共查询到20条相似文献,搜索用时 15 毫秒
1.
Franz Grolig 《Planta》1997,204(1):54-63
The contribution of microtubules and microfilaments to the cytomechanics of transverse nuclear centering were investigated
in the charophycean green alga Spirogyracrassa (Zygnematales). Cytoplasmic strands of enhanced rigidity and fasciate appearance radiate from the rim of the lenticular nucleus
through the vacuole, frequently split once or twice and are attached to the helical chloroplast bands in the peripheral cytoplasm.
The nucleus is encased in tubulin and a web of F-actin. Bundles of microtubules, emerging from the nuclear rim, are organized
into dividing fascicles within the strands and reach to the inner surface of the chloroplast envelope. Organelles are translocated
in both directions along similarly arranged fascicles of microfilament bundles which extend from the nucleus to the peripheral
actin cytoskeleton. Application of microtubule- and/or microfilament-depolymerizing drugs affected the position of the nucleus
only slowly, but in distinct ways. The differential effects suggest that nuclear centering depends on the tensional integrity
of the perinuclear scaffold, with microfilaments conveying tension along stabilized microtubules and the actin cytoskeleton
integrating the translocation forces generated within the scaffold.
Received: 9 December 1996 / Accepted: 29 April 1997 相似文献
2.
Disruption of cellulose synthesis by isoxaben causes tip swelling and disorganizes cortical microtubules in elongating conifer pollen tubes 总被引:8,自引:0,他引:8
Summary. In elongating pollen tubes of the conifer Picea abies (Norway spruce), microtubules form a radial array beneath the plasma membrane only at the elongating tip and an array parallel
with elongation throughout the tube. Tips specifically swell following microtubule disruption. Here we test whether these
radial microtubules coordinate cell wall deposition and maintain tip integrity as tubes elongate. Control pollen tubes contain
cellulose throughout the walls, including the tip. Pollen tubes grown in the presence of isoxaben, which disrupts cellulose
synthesis, are significantly shorter with a decrease in cellulose throughout the walls. Isoxaben also significantly increases
the frequency of tip swelling, with no effect on tube width outside of the swollen tip. The decrease in cellulose is more
pronounced in pollen tubes with swollen tips. The effects of isoxaben are reversible. Following isoxaben treatment, the radial
array of microtubules persists beneath the plasma membrane of nonswollen tips, while this array is specifically disrupted
in swollen tips. Microtubules instead form a random network throughout the tip. Growth in these pollen tubes is turgor driven,
but the morphological changes due to isoxaben are not just the result of weakened cell walls since pollen tubes grown in hypoosmotic
media are not significantly shorter but do have swollen tips and tubes are wider along their entire length. We conclude that
the radial microtubules in the tip do maintain tip integrity and that the specific inhibition of cellulose microfibril deposition
leads to the disorganization of these microtubules. This supports the emerging model that there is bidirectional communication
across the plasma membrane between cortical microtubules and cellulose microfibrils.
Received January 15, 2002; accepted August 3, 2002; published online March 11, 2003 相似文献
3.
The timing of cell differentiation can be controlled both by cell-intrinsic mechanisms and by cell-extrinsic signals. Oligodendrocyte
type-2 astrocyte progenitor cells are known to be the precursor cells that give rise to oligodendrocytes. When stimulated
to divide by purifed cortical astrocytes or by platelet-derived growth factor, these progenitor cells generate oligodendrocytes
in vitro with a timing like that observed in vivo. The most widely accepted model of this process assumes a cell-intrinsic biological clock that resides in the progenitor
cell. The intrinsic clock model originally proposed in 1986 remains as the dominant theoretical concept for the analysis of
timed differentiation in this cell lineage. However, the results of a recent experimental study (Ibarrola et al., Developmental
Biology, vol. 180, 1–21, 1996) are most consistent with the hypothesis that the propensity of a clone of dividing O-2A progenitor
cells initially to generate at least one oligodendrocyte may be regulated by cell-intrinsic mechanisms, but that environmental
signals regulate the extent of further oligodendrocyte generation. We propose a stochastic model of cell differentiation in
culture to accommodate the most recent experimental findings. Our model is an age-dependent branching stochastic process with
two types of cells. The model makes it possible to derive analytical expressions for the expected number of progenitor cells
and of oligodendrocytes as functions of time. The model parameters were estimated by fitting these functions through data
on the average (sample mean) number of both types of cells per colony at different time intervals from start of experiment.
Using this method we provide a biologically meaningful interpretation of the observed pattern of oligodendrocyte generation
in vitro and its modification in the presence of thyroid hormone.
Received: 18 April 1997 / Revised version: 30 November 1997 相似文献
4.
Cytoskeletal alterations in interphase cells of the green alga Spirogyra decimina in response to heavy metals exposure: I. The effect of cadmium 总被引:1,自引:0,他引:1
Summary. The aim of the study was to elucidate the effect of cadmium ions on the arrangement of the actin and tubulin cytoskeleton,
as well as the relationships between cytoskeletal changes and growth processes in the green filamentous alga Spirogyra decimina. Batch cultures of algae were carried out under defined conditions in the presence of various cadmium concentrations. In
control cells, the cytoskeleton appeared to be a transversely oriented pattern of both microtubules and actin filaments of
various thickness in the cell cortex; colocalization of cortical microtubules and actin filaments was apparent. Microtubules
were very sensitive to the presence of cadmium ions. Depending on the cadmium concentration and the time of exposure, microtubules
disintegrated into short rod-shaped fragments or they completely disappeared. A steep increase in cell width and a decrease
in growth rate accompanied (and probably ensued) a very rapid disintegration of microtubules. Actin filaments were more stable
because they were disturbed several hours later than microtubules at any cadmium concentration used. When cadmium ions were
washed out, the actin cytoskeleton was rebuilt even in cells in which actin filaments were completely disintegrated at higher
cadmium concentrations (40 or 100 μM). The much more sensitive microtubules were regenerated after treatment with lower cadmium
concentrations (10 or 15 μM) only.
