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Wolfgang Baehr - One of the best experts on this subject based on the ideXlab platform.

  • heterotrimeric kinesin 2 kif3 mediates transition zone and Axoneme formation of mouse photoreceptors
    Journal of Biological Chemistry, 2015
    Co-Authors: Li Jiang, Cecinio C Ronquillo, Bradley K Yoder, Jeanne M Frederick, Wolfgang Baehr, Robert E. Marc
    Abstract:

    Abstract Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix emb) and tamoxifen-induced (prefix tam) deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In embKif3a-/- and in embIft88-/- mice, basal bodies failed to extend transition zones (connecting cilia) with outer segments (OS), and visual pigments mistrafficked. In contrast, tamKif3a-/- and tamIft88-/- photoreceptor Axonemes disintegrated slowly post-induction, starting distally, but rhodopsin and cone pigments trafficked normally for more than two weeks, a time interval during which the OS is completely renewed. The results demonstrate that visual pigments transport to the ROS despite removal of KIF3 and IFT88, and KIF3-mediated anterograde IFT is responsible for photoreceptor transition zone (PTZ) and Axoneme formation.

  • Heterotrimeric Kinesin-2 (KIF3) mediates transition zone and Axoneme formation of mouse photoreceptors
    The Journal of biological chemistry, 2015
    Co-Authors: Li Jiang, Cecinio C Ronquillo, Bradley K Yoder, Jeanne M Frederick, Robert E. Marc, Yuxiao Wei, Wolfgang Baehr
    Abstract:

    Anterograde intraflagellar transport (IFT) employing kinesin-2 molecular motors has been implicated in trafficking of photoreceptor outer segment proteins. We generated embryonic retina-specific (prefix "emb") and adult tamoxifen-induced (prefix "tam") deletions of KIF3a and IFT88 in adult mice to study photoreceptor ciliogenesis and protein trafficking. In (emb)Kif3a(-/-) and in (emb)Ift88(-/-) mice, basal bodies failed to extend transition zones (connecting cilia) with outer segments, and visual pigments mistrafficked. In contrast, (tam)Kif3a(-/-) and (tam)Ift88(-/-) photoreceptor Axonemes disintegrated slowly post-induction, starting distally, but rhodopsin and cone pigments trafficked normally for more than 2 weeks, a time interval during which the outer segment is completely renewed. The results demonstrate that visual pigments transport to the retinal outer segment despite removal of KIF3 and IFT88, and KIF3-mediated anterograde IFT is responsible for photoreceptor transition zone and Axoneme formation.

Jordi Miquel - One of the best experts on this subject based on the ideXlab platform.

  • Sperm characteristics in the digenean Diplodiscus amphichrus (Paramphistomoidea, Diplodiscidae), a parasite of the Chinese edible frog Hoplobatrachus rugulosus
    Zoomorphology, 2020
    Co-Authors: Papa Mbagnick Diagne, Alexis Ribas, Srisupaph Poonlaphdecha, Jordi Miquel
    Abstract:

    The ultrastructural characteristics of the mature spermatozoon of Diplodiscus amphichrus (Digenea, Paramphistomoidea, Diplodiscidae) and their ultrastructural organisation were examined by means of transmission electron microscopy. Live digeneans were collected from the Chinese edible frog Hoplobatrachus rugulosus in Thailand. The male gamete of D. amphichrus is a filiform cell with two Axonemes of the 9 + ’1’ trepaxonematan pattern, nucleus, one mitochondrion, parallel cortical microtubules, a well-developed lateral expansion, external ornamentation of the plasma membrane, spine-like bodies, and granules of glycogen. These ultrastructural characteristics have already been described in other paramphistomoids studied so far except for the cladorchiids, which present some differences. Two characteristics of the male gamete of D. amphichrus were found for the first time in a digenean: (i) the appearance of the initial part of the lateral expansion before the Axonemes in the anterior extremity and (ii) the separation between the second Axoneme and the nucleus in the posterior tip. Our results are compared with the available data in the Digenea and particularly with other paramphistomoids.

