Centriole Replication

Abstract

Sperm formation was studied in the fern, Marsilea, and the cycad, Zamia, with particular cmphasis on thc ccntrioles. In Marsilea, the maturc spcrm posscsses over 100 flagella, the basal bodies of which have the typical cylindrical structure of centriolcs. Earlier obscrvations by light microscopy suggcsted that these centrioles arise by fragmentation of a body known as the blepharoplast. In the youngest spermatids the blepharoplast is a hollow sphere approximately 0.8 tt in diameter. Its wall consists of closely packed immature ccntriolcs, or proccntriolcs. Thc procentrioles arc short cylinders which progressively lengthen during differentiation of the spermatid. At the same time thcy migrate to the surface of thc ccll, where each of thcm puts out a i]agcllum. A blepharoplast is found at cach pole of thc spindle during the last antheridial mitosis, and two blcpharoplasts are found in the cytoplasm before this mitosis. Blepharoplasts arc also found in the prcccding cell generation, but their ultimatc origin is obscure. Before thc last mitosis the blepharoplasts are solid, consisting of a clustcr of radially arranged tubulcs which bear some structural similarity to centrioles. In Zamia, similar stages are found during sperm formation, although here thc number of flagella on each sperm is close to 20,000 and thc blepharoplast measures about l0 tt in diameter. These observations arc discussed in relation to theories of ccntriolc replication.

Centriole/basal body morphogenesis and migration during ciliogenesis in animal cells

“…Several serine/threonine kinases are implicated in the process, including Polo-like and Aurora kinases (Berdnik and Knoblich, 2002;Hannak et al, 2001;Lane and Nigg, 1996). A procentriole (Andre and Bernhard, 1964;Gall, 1961;Mizukami and Gall, 1966;Renaud and Swift, 1964) forms from the side of each centriole and elongates throughout S phase so that the cell possesses two pairs of centrioles as it Fig. 1 and ❶) lacking central pair microtubules, which is lost as the cell re-enters the cell cycle.…”

Evolution and persistence of the cilium

“…In multiciliated cells of plants including ferns [Mizukami and Gall, 1966] and cycads, and in animals, centrioles arise en masse from a fibrogranular center [Dirksen and Crocker, 1966;Dirksen, 1991] reminiscent of a viral replication factory [Novoa et al, 2005]. Similarly, protistan anarchic fields first contain amorphous material from which multiple basal bodies self assemble.…”

Spermidine Is a Morphogenetic Determinant for Cell Fate Specification in the Male Gametophyte of the Water FernMarsilea vestita

“…An important facet of spermatid development is the de novo formation of basal bodies from a particle known as a blepharoplast, which arises during the last mitotic division cycle and then differentiates to produce 140 basal bodies in each spermatid (Mizukami and Gall, 1966;Hepler, 1976). Each spermatid then forms an elaborate cytoskeleton.…”

“…The top-most stratum of the MLS is the microtubule ribbon, which comprises approximately 40 cross-linked microtubules and extends along the length of the elongated and coiled nucleus (Myles and Hepler, 1977). The microtubule ribbon has long been thought to be responsible for directing the spiral elongation pattern of the cell body and the nucleus (Mizukami and Gall, 1966;Myles and Hepler, 1977). The elongation of the gamete nucleus is accompanied by the condensation of the chromatin.…”