index(H′),AMBI and M-AMBI were calculated in the present study.AMBI seems suitable in assessing benthic health at the"Amphioxus Sand"habitat,and a potential risk of ecological health in Xiamen Amphioxus Nature Reserve should be aware.
基金financially supported by the National Natural Science Foundation of China(31372188,31471986)the Science and Technology Innovation Commission of Shenzhen Municipality(CXZZ20120614164555920)
文摘The Wnt/β-catenin signaling pathway plays a crucial role in the embryonic development of metazoans. Although the pathway has been studied extensively in many model animals, its function in amphioxus, the most primitive chordate, remains largely uncharacterized. To obtain basic data for functional analysis, we identified and isolated seven genes （Lrp5/6, Dvl, APC, Ckla, CklS, Gsk3β, and Gro） of the Wnt/β-catenin signaling pathway from the amphioxus （Branchiostoma floridae） genome. Phylogenetic analysis revealed that amphioxus had fewer members of each gene family than that found in vertebrates. Whole-mount in situ hybridization showed that the genes were maternally expressed and broadly distributed throughout the whole embryo at the cleavage and blastula stages. Among them, Dvl was expressed asymmetrically towards the animal pole, while the others were evenly distributed in all blastomeres. At the mid-gastrula stage, the genes were specifically expressed in the primitive endomesoderm, but displayed different patterns. When the embryo developed into the neurula stage, the gene expressions were mainly detected in either paraxial somites or the tail bud. With the development of the embryo, the expression levels further decreased gradually and remained only in some pharyngeal regions or the tail bud at the larva stage. Our results suggest that the Wnt/β-catenin pathway might be involved in amphioxus somite formation and posterior growth, but not in endomesoderm specification.
文摘The study was made by observing the annual change of the gonadal development of amphioxus in Xiamen cohtinuously for two years from November, 1986 to November, 1988. We determined the gonadal diameter, gonadosomatic index of each amphioxus, and observed the histological characteristic of the gonadal development of the female and male by cut section, which provided the basis for dividing the stages gonads and the determining level of the gonadal development of amphioxus in each month.
基金National Nature Science Foundation of China(No.39670357)Chinese National Education CommitteeShandong Natural Science Foundation
文摘Alkaline phosphatase(AP)activity is stage and tissue specific in Amphioxus embryoand larva.By histochemicai staining.no Ap activity was detected in Amphioxus embryos whenthey were younger than 15 h.Ap activity appeared in the sanmites of 15-h embryo and washighest in somites 3-5.During iater development,the expression of Ap persisted in themyotomes tiüll at least the 48-h stage.AP began to appear in the posterior endoderm of 24-hlarvae.In 36-48 h iarvae.AP was expressed strongly in the whole endodernm except thepharyngeal region.By the inhibitory effect of phenylalanine on AP expression,there are twokinds of Aps expressed in the Amphioxus endoderm and myotome.The endodermal Ap wasapparently of intestinal type and the myotomal AP was prebably of non-tissue-specific type.
文摘The cDNA of amphioxus p23, a highly conserved co-chaperone for Hsp90, was cloned into a bacterial expression vector pGEX - 6P - 1 and the GST-tagged fusion protein was produced in Eschherichia coli cells. The recombinant p23 was purified by affinity purification, and its molecular mass was estimated to be approximately 22 kDa by sodium dedecyl sulfate-polyacrylamide gel electrephoresis. The N-terminus of purified p23 was sequenced, and the resulting amino acid sequence matches exactly the predicted residues deduced from the amphioxus p23 gene. Besides, pelyclonal antibodies against the recombinant p23 were generated, and these antibodies not only recognized specifically the fusion protein GST - p23 from induced E. coli cells, purified GST - p23 and p23 protein, but also reacted with the total protein extracted fi＇om the adult amphioxus and formed a single positive band. These results pave the way for identifying its tissue and subcellular localization, and may open the door to clarifying its structure and mechanisms of biological role.