  • Spermatological characteristics of Siphoderina aloysiae (Digenea, Cryptogonimidae), an intestinal parasite of Sciaena umbra (Teleostei, Sciaenidae)
    Zoomorphology, 2019
    Co-Authors: Hichem Kacem, Jordi Miquel
    Abstract:

    The ultrastructural organisation of the spermatozoon of Siphoderina aloysiae (Digenea, Cryptogonimidae) is described based upon examination by transmission electron microscopy. Live digeneans were collected from the digestive tract of the Brown meagre Sciaena umbra (Teleostei: Sciaenidae), caught off the Gulf of Gabès in La Chebba (Tunisia). The male gamete of S. aloysiae is a filiform cell, tapered at both extremities, and exhibits typical characteristics of digenean sperm such as two Axonemes showing the 9 + ‘1’ trepaxonematan pattern with different lengths. The first Axoneme is disorganised and disappears near the anterior nuclear extremity. However, the second Axoneme reaches the posterior extremity of the spermatozoon. The latter also contains a nucleus, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. Cortical microtubules are absent in the anterior extremity of the spermatozoon and appear after the disappearance of the electron-dense material. In addition, the male gamete of S. aloysiae has two mitochondria. The first mitochondrion is associated with the external ornamentation of the plasma membrane and spine-like bodies. The second is more posteriorly located at the nuclear region after the disappearance of the first Axoneme. The present study provides new data on the mature male gamete of S. aloysiae that may be useful for the understanding of digenean relationships and phylogenetic studies.

  • Spermatological characteristics of Siphoderina aloysiae (Digenea, Cryptogonimidae), an intestinal parasite of Sciaena umbra (Teleostei, Sciaenidae)
    Zoomorphology, 2019
    Co-Authors: Hichem Kacem, Jordi Miquel
    Abstract:

    The ultrastructural organisation of the spermatozoon of Siphoderina aloysiae (Digenea, Cryptogonimidae) is described based upon examination by transmission electron microscopy. Live digeneans were collected from the digestive tract of the Brown meagre Sciaena umbra (Teleostei: Sciaenidae), caught off the Gulf of Gabes in La Chebba (Tunisia). The male gamete of S. aloysiae is a filiform cell, tapered at both extremities, and exhibits typical characteristics of digenean sperm such as two Axonemes showing the 9 + ‘1’ trepaxonematan pattern with different lengths. The first Axoneme is disorganised and disappears near the anterior nuclear extremity. However, the second Axoneme reaches the posterior extremity of the spermatozoon. The latter also contains a nucleus, two bundles of parallel cortical microtubules, external ornamentation of the plasma membrane, spine-like bodies and granules of glycogen. Cortical microtubules are absent in the anterior extremity of the spermatozoon and appear after the disappearance of the electron-dense material. In addition, the male gamete of S. aloysiae has two mitochondria. The first mitochondrion is associated with the external ornamentation of the plasma membrane and spine-like bodies. The second is more posteriorly located at the nuclear region after the disappearance of the first Axoneme. The present study provides new data on the mature male gamete of S. aloysiae that may be useful for the understanding of digenean relationships and phylogenetic studies.

  • Ultrastructural characters of the spermatozoon of the liver fluke Opisthorchis viverrini (Poirier, 1886) (Opisthorchiidae)
    Parasitology Research, 2017
    Co-Authors: Jordi Miquel, Zdzisław Świderski, Banchob Sripa, Alexis Ribas
    Abstract:

    The present study records the ultrastructural organization of the mature spermatozoon of Opisthorchis viverrini by means of transmission electron microscopy. The spermatozoon of O. viverrini is a filiform cell, tapered at both extremities. It exhibits the characteristics of type IV spermatozoon of digeneans, namely with two Axonemes of the 9+‘1’ trepaxonematan pattern, external ornamentation of the plasma membrane associated with cortical microtubules that are in the posterior part of the anterior region of the sperm cell, and with two mitochondria. The maximal number of cortical microtubules is in the anterior part of the spermatozoon and arranged into two bundles. Other characteristics are spine-like bodies and a posterior extremity with only the second Axoneme. Ultrastructural characters of the spermatozoon of O. viverrini are compared with those of other known digeneans belonging to the Opisthorchioidea, with particular emphasis on representatives of the family Opisthorchiidae. The main differences between O. viverrini and its congener Opisthorchis felineus are the spine-like bodies (present and absent, respectively) and the posterior spermatozoon character (Axoneme and nucleus, respectively).

