“…Figure 4.Characteristic centriole assembly process in bryophytes and a marine protist. Two nascent centrioles (blue lines) assemble on a cartwheel stack (red lines), with their proximal ends facing each other, and then separate through binary fission [13,14]. Two models can be thought of for the assembly of the cartwheel stack, which serves as the scaffold for the bidirectional assembly of two centrioles.…”
The cartwheel is a subcentriolar structure consisting of a central hub and nine radially arranged spokes, located at the proximal end of the centriole. It appears at the initial stage of the centriole assembly process as the first ninefold symmetrical structure. The cartwheel was first described more than 50 years ago, but it is only recently that its pivotal role in establishing the ninefold symmetry of the centriole was demonstrated. Significant progress has since been made in understanding its fine structure and assembly mechanism. Most importantly, the central part of the cartwheel, from which the ninefold symmetry originates, is shown to form by self-association of nine dimers of the protein SAS-6. This finding, together with emerging data on other components of the cartwheel, has opened new avenues in centrosome biology.
“…Figure 4.Characteristic centriole assembly process in bryophytes and a marine protist. Two nascent centrioles (blue lines) assemble on a cartwheel stack (red lines), with their proximal ends facing each other, and then separate through binary fission [13,14]. Two models can be thought of for the assembly of the cartwheel stack, which serves as the scaffold for the bidirectional assembly of two centrioles.…”
The cartwheel is a subcentriolar structure consisting of a central hub and nine radially arranged spokes, located at the proximal end of the centriole. It appears at the initial stage of the centriole assembly process as the first ninefold symmetrical structure. The cartwheel was first described more than 50 years ago, but it is only recently that its pivotal role in establishing the ninefold symmetry of the centriole was demonstrated. Significant progress has since been made in understanding its fine structure and assembly mechanism. Most importantly, the central part of the cartwheel, from which the ninefold symmetry originates, is shown to form by self-association of nine dimers of the protein SAS-6. This finding, together with emerging data on other components of the cartwheel, has opened new avenues in centrosome biology.
“…Fig. 2 in Stubblefield and Brinkley, 1967;Brinkley and Stubblefield, 1970;Dippell, 1968;Grimes, 1973;Moser and Kreitner, 1970;Turner, 1968;Alvey, 1985;Tamm and Tamm, 19801 (cf. Fig.…”
Section: --mentioning
confidence: 99%
“…For example, it is well demonstrated that centrioles and basal bodies usually arise from existing centrioles or basal bodies. However, they can also form de novo [Turner, 1968;Manton et al, 1970;Moser and Kreitner, 1970;Perkins, 1970;Pickett-Heaps, 19731.…”
This paper suggests that the formation and structure of the microtubular skeleton of centrioles and basal bodies can be derived from the following simple geometric principle. A closed ring of nine microtubular initiation sites defines (1) a template for the packing of 18 additional microtubular initiation sites, and (2) the shape of nine rigid arms. Upon swivelling of each arm around a point located four initiation sites away on the initial ring, the array unfolds in a manner similar to the opening of an iris diaphragm. As a consequence, the curved shape of the microtubular triplet blades arises together with the clockwise rotational sense of the slanted blades of the centriole or basal body. The final diameter of the centriole (basal body) self-adjusts. Furthermore, the pitch of the triplet blades, the taper of centrioles and basal bodies, and the change of slant of the blades towards the distal end can be derived. In addition, the model points to a method of replication of pro-centrioles (pro-basal bodies). The hypothesis was tested by the fitting of electron microscopical cross sections of centrioles of 3T3 cells to the geometric shapes predicted by the model.
“…During the last century, an impressive record of the structural aspects of development during lower land plant spermiogenesis has been characterized. These studies established that in bryophytes, hornworts, and lycopods, a spermatocyte synthesizes a coaxially oriented pair of basal bodies within a centrosome-like amorphous mass (Kreitner and Carothers 1976;Moser and Kreitner 1969;Vaughn and Renzaglia 1998). In Isoetes, Equisetum, Psilotum, a number of pteridophytes, Ginkgo, and a number of cycads, the undifferentiated cell (generative cell in Ginkgo) condenses a nonmembrane-bound amorphous structure known as the blepharoplast (that is, eyelash), (Webber 1897).…”
Recent studies on a variety of organisms point to the ubiquity of RNA interference (RNAi) as a means to induce a gene-specific block to translation. RNAi has gained popularity in the last few years in the study of a number of problems in development. In this review, we highlight recent findings with RNAi using several different kinds of animals and fungi, and we show how these responses parallel cosuppression effects described in plants nearly a decade earlier. We then point to the efficacy of RNAi in studying minor and regulatory components of the plant cytoskeleton, and we highlight some recent studies using this approach with the water fern, Marsilea vestita.
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