Patterns of cortical and perinuclear microtubule organization in meristematic root cells ofAdiantum capillus veneris (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.
Protoplasma, 1995
Taxol stabilizes phragmoplast microtubules (Mts) in cytokinetic root cells of Triticum, causing a delay in the rate of cytokinesis. As a result, the daughter nuclei acquire interphase appearance in mid-to late-cytokinetic taxoi-affected cells much earlier than in control cells. Cortical Mts in such cells appear directly in the cell cortex, without the prior organization of a radial perinuclear Mt array as in control ceils. These observations suggest that: (a) Whether perinuclear Mt assembly occurs or not in post-telophase cells is a matter of timing between the nuclear cycle and cytokinesis. (b) Mt organizing activity on the daughter nuclei surface is temporal. (c) Cortical Mts can be in situ assembled in the cortex of post-telophase cells of flowering plants without any participation of perinuclear Mrs. Abbreviations: Mt microtubules; MTOC microtubule organizing centre; DMSO dimethyl sulfoxide; EM electron microscope.
Protoplasma, 1993
Mesophylt c, ells (MCs) of Adiantum capillus veneris are elongated and highly asymmetric, bearing several lateral branches and forming a meshwork resembling aerenchyma. Young MCs are poIyhedral and display oppositely arranged walls and transverse cortical microtubules (Mts). Their morphogenesis is accomplished in three stages. At first they become cylindrical. Intercellular space (IS) canals, containing PAS-positive naaterial, open through their junctions and expand laterally, During the second stage the cortical Mts form a reticulum of bundles, externally of which an identical reticulum of wall thickenings, containing bundles of parallel cellulose microfibrits, emerges. MCs do not grow in girth in the regions of wall thickenings, where constrictions form and new ISs open, Thus, MCs obtain a multi-lobed form. At the third morphogenetic stage MCs display a multi-axial growth. During this process, additional Mt rings are assembled at the base of ceil lobes accompanied by similarly organized wall thickenings-cellulose microfibrils. Consequently, cell lobes elongate to form lateral branches, where MCs attach one another, while the IS labyrinth broadens considerably. Colchicine treatment, destroying Mts, inhibits MC morphogenesis and the concomitant IS expansion, but does not affect IS canal formation. These observations show that: (a) MC morphogenesis in A. capillus venerisis an impressive phenomenon accurately controlled by highly organized cortical Mt systems, (b) The disposition of Mt bundles between neighbouring MCs is highly coordinated. (c) The perinuclear cytoplasm does not appear to be involved in cortical Mt formation. Cortical sites seem to participate in Mt bundling. (d) Although extensive IS canals open before Mt bundling, the Mtdependent MC morphogenesis contributes in IS formation. Abbreviations: EM electron microscopy; ER endoplasmic reticulum; IS intercelhilar space; MC mesophyll cell; MSB microtubule stabilizing buffer; Mt microtubule; PBS phosphate buffered saline.
In the presence of cytokinin, undetermined side branch initials of the moss, Physcomitrella patens, are induced to form buds and then leafy shoots rather than to develop as tip-growing filaments. This represents a transition between the two modes of plant cell expansion-tip growth and uniform intercalary growth. The organization of microtubules in filaments is different from that in leafy shoots and can be traced back to the influence of phytohormones on side branch initials. Microtubules either focus at a particular region (as in tip-growing cells) or in the presence of high levels of cytokinin form swollen bud initials in which microtubules are more diffusely organized. Higher levels of cytokinin are capable of destabilizing tip microtubules in caulonemal filaments. Although caulonemata are not normally target cells, this implies that cytokinin may exert its morphogenetic effects by altering microtubule organization. IR tip-growing filaments, interphase microtubules trace a meandering course through the cytoplasm towards the tip and are not for the main part associated with the plasma membrane as are cortical arrays. There is no pre-prophase band of microtubules to indicate the future division plane, even though the oblique division plane is known to be precisely controlled relative to environmental factors. This microtubule cycle contrasts with cells of the leafy shoots that develop from buds: in these, the interphase array is cortical, consisting of flat-pitched microtubular helices that do not focus upon a growing tip. It is now shown that pre-prophase bands occur at this stage. The absence of bands does not readily correlate with imprecise control of the division plane. Instead, it is proposed that the ability to form pre-prophase bands depends upon the arrangement of microtubules in the preceding interphase array. Ways in which bands might be formed are discussed and the generality of these ideas is tested by observations on higher plant cells.