  • ultrastructural characters of the spermatozoon of the digenean hypocreadium caputvadum kacem et al 2011 lepocreadioidea lepocreadiidae an intestinal parasite of balistes capriscus in tunisia
    Comptes Rendus Biologies, 2012
    Co-Authors: Hichem Kacem, Abdoulaye J. S. Bakhoum, Catarina Eira, Lassad Neifar, Jordi Miquel
    Abstract:

    Abstract The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabes, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two Axonemes of different lengths exhibiting the classical 9 + “1” trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second Axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the Axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Romano Dallai - One of the best experts on this subject based on the ideXlab platform.

  • the evolution of sperm Axoneme structure and the dynein heavy chain complement in cecidomid insects
    Cytoskeleton, 2016
    Co-Authors: Silvia Ciolfi, Caterina Mencarelli, Romano Dallai
    Abstract:

    The 9 + 2 Axoneme of cilia and flagella is specialized machinery aimed at the production of efficient, finely tuned motility, and it has been evolutionarily conserved from protists to mammals. However, the sperm cells of several insects express unconventional Axonemes, which represent unique models for studying the structural-functional relationships underlying axonemal function and evolution. Cecidomids comprise a group of dipterans characterized by an overall tendency to deviate from the standard axonemal pattern. In particular, the subfamily Cecidomyiinae shows a series of progressive modifications of the sperm Axoneme. We previously analyzed the unusual sperm Axonemes of Asphondylia ruebsaameni (Asphondyliidi) and Monarthropalpus buxi (Cecidomyiidi), which are characterized by the absence of any structure related to the control of motility (that is, the central pair complex, radial spokes and inner dynein arms); however, these sperm are motile, and motility is driven by the outer dynein arms only. This simplification of the motility machinery is accompanied by a parallel reduction in the dynein isoform complement. Here, we complete our survey of the axonemal organization and the parallel evolution of sperm dynein complement in cecidomids with the characterization of both the sperm ultrastructure and the dynein genes in Dryomyia lichtensteini, a representative of Lasiopteridi, the cecidomid taxon with aberrant and immotile sperm cells. On the basis of the whole set of our data, we discuss the potential molecular mechanism(s) underlying the progressive modification of Axoneme in cecidomids, leading first to a reduction of dynein genes and eventually to the complete loss of motility.

  • ultrastructure of the sperm Axoneme and molecular analysis of axonemal dynein in ephemeroptera insecta
    Cytoskeleton, 2014
    Co-Authors: Caterina Mencarelli, Romano Dallai, David Mercati, Pietro Lupetti
    Abstract:

    The Ephemeroptera sperm Axoneme is devoid of outer dynein arms (ODA) and exhibits a pronounced modification of the central pair complex (CPC), which is substituted by the central sheath (CS): a tubular element of unknown molecular composition. We performed a detailed ultrastructural analysis of sperm Axonemes in the genera Cloeon and Ecdyonurus using quick-freeze, deep-etch electron microscopy, showing that the loss of the conventional CPC is not only concomitant with the loss of ODA, but also with a substantial modification in the longitudinal distribution of both radial spokes (RS) and inner dynein arms (IDA). Such structures are no longer distributed following the alternation of different repeats as in the 9 + 2 Axoneme, but instead share a 32 nm longitudinal repeat: a multiple of the 8 nm repeat observed along the CS wall. Differently from the conventional CPC, the CS and the surrounding RS possess a ninefold symmetry, coherently with the three-dimensional pattern of motility observed in Cloeon free spermatozoa. Biochemical analyses revealed that ultrastructural modifications are concomitant with a reduced complexity of the IDA heavy chain complement. We propose that these structural and molecular modifications might be related to the relief from the evolutionary constraints imposed by the CPC on the basal 9 + 9 + 2 Axoneme and could also represent the minimal set compatible with flagellar beating and progressive motility mechanically regulated as suggested by the geometric clutch hypothesis. © 2014 Wiley Periodicals, Inc.

