Studies of Spermatogenesis in the Hepaticae. Iv. On the Blepharoplast of Blasia

Carothers, Zane B.

doi:10.1002/j.1537-2197.1973.tb07594.x

Cited by 38 publications

(24 citation statements)

References 10 publications

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“…Antithetically, colchicine produces irregularities in both the cytoskeletal (MLS) and axonemal tubules in Nitella [Turner, 19701 ,Marsilea [Myles and Hepler, 1977a,b], and Ceratopteris [Duckett, unpublished data]. However, it should be noted that Wilkinson et al [1975] were able to distinguish between these two classes of tubules in D m sophila spermatids on the basis of vinblastine treatmentall but the cross-linked manchette tubules were absent in the presence o f the drug, phytes [Carothers, 1973[Carothers, , 1975Kreitner, 1977a,b;Kreitner and Carothers, 1976;Moser et al, 19771 and pteridophytes [Carothers et al, 1975;Duckett, 1973Duckett, ,1975Duckett and Bell, 1977;Myles and Hepler, 1977a,b] , there is general agreement that the lamellar strip constitutes an elaborate microtubule-organizing center responsible for the coordinated assembly of the overlying microtubular band. The only ordered arrays of regularly spaced microtubules in 230X are those in contact with the MLS lamellar strip; and this is strong supporting evidence for this hypothesis.…”

Section: The Multilayered Structurementioning

confidence: 99%

Ultrastructural studies of mutant spermatozoids in ferns. I. The mature nonmotile spermatozoid of mutation 230X in Ceratopteris thalictroides(L.)Brongn

1979

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Electron microscopy reveals that nonmotility in the spermatozoids of mutant 230X of the fern Ceratopteris thalictroides results from highly aberrant flagella. With respect to its mitochondrial complement, amyloplasts, condensed chromatin within the nucleus and the multilayered structure (MLS), the mutation is almost indistinguishable from the wild‐type spermatozoids. In contrast to flagellar mutations in other organisms (man, mouse, Drosophila, Chlamydomonas), which principally affect the microtubules of the axoneme, the basal body cartwheel is lacking in 230X. In its absence, compound microtubules with shared walls are still present, but in highly disorganized arrays. Since the amount of polymerized tubulin in the spermatozoids of 230X is approximately the same as in the wild type, the mutation does not seem to affect microtubule synthesis or assembly. Centriolar cartwheels appear to be essential templates for the alignment of triplet and doublet tubules in regular radial arrays. The MLS in 230X is almost normal, whereas the flagella are aberrant, indicating that there are two distinct functional classes of microtubules in archegoniate spermatozoids. In contrast to the helix of 3½ gyres found in the wild type, nuclear morphology in 230X exhibits profound distortions ranging from deep channels and holes to supernumerary attenuated arms. Parts of nuclei associated with the MLS are almost normal, but malformations are in variably associated with the presence of microtubules of the aberrant flagella that are in close proximity t o the nuclear surface. The shapes of the teratologies are directly related to the number and configuration of the adjacent perinuclear tubules. From these findings, it is argued that microtubules have a crucial role in nuclear shaping in archegoniates; and that the precise form of the nucleus is closely related to the geometry and development of the MLS. On the other hand, it is difficult to envisage how microtubules growing in the chaotic arrays found in 230X could themselves generate shaping forces, More likely, the actual force‐generating system, situated in or near the nuclear envelope, has become misaligned and severely restricted by the perinuclear arrays of flagellar tubules, which function as cytoskeletal elements additional to those of the normal MLS. Archegoniate plants are particularly advantageous for the detection of basal body mutants, since centrioles are absent from the mitotic apparatus. Cytological and hybridization studies of 230X affirm the nuclear basis of the mutation, and provide no support for the possible genetic autonomy of centrioles.

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Section: The Multilayered Structurementioning

confidence: 99%

Ultrastructural studies of mutant spermatozoids in ferns. I. The mature nonmotile spermatozoid of mutation 230X in Ceratopteris thalictroides(L.)Brongn

1979

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“…The spline microtubules shown in Fig. 21 bear densely stained protrusions that are similar to the "keels" or "longitudinal ridges" present on the spline microtubules of the MLS in Marchantia sperm (Carothers and Kreitner, 1967), wherein they were a consistent feature. In both Cephaleuros and Phycopeltis motile cells (Chapman, 1980;, the ridgedmicrotubules were rarely found, and in Trentepohlia motile cells (Graham and McBride, 1975)they were not observed.…”

Section: Discussion-mentioning

confidence: 76%

“…Although the lowest layer of the Vierergruppe (i.e. MLS) in Marchantia sperm Kreitner, 1967, 1968) is comprised of fine microtubules, the microtubules shown in Fig. 14-16 are clearly not comparable.…”

Section: Discussion-mentioning

confidence: 96%

Ultrastructure of Cephaleuros virescens (Chroolepidaceae; Chlorophyta). III. Zoospores

