Cellular Polarity in Ciliates: Persistence of Global Polarity in a disorganized Mutant of Tetrahymena thermophila That Disrupts Cytoskeletal Organization

Abstract

Much of the cell surface on the ciliate Tetrahymena thermophila is covered by a polarized lattice of cytoskeletal structures that are associated with basal bodies of the ciliary rows. Unique structural landmarks, including an oral apparatus and contractile vacuole pores, develop before cell division in localized domains located, respectively, posterior and anterior to the transverse fission zone. All of these structures can be visualized by specific monoclonal antibodies. A single-locus recessive mutation, disorganized-A (disA), primarily affects the striated rootlets of the ciliary-row basal bodies and brings about a severe disorganization in the positioning and orientation of these basal bodies and associated cytoskeletal elements. Nonetheless, the new oral apparatus, contractile vacuole pores, and other unique structures appeared at or near their normal sites along the anteroposterior axis of disA cells, indicating that the positioning of these localized structures is not dependent on the integrity of the ciliary rows. Abnormalities were present in the details of construction of some of the localized structures and in aspects of cell shape that may be influenced by these details. In the main, however, analysis of disA mutant cells indicates that intracellular domains near the cell poles develop independently of the vectorial polarity of the ciliary rows.

What Do Genic Mutations Tell Us about the Structural Patterning of a Complex Single-Celled Organism?

“…It was expressed moderately at normal growth temperatures and more highly at 39°C; it brought about a disorganization of the arrangement and spatial orientation of ciliary units (Fig. 5B), without severe disruption of the internal organization of each individual unit (6,79). Remarkably, not only could disorganized mutant cells continue to grow and divide for some time even at restrictive temperatures; they could also develop normal new OAs at their normal locations ( Fig.…”

“…Remarkably, not only could disorganized mutant cells continue to grow and divide for some time even at restrictive temperatures; they could also develop normal new OAs at their normal locations ( Fig. 5B) and place the CVPs at correct intracellular latitudes and approximately correct longitudes (79). This, therefore, clearly demonstrates the dissociability of the large-scale patterning of the major cortical landmarks and of the distinctive mechanisms that are responsible for the development of oral structures (39,115) from the spatial order of the ciliary rows (reviewed in reference 41).…”

“…The conclusion that the plane of bisection of the cell does not depend on the geometry of the ciliary row was demonstrated more clearly by cells expressing one of several nonallelic disorganized mutations. The most highly expressed and most thoroughly investigated of these is the disA-1 mutation (6,35,79). This mutation is located on chromosome 5 (15).…”

The Toxoplasma gondii centrosome is the platform for internal daughter budding as revealed by a Nek1 kinase mutant

“…Cleared parasite lysates representing 20 million parasites separated by SDS-PAGE gels and transferred to nitrocellulose membrane. The blots were probed by anti-TgNek1-2 (1:1000) and atubulin 12G10 (1:500) [Hybridoma Bank, University of Iowa (Jerka-Dziadosz et al, 1995)], goat anti-guinea pig IgG-HRP sc-2438 (1:3000; Santa Cruz) and goat anti-mouse HRP (1:10,000; Invitrogen).…”

Choosing sides – asymmetric centriole and basal body assembly

“…In Tetrahymena this is the kinetodesmal fiber, in Paramecium the striated rootlet, and in Chlamydomonas the striated microtubuleassociated fiber (Fig. 2) (Allen, 1969;Holmes and Dutcher, 1989;Iftode and Fleury-Aubusson, 2003;Jerka-Dziadosz et al, 1995;Lechtreck and Melkonian, 1991;Munn, 1970;Sperling et al, 1991). Striated fibers extend from a defined triplet microtubule site on the basal body at the base of mature basal bodies and, as their name suggests, are composed of fibers with striations of ,30-nm periodicity.…”