  • THE SPERMATOZOON OF ARTHROPODA XXX. The Multiflagellate Spermatozoon in the Termite
    2013
    Co-Authors: Mastotermes Darwiniensis, B Baccetyi, Romano Dallai
    Abstract:

    In this paper the spermatozoon of the termite Mastotermes darwinien~is is described. It is the first example of a multiflagellate sperm cell in animals. The sperm consists of a conical head and-100 flagella. Other remarkable features of this sperm cell are the absence of an acrosome, the presence of centrioles containing doublet microtubules instead of triplets, and the presence of Axonemes devoid of central tubules and with doublets bearing only one arm. The flagella are feebly motile. KEY WORDS spermatozoon multiflageUate 9 Axoneme doublets termites microtubules centrioles Studies in comparative spermatology carried out for many years by light and electron microscopy have demonstrated that in plants (22) the spermatozoid, when present, is provided with one or many pairs of flagella (only a few exceptional fungi have only a single Axoneme), whereas in animals (3) the spermatozoon generally has a single flagellum arising from the distal centriole, and only in a few instances do two flagella arise from both centrioles. Two Axonemes have been found in most platyhelminths (17), one gastrotrichian (33), some Rhynchotoid insects (7), a cecydomyid dipteran (4), several teleost and dipnoid families (25), and the Japanese frog Rhacophalus arborea (3). Only the microgamete of the protozoan Eimeria perforans has three Axonemes (28). During our investigations on Arthropoda spermatozoa, we found that spermatozoa of the termite Mastotermes darwiniensis invariably have-100 flagella. We will describe here for the first time this multiflagellate spermatozoon in animals. MATERIAI ~ AND METHODS Adult males of Mastotermes darwiniensis termites were supplied to us alive by Prof. D. Waterhouse (Division of Entomology, Canberra, Australia). Living spermatozoa in the male body fluid were observed under the interference Nomarski microscope. The termites were dissected and the testes and ducts were fixed in 4 % paraformaldehyde and 5 % glutaraldehyde in cacodylate buffer, pH 7.2. The dehydrated tissue were embedded in Epon, sectioned on an LKB III Ultrotome (LKB Produkter, Bromma, Sweden), stained with uranyl acetate and lead citrate, and observed in the Philips 301 electron microscope. DNA was detected with the EDTA regressive method o

  • the spermatogenesis and sperm structure of acerentomon microrhinus protura hexapoda with considerations on the phylogenetic position of the taxon
    Zoomorphology, 2010
    Co-Authors: Romano Dallai, David Mercati, Giuliano Callaini, Y W Yin, Maria Giovanna Riparbelli
    Abstract:

    The spermatogenesis of the proturan Acerentomon microrhinus Berlese, (Redia 6:1–182, 1909) is described for the first time with the aim of comparing the ultrastructure of the flagellated sperm of members of this taxon with that of the supposedly related group, Collembola. The apical region of testes consists of a series of large cells with giant polymorphic nuclei and several centrosomes with 14 microtubule doublets, whose origin is likely a template of a conventional 9-doublet centriole. Beneath this region, there are spermatogonial cells, whose centrosome has two centrioles, both with 14 microtubule doublets; the daughter centriole of the pair has an axial cylinder. Slender parietal cells in the testes have centrioles with nine doublet microtubules. Spermatocytes produce short primary cilia with 14 microtubule doublets. Spermatids have a single basal body with 14 microtubule doublets. Anteriorly, a conical dense material is present, surrounded by a microtubular basket, which can be seen by using an α-anti-tubulin antibody. Behind this region, the basal body expresses a long Axoneme of 14 microtubule doublets with only inner arms. An acrosome is lacking. The nucleus is twisted around the apical conical dense structure and the Axoneme; this coiling seems to be due to the rotation of the Axoneme on its longitudinal axis. The posterior part of the Axoneme forms three turns within the spermatid cytoplasm. Few unchanged mitochondria are scattered in the cytoplasm. Sperm consist of encysted, globular cells that descend along the deferent duct lumen. Some of them are engulfed by the epithelial cells, which thus have a spermiophagic activity. Sperm placed in a proper medium extend their flagellar Axonemes and start beating. Protura sperm structure is quite different from that of Collembola sperm; and on the basis of sperm characters, a close relationship between the two taxa is not supported.

