The changes of nuclear position and distribution of circumferentially aligned cortical microtubules during the progression of cell cycle inAdiantum protonemata (original) (raw)
Related papers
Journal of Plant Physiology, 1996
Using indirect immunofluorescence, the system of radiating endoplasmic microtubules (REMTs) within intact cells of meristematic root tissues of maize has been examined throughout the cell cycle, paying special attention to its relationship with the pre-and post-mitotic nuclei with which it is associated. At early interphase, REMTs are not uniformly disposed around the nucleus but grow out from faint, though easily recognizable, perinuclear foci. During S and G2 phases, REMTs increase in number and have a close association with the assembly of the preprophase band (PPB) MT array. Later, when the cortical part of the PPB disintegrates, the REMTs align along the nuclear surface, predicting the long axis of the future mitotic spindle. In contrast to naturally wall-less cells, or to cells with perturbed cell walls, these pre-mitotic, as well as the subsequently formed post-mitotic cells display symmetrical rearrangements of their REMTs around the nuclear surface. Mitotic cells sectioned in the median plane show a symmetrical quadripolar MT organization which is obvious at all stages of mitosis. The symmetrical redistributions of the REMTs which occur during the cell cycle are perturbed, or even prevented, by treatments with chemical or with physical anti-MT agents. Nuclei of cells so treated accumulate REMTs, but fail to redistribute them symmetrically. As a result, the pre-and post-mitotic nuclei of root cells treated with anti-MT agents resemble, with respect to their REMTs, the corresponding nuclei of wall-less plant cells, or of cells which have perturbed cell walls. The dynamic REMTs which connect the pre-and post-mitotic nuclei with the cell periphery are suggested as being involved in sensing the position of dividing cells within the intact plant organ. This property of REMTs enables them to spatially control the sequential alignment of cell division planes of immobile walled plant cells which underlies the morphogenesis of higher plant organs.
Biology of the Cell, 1993
The duration of the different phases of the microtubule and chromosome cycles were estimated in the native diploid cell populations of Allitmt cepa L root meristems proliferating undisturbed, under steady state conditions, at the physiological temperature of 15°C. The cycles were coupled by considering their fitting in relation to the short process of nuclear envelope breakdown. In the cycle related to cytoplasmic division, the preprophase band which predicts the future position of the phragmoplast made its appearance, as a wide band, 16 min before the G, to prophase transition, ie it was only present during the final 5°70 of the total G_, timing (5 I1 30 min). The band became narrow only 6 min after prophase had started and it was present in this form for the remaining prophase time (2 I1 24 min). Its disappearance occurred strictly coinciding with nuclear envelope breakdown, at the end of prophase. No microtubules related to cytoplasmic division were apparent until 9 min after telophase had initiated. The two initial stages of phragmoplast formation which followed occupied, respectively, 27 min and 54.5 min of the 2-h long telophase. On the other hand, the third and last stage in phragmoplast formation covered both the final 35 min of mitosis and the 6 initial min of the G~ of the next interphase. A very short (less than 4 min) stage of microtubular nucleation around the nuclear envelope took place immediately afterwards, before the cortical array of microtubules appeared. The microtubule cycle related to nuclear division started with the apparent activation of the future spindle poles 7.4 min before prophase was over. The mitotic spindle developed in the 5.6 min long prometaphase. The spindle functioned in metaphase for the 42 rain it lasted, half spindles being separated for the 37 rain anaphase occupied in these cells. anti-tubulin / cell cycle / chromosomal cycle / microtubular cycle / onion / root meristems
Microtubules and their organizing centres in differentiating guard cells ofAdiantum capillus veneris
Protoplasma, 1983
The cortical cytoplasm of the young guard cells ofAdiantum capillus veneris is locally differentiated. At an early post-telophase stage, numerous microtubules diverge from the cytoplasm occupying the junctions of the midregion of the ventral wall with the periclinal ones, towards the periclinal and ventral wall faces as well as towards the inner cytoplasm. Microtubule-vesicle complexes (MVCs) are detected in these regions. Their appearance is accompanied by the initiation of local wall thickenings in the same areas. Afterwards, more distinct MVCs anchored to the plasmalemma were seen in the cortical cytoplasm of the periclinal walls, close to the growing thickenings, usually at a distance up to 3 ,am from them. Sometimes, they seemed to contain an electron dense substance in which the microtubules were embedded. Cortical microtubules converging from more than one direction terminate at the MVCs. Besides, the microtubule population lining the periclinal walls radiate from the regions where the above cytoplasmic formations are localized. The overlying cellulose microfibrils exhibit the same orientation. The vesicles localized at the MVCs appear to be of dictyosomal origin, very electron dense and react positively to periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) test. Another population of microtubules fan out from the MVCs, entering deeper into the cytoplasm. They become associated with the nucleus and mitochondria, and traverse the peridictyosomal cytoplasm. In some instances the nucleus formed a protrusion towards an MVC and appeared associated with it via microtubules which radiate from the MVC and flank the nuclear envelope.