1987
A prominent feature of tip growth in filamentous plant cells is that the nucleus often migrates in step with the tip as it extends. We have studied this longrecognized but unexplained relationship in root hairs of the legume Viciu hirsutu by a variety of microscopic techniques. Using rhodaminyl lysine phallotoxin, and antitubulin antibodies, root hairs are shown to contain axial bundles of F-actin and a complex microtubular system. To the basal side of the nucleus the microtubules are cortical and net axial but in the region between nucleus and tip the arrangement is more complicated. Electron microscopic thin sections demonstrate that internal bundles of microtubles exist in addition to the plasma membrane-associated kind. Computerized deblurring of through-focal series of antitubulin stained hairs clarifies the three-dimensional organization: bundles of endoplasmic microtubules progress from the nuclear region toward the apical dome where they can be seen to fountain out upon the cortex. The relationship between nucleus and tip can be uncoupled with antiniicrotubule herbicides. Time lapse video microscopy shows that these agents cause the nucleus to migrate toward the base. This contrary migration can be inhibited by adding cytochalasin D, which fragments the F-actin bundles. It is concluded that microtubules connect the nucleus to the tip but that F-actin is involved in basipetal migration as is known to occur when symbiotic bacteria uncouple the nucleus from the tip.
The Journal of Cell Biology, 1981
Microtubules participate as morphogenetic tools in two basic processes by which plants develop their characteristic forms : (a) production of new cells in specific sites and with specific initial shapes by partitioning of parental cells, and (b) further shaping of the progeny during their expansion and differentiation . In respect of (a), microtubules are present in the mitotic spindle, where they develop in the absence of centrioles (14). Immediately before the division cycle they are deposited as a transitory "pre-prophase band" (PPB) , which in its positioning predicts the site and plane of the future cytokinesis. At telophase another microtubule system contributes to the organization of the phragmoplast, which contains the new partitioning wall, or cell plate. In respect of(b), there are many instances of congruence between the orientation of microtubules in the cell cortex during interphase ("interphase cortical arrays") and the orientation of currently deposited microfibrils of cell wall material (see 12 and 15 for recent summaries) . The inference is that the cell exerts geometrical control over its expansion by setting up specifically oriented microtubule arrays. These in turn guide wall deposition, thereby regulating the mechanical properties of the wall and determining its spatial reaction to the turgor forces that drive cell expansion.
Microtubule and actin filament organization during stomatal morphogenesis in the fernAsplenium nidus
Protoplasma, 1997
The newly-formed guard cell mother cells (GMCs) of Asplenium nidus are small, lens-shaped and are formed by one or two asymmetrical divisions. Their growth axis is parallel to the plane of their future division, a process during which the internal periclinal wall (1PW) is detached from the partner wall of the underlying cell(s). This oriented GMC expansion occurs transversely to a microfibril bundle, which is deposited externally to a U-like microtubule (Mt) bundle and a co-localized actin filament (At) bundle. They line the IPW and the major part of the anticlinal walls. The deposition of the microfibril bundle is followed by the slight constriction of the internal part of the GMCs and the broadening of the substomatal cavity. The IPW forms a distinct bulging distal to the neighbouring leaf margin, as well as a less defined proximal one. During the IPW bulging, the Mts and Afs under the external perielinal wall (EPW) attain a radial organization. This is followed by thinning of the central EPW region, which becomes impregnated with a callose-like glucan. The rest of the EPW becomes unequally thickened. The disintegration of the U-like Mt bundle is succeeded by the organization of radial Mt and Af arrays under the IPW. The radial Mt systems, controlling the alignment of the newly-deposited microfibrils, allow the GMC to assume a round paradermal profile. The GMCs form a preprophase Mt band (PPB) perpendicular to the interphase U-like Mt bundle. The anticlinal PPB portions appear first and those lining the periclinal walls later. The cytoplasm adjacent to the latter walls retain the radial Mt systems during early preprophase, simultaneously with the anticlinal PPB portions. The observations suggest that the GMCs of the fern A. nidus obtain a unique form, as a result of a particular polarity established in the cortical cytoplasm of the periclinal walls, in which Mts and Afs appear involved. This polarity persists in cell division and is "inherited" to guard cells (GCs). It provides primary morphogenetic information not only to GMCs but also to GCs.