  • ultrastructural analysis of the aberrant Axoneme morphogenesis in thrips thysanoptera insecta
    Cytoskeleton, 2007
    Co-Authors: Eugenio Paccagnini, Caterina Mencarelli, Björn A. Afzelius, David Mercati, Romano Dallai
    Abstract:

    Thrips spermiogenesis is characterized by unusual features in the differentiating spermatid cells. Three centrioles from which three individual short flagella are initially assembled, make the early spermatid a tri-flagellated cell. Successively, during spermatid maturation, the three basal bodies maintain a position close to the most anterior end of the elongating nucleus, so that the three Axonemes are progressively incorporated in the spermatid cytoplasm, where they run in parallel to the main nuclear axis. Finally, the three Axonemes amalgamate to form a microtubular bundle. The process starts with the formation of rifts at three specific points in each axonemal circumference, corresponding to sites 1,3,7 and leads to the formation of 9 microtubular rows of different length, i.e. 3 ""dyads"", 3 ""triads"" and 3 ""tetrads"". In the spermatozoon, the nucleus, the mitochondrion and the bundle of microtubules are arranged in a helicoidal pattern. The elongation of the spermatozoon is allowed by the deep anchorage of the spermatid to the cyst cell through a dense mass of material which, at the end of spermiogenesis, becomes a long anterior cylindrical structure. This bizarre ""Axoneme"" does not show any trace of progressive movement but it is able to beat. According to the presence of dynein arms, sliding can take place only within each row and not between the rows. The possible molecular basis underlying the peculiar instability of thrips Axonemes is discussed in light of the present knowledge on the organization of the Axoneme in mutant organisms carrying alterations of the tubulin molecule. Cell Motil.

Bernard Marchand - One of the best experts on this subject based on the ideXlab platform.

  • ultrastructure of the spermatozoon of labracetabulum gephyroberici digenea opecoelidae intestinal parasite of gephyroberyx darwinii teleostei trachichtyidae in senegal
    Zoologischer Anzeiger, 2020
    Co-Authors: Aïssatou Bâ, Abdoulaye J. S. Bakhoum, P Ndiaye, Cheikh Tidiane Ba, Bernard Marchand, Rodney A Bray, Yann Quilichini
    Abstract:

    Abstract This work is the first ultrastructural study of spermatozoa in a species of Digenea belonging to the genus Labracetabulum. Labracetabulum gephyroberici parasitizes the digestive tract of the teleost fish Gephyroberyx darwinii (Trachichtyidae) captured in the Atlantic Ocean near Dakar (Senegal). This is also the first report of L. gephyroberici from Senegal. The mature spermatozoon is filiform tapered at both ends and exhibits the general organization described in most Opecoelideans, namely two Axonemes of the 9 + “1” pattern of the Trepaxonemata, an anterior electron-dense material, an external ornamentation associated with a row of cortical microtubules, spine-like bodies, two mitochondria and two bundles of cortical microtubules. However, the mature spermatozoon of L. gephyroberici exhibits some particularities: a short first Axoneme which does not reach the nuclear region and the position of the second mitochondrion which reaches almost the posterior part of the mature spermatozoon. The second mitochondrion is still present after the disappearance of the second Axoneme. The morphology of the posterior extremity corresponds to the Opecoelidean type described by Quilichini et al. (2010).

  • sperm ultrastructure of podocotyloides magnatestis digenea opecoeloidea opecoelidae a parasite of parapristipoma octolineatum pisces teleostei
    Zoologischer Anzeiger – A Journal of Comparative Zoology, 2016
    Co-Authors: Papa Mbagnick Diagne, Bernard Marchand, Rodney A Bray, Papa Ndiaye, Yann Quilichini
    Abstract:

    Abstract The mature Podocotyloides magnatestis spermatozoon exhibits two Axonemes of the 9 + “1” pattern of the Trepaxonemata, a nucleus, two mitochondria, two bundles of parallel cortical microtubules, spine-like bodies, an external ornamentation of plasma membrane, glycogen granules and an antero-lateral electron-dense material. These ultrastructural characteristics have already been described in the Opecoeloidea species studied so far. However, P. magnatestis spermatozoon is distinguished by the fact that its electron-dense material is laterally located on the side of the second Axoneme. Moreover, the posterior spermatozoon extremity, characterized by the presence of the nucleus, is observed for the first time in the Opecoelidae.