Chapman

1981

American Journal of Botany

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Transmission electron microscopic examination of Cephaleuros virescens Kunze growing on leaves of Camellia spp. and Magnolia grandiflora L. indicates that unreleased zoospores in mature zoosporangia are similar to those produced by the related genus Phvcopeltis epiphyton Millardet and unlike the quadriflagellate motile cells produced by taxa in other families of Chlorophyta. The zoospores bear four smooth isokont bilaterally "keeled" flagella containing typical "9 + 2" axonemes and lacking scales. Flagellar insertion is apical and the parallel basal bodies overlap laterally at two levels. A cross section through the four basal bodies shows a trapezoidal arrangement wherein the two upper (anterior) basal bodies are closer together than are the lower (posterior) two. Serial sections indicate that diagonally opposing upper and lower basal bodies anchor flagella which emerge from the same side of the apical papilla. Each of the four basal bodies is associated with a microtubular spline which extends beneath the plasmalemma to the posterior end of the zoospore. A distinct multilayered structure is associated with each of the lower basal bodies. A nucleus, mitochondria (two of which are closely associated with the nucleus and spline microtubules), a chloroplast, and cytoplasmic haematochrome droplets are present in each zoospore. Pyrenoids and eyespots are absent. Flagellar insertion is characterized by "reversed bilateral symmetry": and zoospores with both right-handed and left-handed arrangements are produced. The ultrastructure of the zoospores clearly indicates that: I) the mode of flagellar insertion: 2) morphology, number, and arrangement of multilayered structures, and 3) bilaterally keeled flagella are characteristic of the Chroolepidaceae.CEPHALEUROS VIRESCENS Kunze, a subaerial, subcuticular parasite of higher plants, has been more fully described in a previous report (Chapman, 1976b). Similarly, a report on the ultrastructure of biflagellate gametes (Chapman, 1980) presents additional introductory material and provides a basis for comparison between biflagellate and quadriflagellate cells.The description of Cephaleuros zoospores has been complicated by several factors. First, the quadriflagellate cells are more complex than the biflagellate gametes. Second, the condition of "reversed bilateral symmetry" documented and discussed in the gamete paper (Chapman, 1980) makes the interpretation of two-dimensional electron micrographs especially difficult because the micrographs, a priori, do not conform to a single cell model.

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“…The vertical lamellae and walls of S4 tubules are slightly thicker at 6.5-7 nm. The liverwort, Blasia pusilla, has a homogenous S2 at a time when spline elongation is probable (Carothers, 1973). 12-14 would be consistent with the appearance of structural units of similar size throughout the MLS.…”

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confidence: 72%

Studies of Spermatogenesis in the Hepaticae V. Blepharoplast Development in Marchantia polymorpha

Kreitner¹,

Carothers²

1976

American Journal of Botany

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Coaxial centrioles and a microtubule organizing center (MTOC) constitute each centrosome in spermatid mother cells of Marchantia polymorpha. During cell division the centrosome separates at its midregion and the two centrioles undergo a planar rotation that brings them to lie somewhat staggered and nearly parallel with their proximal ends embedded in osmiophilic granular material similar in appearance to that of the MTOC. Microtubules of the multilayered structure (MLS) arise in this material below the posterior centriole and parallel to its long axis. The rotation of centrioles and the initiation of S1 tubules below the posterior centriole determine polarity of the incipient blepharoplast. Lower MLS strata are formed under the anterior centriole by the compaction of granular, osmiophilic matrix. Formation and growth of S2 vertical lamellae occur at the left front edge of the MLS in association with MTOC‐like matrix localized near the cell membrane. The MLS enlarges to about 0.4 μm wide by 0.6 μm long and is ovoid in outline except for a short distal projection underlying the posterior centriole. Subsequently the lamellae are transformed into homogenous, osmiophilic matrix that contributes directly to the expansion of all MLS strata including microtubules. The stratum of lamellae is interpreted as a planar MTOC subject to morphogenetic control. Each of the four strata grows proximally while the tapering distal projection lengthens beneath the posterior basal body. Dense matrix above the MLS, apparently elaborated by the S2 layer, is organized into cartwheel and triplet components of the basal bodies’ proximal extensions. Organization of triplet tubules proceeds from proximal to distal toward preexisting triplets. Osmiophilic matrix contributes to the formation of microtubule keels and osmiophilic crests and may serve as a cementing material that stabilizes the spatial relationships of blepharoplast components. After full expansion of the MLS’ lower strata, the S2 layer is reorganized into lamellae. Flagellar growth in Marchantia is postulated to involve a process whereby subunits or their precursors are elaborated by the MLS, translocated to the distal end of the flagellum and incorporated into the axonemal tubules. When MLS microtubules elongate to form a long, narrow band, the distal half of the S2 layer is again in the osmiophilic matrix state.

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Studies of Spermatogenesis in the Hepaticae. Iv. On the Blepharoplast of Blasia

Cited by 38 publications

References 10 publications

Ultrastructural studies of mutant spermatozoids in ferns. I. The mature nonmotile spermatozoid of mutation 230X in Ceratopteris thalictroides(L.)Brongn

Ultrastructural studies of mutant spermatozoids in ferns. I. The mature nonmotile spermatozoid of mutation 230X in Ceratopteris thalictroides(L.)Brongn

Ultrastructure of Cephaleuros virescens (Chroolepidaceae; Chlorophyta). III. Zoospores

Studies of Spermatogenesis in the Hepaticae V. Blepharoplast Development in Marchantia polymorpha

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