The organization of F-actin in root tip cells ofAdiantum capillus veneris throughout the cell cycle
Protoplasma, 1992
The patterns of F-actin in relation to microtubule (Mr) organization in dividing root tip cells of Adiantum capillus veneris were studied with rhodamine-phalloidin (RP) labelling and tubulin immunofluorescence. Interphase cells display a well organized network of cortical/subcortical, endoplasmie and perinuclear actin illaments (AFs), not particularly related to the interphase Mt arrays. The cortical AFs seem to persist during the cell cycle while the large subcortical AF bundles disappear by preprophase/prophase and reappear after cytokinesis is completed. In some but not all of the preprophase cells the cortical AFs tend to form a band (AF-PPB) coincident with the preprophase band of Mrs (Mt-PPB), In rectaphase and anaphase cells AFs are localized in the cell cortex, around the spindle and inside it coincidently with kinetochore Mt bundles. During cytokinesis AFs are consistently found in the phragrnoplast. In oryzalin treated cells neither Mt-PPBs, spindles and phragmoptasts exist, nor such F-actin structures can be observed. In cells recovering from oryzalin, AF-PPBs, "AF kinetochore bundles" and "AF phragmoplasts" reform. They show the same pattern ~4th the reinstating respective Mt arrays, tn contrast, in cells treated with cytochalasin B (CB), AFs disappear but all categories of Mt arrays form normally. These observations show that F-actin organization in root tip cells of A. capillus veneris differs from that of root tip cells of flowering plants examined so far. In addition, Mts seem to be crucial for Factin organization as far as it concerns the PPB, the mitotic spindle, and the phragmoplast.
PLANT PHYSIOLOGY, 2002
To investigate the configuration and function of microtubules (MTs) in tip-growing Medicago truncatula root hairs, we used immunocytochemistry or in vivo decoration by a GFP linked to a MT-binding domain. The two approaches gave similar results and allowed the study of MTs during hair development. Cortical MTs (CMTs) are present in all developmental stages. During the transition from bulge to a tip-growing root hair, endoplasmic MTs (EMTs) appear at the tip of the young hair and remain there until growth arrest. EMTs are a specific feature of tip-growing hairs, forming a three-dimensional array throughout the subapical cytoplasmic dense region. During growth arrest, EMTs, together with the subapical cytoplasmic dense region, progressively disappear, whereas CMTs extend further toward the tip. In full-grown root hairs, CMTs, the only remaining population of MTs, converge at the tip and their density decreases over time. Upon treatment of growing hairs with 1 m oryzalin, EMTs disappear, but CMTs remain present. The subapical cytoplasmic dense region becomes very short, the distance nucleus tip increases, growth slows down, and the nucleus still follows the advancing tip, though at a much larger distance. Taxol has no effect on the cytoarchitecture of growing hairs; the subapical cytoplasmic dense region remains intact, the nucleus keeps its distance from the tip, but growth rate drops to the same extent as in hairs treated with 1 m oryzalin. The role of EMTs in growing root hairs is discussed. ; fax 31-317-485005.