  • ultrastructural study of the spermatozoon of hemiurus appendiculatus digenea hemiuroidea hemiuridae a parasite of boops boops pisces teleostei sparidae off senegal
    Tissue & Cell, 2016
    Co-Authors: Ayatoulaye Dione, P Ndiaye, Cheikh Tidiane Ba, Yann Quilichini, Papa Mbagnick Diagne, Bernard Marchand
    Abstract:

    The mature spermatozoon of Hemiurus appendiculatus exhibits the general pattern described in most of the digenean namely, two Axonemes of the 9 + "1" pattern of the Trepaxonemata, a nucleus, a filiform mitochondrion, external ornamentations of the plasma membrane and parallel cortical microtubules located on one side of the spermatozoon. In this study, we show for the second time in a digenean spermatozoon the presence of microtubules of the second Axoneme associated each in a short length with an external ornamentation, seven cortical microtubules, a terminal bulge in the anterior spermatozoon extremity separate from the remainder of the spermatozoon by a transverse constriction and the simultaneous presence of the external ornamentation of the plasma membrane with a filamentous ornamentation. The external ornamentations have a differentiated distribution, cover almost the anterior region of the spermatozoon, are more abundant around the first Axoneme and extend backwards over a short distance around the second Axoneme. This study also allowed us to reveal for the first time the existence in the Hemiuroidea of an Axoneme that begins to disrupt before reaching the front end of the mitochondrion.

  • Ultrastructural characters of the spermatozoa in Digeneans of the genus Lecithochirium Lühe, 1901 (Digenea, Hemiuridae), parasites of fishes: comparative study of L. microstomum and L. musculus.
    Parasite, 2014
    Co-Authors: Papa Ibnou Ndiaye, Yann Quilichini, Aminata Sène, Vasyl V Tkach, Bernard Marchand
    Abstract:

    This study provides the first ultrastructural data of spermatozoa in the genus Lecithochirium. The spermatozoa of L. microstomum (from Trichiurus lepturus in Senegal) and L. musculus (from Anguilla anguilla in Corsica) exhibit the general pattern described in the great majority of the Digenea, namely two Axonemes with the 9 + "1" pattern typical of the Trepaxonemata, one mitochondrion, a nucleus, parallel cortical microtubules and external ornamentation of the plasma membrane. Spermatozoa of L. microstomum and L. musculus have some specific features such as the presence of a reduced number of cortical microtubules arranged on only one side of the spermatozoon, the lack of spine-like bodies and expansion of the plasma membrane. The external ornamentation of the plasma membrane entirely covers the anterior extremity of the spermatozoa. The ultrastructure of the posterior extremity of the spermatozoa corresponds to the pattern previously described in the Hemiuridae, characterized by only singlets of the second Axoneme. A particularity of these spermatozoa is the organization of the microtubule doublets of the second Axoneme around the nucleus in the posterior part of the spermatozoon.

  • spermatozoon ultrastructure of gyliauchen sp digenea gyliauchenidae an intestinal parasite of siganus fuscescens pisces teleostei
    The Biological Bulletin, 2011
    Co-Authors: Yann Quilichini, Josephine Foata, Jean-lou Justine, Rodney A Bray, Bernard Marchand
    Abstract:

    The ultrastructure of the mature spermatozoon of Gyliauchen sp., a parasite of the dusky rabbitfish Siganus fuscescens, was studied by transmission electron microscopy. The spermatozoon possesses two Axonemes of the 9+“1” pattern of Trepaxonemata, four attachment zones, one mitochondrion, a nucleus, cortical microtubules, external ornamentation of the plasma membrane, and spine-like bodies. The main characteristics of this spermatozoon are the presence of one mitochondrion, spine-like bodies not associated with the external ornamentation, and a posterior extremity of type 3 that is characterized by the following sequence: posterior extremity of the nucleus then posterior extremity of the second Axoneme. Numerous other ultrastructural features are also discussed and compared to the digenean spermatology literature. This is the first study of a member of the Gyliauchenidae and the fourth within the Lepocreadioidea. The results show that many ultrastructural characters are variable within this superfamily an...

