Study of mitosis in root-tip cells ofTriticum turgidum treated with the DNA-intercalating agent ethidium bromide

Abstract

This work examines mitosis in root-tip cells of Triticum turgidurn treated with the RNA synthesis inhibitor ethidium bromide, using tubulin immunolabeling and electron microscopy. The following aberrations were observed in ethidium bromideaffected cells: (1) incomplete chromatin condensation and nuclearenvelope breakdown; (2) delay of preprophase microtubule band maturation; (3) preprophase microtubule band assembly in cells displaying an interphase appearance of the nucleus; (4) prevention of the prophase spindle formation, caused by inhibition of perinuclear microtubule (Mt) formation and/or inability of the perinuclear Mts to assume bipolarity; (5) organization of an atypical metaphase spindle which is unable to arrange the chromosomes on the equatorial plane; (6) formation of an atypical "perinuclear metaphase spindle" in cells in which nuclear-envelope breakdown has been almost completely inhibited; (7) inhibition of the anaphase spindle formation as well as of anaphase chromosome movement; (8) disorganization of the atypical mitotic spindle during transition from mitosis to cytokinesis. The observations favor the following hypotheses. Nucleation of prophase spindle Mts is related to the mechanism that causes nuclear-envelope breakdown. The mitotic poles lack Mtnucleating and -organizing properties, and their function does not account for prophase and metaphase spindle assembly. The organization of the prophase spindle is not a prerequisite for the formation of the metaphase spindle; the metaphase spindle seems to be formed de novo by Mts nucleated on the nuclear envelope and/or in the immediate vicinity of chromosomes.

Hyperosmotic Stress Induces Formation of Tubulin Macrotubules in Root-Tip Cells of Triticum turgidum: Their Probable Involvement in Protoplast Volume Control

“…Mt organization in meristematic root-tip cells of T. turgidum has been previously described (Zachariadis et al 2000, Frantzios et al 2000, Frantzios et al 2001 and is similar to that described in root-tip cells of other angiosperms. Interphase cortical Mt systems, preprophase Mt bands (PPBs), mitotic spindles, interzonal Mt systems, as well as phragmoplasts at different stages of development were observed in the meristematic cells examined (Fig.…”

Cytoskeletal asymmetry in Zea mays subsidiary cell mother cells: A monopolar prophase microtubule half‐spindle anchors the nucleus to its polar position

“…According to the above, the organization of a bipolar prophase microtubule spindle is not a prerequisite for the formation of the metaphase microtubule spindle. The latter seems to be organized de novo during prometaphase/metaphase, as has also been shown in other angiosperms [Zachariadis et al, 2000[Zachariadis et al, , 2004Chan et al, 2005].…”

A role for katanin in plant cell division: Microtubule organization in dividing root cells of fra2 and lue1Arabidopsis thaliana mutants

“…Bipolar metaphase spindles have also been found to organize in cells that possessed faulty prophase spindles, due to preprophase band defects [Camilleri et al, 2002;Marcus et al, 2003;Chan et al, 2005], but also in cells with monopolar prophase spindles [Panteris et al, 2006]. Zachariadis et al [2000Zachariadis et al [ , 2004 supported that in angiosperms the metaphase spindle may not emanate from the prophase spindle. In addition, according to Lloyd and Chan [2006], a typical bipolar metaphase spindle may be assembled without the prior presence of a bipolar ''capped'' prophase spindle: A process similar to the chromosome-driven spindle organization of acentrosomal animal cells may occur in plant cells, resulting in typical metaphase spindle formation without a prior bipolar prophase spindle.…”