Protoplasma, 1991
The interphase meristematic root cells ofAdiantum capillus venerispossess a well developed cytoskeleton of cortical microtubules (Mts), which disappear at prophase. The preprophase-prophase cells display a well organized preprophase microtubule band (PMB) and a perinuclear Mt system. The observations favour the suggestion that the cell edges included in the PMB cortical zone possess a Mt organizing capacity and thus play an important role in PMB formation. The perinuclear Mrs are probably organized on the nuclear surface. The preprophase-prophase nuclei often form protrusions towards the PMB cortical zone and the spindle poles, assuming a conical or rhomboid shape. Mts may be involved in this nuclear shaping. Reinstallation of cortical Mrs in dividing cells begins about the middle of cytokinesis with the reappearance of short Mts on the cell surface. When cytokinesis terminates, numerous Mts line the postcytokinetic daughter wall. Many of them converge or form clusters in the cytoplasm occupying the junctions of the new and the old walls. In the examined fern, the cortical Mt arrays seem to be initiated in the cortex of post-cytokinetic root cells. A transitory radial perinuclear Mt array, comparable to that found in post-telophase root cells of flowering plants, was not observed in A. capillus veneris.
Cytoskeletal pattern changes during branch formation in a centrifuged Adiantum protonema
Journal of Plant Research, 1998
A protonemal branch was induced on a side wall of a fern filamentous protonema by cell centrifugation and subsequent polarized-red light irradiation as described in a previous paper (Wada 1995, J. Plant Res. 108: 501–509). Changes in microtubule (MT) and microfilament (MF) patters during the branch development were observed under fluorescence microscopy. A ring-like band of cortical MTs (MT-ring) and MFs similar to a preprophase band or a subapical ring structure (Murataet al. 1987) appeared transiently at the future branching site before cell swelling, the first visible step of branch formation. At this stage, the nucleus was located far from the branching site and the MT-ring appeared to be connected to the nucleus by endoplasmic MFs as well as with endoplasmic MTs. The MT-ring disappeared when cell wall swelling occurred. When the cell wall swelling began, a fan-like pattern of cortical MTs emanating from the new growing tip was established and the MTs reached the opposite flank of the protonema. When a new branch started to elongate and the nucleus moved into the branch, a faint subapical ring of MTs appeared at the subapical part of the new branch. Strands of MTs and MFs emanating from the nuclear front end reached a part of the subapical ring.
Nuclear gamma-Tubulin during Acentriolar Plant Mitosis
THE PLANT CELL ONLINE, 2000
Neither the molecular mechanism by which plant microtubules nucleate in the cytoplasm nor the organization of plant mitotic spindles, which lack centrosomes, is well understood. Here, using immunolocalization and cell fractionation techniques, we provide evidence that ␥-tubulin, a universal component of microtubule organizing centers, is present in both the cytoplasm and the nucleus of plant cells. The amount of ␥-tubulin in nuclei increased during the G 2 phase, when cells are synchronized or sorted for particular phases of the cell cycle. ␥-Tubulin appeared on prekinetochores before preprophase arrest caused by inhibition of the cyclin-dependent kinase and before prekinetochore labeling of the mitosis-specific phosphoepitope MPM2. The association of nuclear ␥-tubulin with chromatin displayed moderately strong affinity, as shown by its release after DNase treatment and by using extraction experiments. Subcellular compartmentalization of ␥-tubulin might be an important factor in the organization of plant-specific microtubule arrays and acentriolar mitotic spindles. z
Planta, 1988
We have studied the timing of preprophase band (PPB) development in the division cycle of onion ( A l l i u m c e p a L.) root-tip cells by combinations of immunofluorescence microscopy of microtubules, microspectrophotometry of nuclear DNA, and autoradiography of [3H]thymidine incorporation during pulse-chase experiments. In normally grown onion root tips, every cell with a PPB had the G2 level of nuclear DNA. Some were in interphase, prior to chromatin condensation, and some had varying degrees of chromatin condensation, up to the stage of prophase at which the PPB-prophase spindle transition occurs. In addition, autoradiography showed that PPBs can be formed in cells which have just finished their S phase, and microspectrophotometry enabled us to detect a population of cells in G2 which had no PPBs, these presumably including cells which had left the division cycle. The effects of inhibitors of D N A synthesis showed that the formation of PPBs is not fully coupled to events of the nuclear cycle. Although the mitotic index decreased 6-10-fold to less than 0.5% when roots were kept in 20 lag" ml-1 aphidicolin for more than 8 h, the percentage of cells containing PPBs did not decrease in proportion: the number of cells in interphase with PPBs increased while the number in prophase decreased. Almost the same phenomena were observed in the presence of 100 lag.ml-1 5-aminouracil and 40 lag" ml-~ hydroxyurea. In controls, all cells with APC = aphidicolin; 5-AU = 5-aminouraeil; DAPI = 4',6-diamidino-2-phenylindole; H U = hydroxyurea; MI = mitotic index; MT = mierotubule; PMSF = phenylmethylsulfonyl fluoride; PPB=preprophase band; %PPB=perccntage of cells with PPBs PPBs were in G2 or prophase, but in the presence of aphidicolin, 5-aminouracil or hydroxyurea, some of the interphase cells with PPBs were in the S phase or even in the G1 phase. We conclude that PPB formation normally occurs in G2 (in at least some cases very early in G2) and that this timing can be experimentally uncoupled from the timing of D N A duplication in the cell-division cycle. The result accords with other evidence indicating that the cytoplasmic events of cytokinesis are controlled in parallel to the nuclear cycle, rather than in an obligatorily coupled sequence.