Elizabeth C Raff - One of the best experts on this subject based on the ideXlab platform.

  • Axoneme β tubulin sequence determines attachment of outer dynein arms
    Current Biology, 2008
    Co-Authors: Elizabeth C Raff, Ellen Popodi, Henry D Hoyle, Rudolf F Turner
    Abstract:

    Summary Axonemes of motile eukaryotic cilia and flagella have a conserved structure of nine doublet microtubules surrounding a central pair of microtubules. Outer and inner dynein arms on the doublets mediate Axoneme motility [1]. Outer dynein arms (ODAs) attach to the doublets at specific interfaces [2–5]. However, the molecular contacts of ODA-associated proteins with tubulins of the doublet microtubules are not known. We report here that attachment of ODAs requires glycine 56 in the β-tubulin internal variable region (IVR). We show that in Drosophila spermatogenesis, a single amino acid change at this position results in sperm Axonemes markedly deficient in ODAs. Moreover, we found that axonemal β-tubulins throughout the phylogeny have invariant glycine 56 and a strongly conserved IVR, whereas nonaxonemal β-tubulins vary widely in IVR sequences. Our data reveal a deeply conserved physical requirement for assembly of the macromolecular architecture of the motile Axoneme. Amino acid 56 projects into the microtubule lumen [6]. Imaging studies of Axonemes indicate that several proteins may interact with the doublet-microtubule lumen [3, 4, 7, 8]. This region of β-tubulin may determine the conformation necessary for correct attachment of ODAs, or there may be sequence-specific interaction between β-tubulin and a protein involved in ODA attachment or stabilization.

  • Axoneme dependent tubulin modifications in singlet microtubules of the drosophila sperm tail
    Cytoskeleton, 2008
    Co-Authors: Henry D Hoyle, Rudolf F Turner, Elizabeth C Raff
    Abstract:

    Drosophila melanogaster sperm tubulins are posttranslationally glutamylated and glycylated. We show here that Axonemes are the substrate for these tubulin C-terminal modifications. Axoneme architecture is required, but full length, motile Axonemes are not necessary. Tubulin glutamylation occurs during or shortly after assembly into the Axoneme; only glutamylated tubulins are glycylated. Tubulins in other testis microtubules are not modified. Only a small subset of total Drosophila sperm Axoneme tubulins have these modifications. Biochemical fractionation of Drosophila sperm showed that central pair and accessory microtubules have the majority of poly-modified tubulins, whereas doublet microtubules have only small amounts of mono- and oligo-modified tubulins. Glutamylation patterns for different β-tubulins experimentally assembled into Axonemes were consistent with utilization of modification sites corresponding to those identified in other organisms, but surrounding sequence context was also important. We compared tubulin modifications in the 9 + 9 + 2 insect sperm tail Axonemes of Drosophila with the canonical 9 + 2 Axonemes of sperm of the sea urchin Lytichinus pictus and the 9 + 0 motile sperm Axonemes of the eel Anguilla japonica. In contrast to Drosophila sperm, L. pictus sperm have equivalent levels of modified tubulins in both doublet and central pair microtubule fractions, whereas the doublets of A. japonica sperm exhibit little glutamylation but extensive glycylation. Tubulin C-terminal modifications are a prevalent feature of motile Axonemes, but there is no conserved pattern for placement or amount of these modifications. We conclude their functions are likely species-specific. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc.

  • Axoneme specialization embedded in a generalist β tubulin
    Cytoskeleton, 2008
    Co-Authors: Ellen Popodi, Rudolf F Turner, Henry D Hoyle, Spencer Kruse, Elizabeth C Raff
    Abstract:

    The relationship between the primary structure of the β-tubulin C-terminal tail (CTT) and Axoneme structure and function is explored using the spermatogenesis-specific β2-tubulin of Drosophila. We previously showed that all β-tubulins used for motile 9 + 2 Axonemes contain a conserved sequence motif in the proximal part of the CTT, the β-tubulin Axoneme motif. The differential ability of tubulin isoforms and abilities of β2-tubulin C-terminal truncations to form Axonemes led us to hypothesize that the Axoneme motif is essential for Axoneme formation and the distal half of the CTT was less important. The studies we report here indicate that it is not that simple. Unexpectedly, some changes in the core sequence of the Axoneme motif did not disrupt formation of motile Axonemes. And, while deletion of the distal CTT did not disrupt the ability to produce functional sperm [Popodi et al., Cell Motil Cytoskeleton 2005;62:48–64], changing the amino acid sequence in this region can. Thus both regions are important. The deep conservation of the Axoneme motif in all eukaryotic groups implies that the presence of the sequence motif confers a functional advantage. The central pair is the Axoneme structure most sensitive to perturbations in tubulin molecules; we hypothesize central pair assembly is facilitated by the presence of this motif. Our data reveal that β2-tubulin has robust properties for Axoneme assembly, and that axonemal specializations are embedded in both the CTT and the body of the β2 molecule. Cell Motil. Cytoskeleton 2008. © 2007 Wiley-Liss, Inc.

  • the proximal region of the β tubulin c terminal tail is sufficient for Axoneme assembly
    Cytoskeleton, 2005
    Co-Authors: Ellen Popodi, Rudolf F Turner, Henry D Hoyle, Elizabeth C Raff
    Abstract:

    We have used Drosophila testis-specific beta2-tubulin to determine sequence requirements for different microtubules. The beta2-tubulin C-terminal tail has unique sperm-specific functions [Dev Biol 158:267-286 (2003)] and is also important for forming stable heterodimers with alpha-tubulin, a general function common to all microtubules [Mol Biol Cell 12(7):2185-2194 (2001)]. beta-tubulins utilized in motile 9 + 2 Axonemes contain a C-terminal sequence "Axoneme motif" [Science 275 (1997) 70-73]. C-terminal truncated beta2-tubulin cannot form the sperm tail Axoneme. Here we show that a partially truncated beta2-tubulin (beta2Delta7) containing only the proximal portion of the C-terminal tail, including the Axoneme motif, can support production of functional motile sperm. We conclude that these proximal eight amino acids specify the binding site for protein(s) essential to support assembly of the motile Axoneme. Males that express beta2Delta7, although they are fertile, produce fewer sperm than wild type males. Beta2Delta7 causes a slightly increased error rate in spermatogenesis attributable to loss of stabilizing properties intrinsic to the full-length C-terminal tail. Therefore, beta2Delta7 males would be at a selective disadvantage and it is likely that the full-length C-terminus would be essential in the wild and in evolution.

  • the best of all worlds or the best possible world developmental constraint in the evolution of beta tubulin and the sperm tail Axoneme
    Evolution & Development, 2002
    Co-Authors: Mark Nielsen, Elizabeth C Raff
    Abstract:

    Through evolutionary history, some features of the phenotype show little variation. Stabilizing selection could produce this result, but the possibility also exists that a feature is conserved because it is developmentally constrained--only one or a few developmental mechanisms can produce that feature. We present experimental data documenting developmental constraint in the assembly of the motile sperm tail Axoneme. The 9+2 microtubule architecture of the eukaryotic Axoneme has been deeply conserved. We argue that the quality of motility supported by Axonemes with this morphology explains their long conservation, rather than a developmental necessity for the 9+2 architecture. However, our functional tests in Drosophila spermatogenesis reveal considerable constraint in the coevolution of testis-specific beta-tubulin and the sperm tail Axoneme. The evolution of testis beta-tubulins used in insect sperm tail Axonemes is highly punctuated, indicating some pressure acting on their evolution. We provide a mechanistic explanation for their punctuated evolution by testing structure-function relationships between testis beta-tubulin and the motile Axoneme in D. melanogaster. We discovered that a highly conserved sequence feature of beta-tubulins used in motile Axonemes is needed to specify central pair formation. Second, our data suggest that cooperativity in the function of internal beta-tubulin amino acids is needed to support the long Axonemes characteristic of Drosophila sperm tails. Thus, central pair formation constrains the evolution of the Axoneme motif, and intramolecular cooperativity makes the evolution of the internal residues path dependent, which slows their evolution. Our results explain why a highly specialized beta-tubulin is needed to construct the Drosophila sperm tail Axoneme. We conclude that these constraints have fixed testis-specific beta-tubulin identity in Drosophila.