Correspondence and reprints: Centre of Phycology, Institute of Botany, Academy of Sciences of the Czech Republic, Dukelská
135, 379 82 Třeboň, Czech Republic. 相似文献
5.
Summary. We report that a novel substance named dictyopyrone C (DPC) has remarkable effects on growth and differentiation of Dictyostelium discoideum Ax-2 cells, in a dose-dependent manner. In the presence of 3–15 μM DPC, differentiation of starving Ax-2 (clone MS) cells
was greatly enhanced in submerged culture, when vegetative MS cells were harvested at the mid-late-exponential growth phase
(>3 × 106 cells per ml) and starved. In contrast, DPC above 30 μM markedly impaired the progression of differentiation including cell
aggregation, most of starved cells being round after 3–4 h of DPC application and then lysed during further incubation. In
the presence of 30 μM DPC however, MS cells that had been harvested at the early exponential growth phase (<5 × 105 cells per ml) and starved became neither round nor lysed and exhibited rather enhanced differentiation. Essentially the same
results were obtained in cultures of starved cells on nonnutrient agar. With respect to the DPC effect on MS cells growing
in axenic medium, cell lysis and growth inhibition by DPC at concentrations higher than 15 μM were realized in the mid-late-exponential-growth-phase
cells (>3 × 106 cells per ml) but not in the early-exponential-growth-phase cells (<5 × 105 cells per ml). Moreover, analysis using synchronized MS cells has demonstrated that the DPC effect changes in a cell-cycle-dependent
manner. In contrast to such unique DPC actions, the pyrone ring of DPC had no effects on growth and differentiation within
the range of 3–120 μM tested. These findings strongly suggested the importance of the combined structure of the pyrone ring
and the linear carbon chain in revelation of the DPC activities.
Received August 5, 2002; accepted November 11, 2002; published online April 8, 2003
RID="*"
ID="*" Correspondence and reprints: Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences,
Tohoku University, Aoba, Sendai 980-8578, Japan. E-mail: ymaeda@mail.cc.tohoku.ac.jp 相似文献
6.
S. Siljak-Yakovlev S. Peccenini E. Muratovic V. Zoldos O. Robin J. Vallès 《Plant Systematics and Evolution》2003,236(3-4):165-173
Three related and taxonomically close species of the genus Lilium (L. pyrenaicum Gouan, L. pomponium L. and L. carniolicum Bernh.), all of them with 2n=24 chromosomes, have been studied for chromosomal differentiation, using fluorochrome banding
and fluorescence in situhybridization (FISH), and for genome size and GC percentage using flow cytometry. The total DNA content of L. pomponium (2C=70.26 pg) was about 5% higher than that of L. pyrenaicum (2C=67.74) and L. carniolicum (2C=67.37 pg), while GC percentage was higher in this last species (36.60%) than in L. pomponium (35.56%) and lower than in L. pyrenaicum (37.92%). Silver staining, fluorochrome banding with chromomycin A3 (CMA) and fluorescence in situ hybridization (FISH) clearly pointed out the number of nucleoli, the number and position of GC-rich bands and the number
and location of rDNA sites thus permitting distinction of the three species at chromosomal level. Two families of ribosomal
genes, 18S-5.8S-26S (18S) and 5S rRNA genes, were separated onto different pairs in chromosome complements of examined species.
Chromosome regions containing both kinds of rRNA genes were also GC-rich regions. The results revealed a clear interspecific
differentiation at the chromosomal level and permitted the discussion about relationships among the species.
Received June 21, 2002; accepted October 4, 2002 Published online: Febraury 7, 2003 相似文献
7.
The rate of expansion of bacterial colonies of S. liquefaciens is investigated in terms of a mathematical model that combines biological as well as hydrodynamic processes. The relative
importance of cell differentiation and production of an extracellular wetting agent to bacterial swarming is explored using
a continuum representation. The model incorporates aspects of thin film flow with variable suspension viscosity, wetting,
and cell differentiation. Experimental evidence suggests that the bacterial colony is highly sensitive to its environment
and that a variety of mechanisms are exploited in order to proliferate on a variety of surfaces. It is found that a combination
of effects are required to reproduce the variation of bacterial colony motility over a large range of nutrient availability
and medium hardness.
Received: 29 April 1999 相似文献
8.
Cell division and cell differentiation are key processes in shoot development. The Arabidopsis thaliana (L.) Heynh. SCHIZOID (SHZ) gene appears to influence cell differentiation and cell division in the shoot. The shz-2 mutant is notable in that distinct phenotypes develop, depending on the environment in which the plants are grown. When shz-2 mutants are grown in petri dishes, callus develops from the petiole and hypocotyl. In contrast, when the mutants are grown
on soil, shoots appear externally stunted with malformed leaves. However, detailed examination of soil-grown mutants shows
that the two phenotypes are related. Soil-grown mutants form adventitious meristems, produce a large amount of vascular tissues
and have aberrant cell divisions in the meristem. Cells with abnormal cell-division patterns were found in the apical and
vascular meristems, suggesting SHZ influences cell division. Development of callus in petri dishes, development of adventitious meristems and aberrations in
leaves on soil suggest that SHZ influences cell differentiation. The distinct, but related phenotypes on soil and in petri dishes suggests that SHZ normally functions to regulate differentiation and/or cell division in a manner that is responsive to environmental conditions.
Received: 30 July 1999 / Accepted: 22 September 1999 相似文献
9.
Phytochrome-dependent growth in Dryopteris paleacea Sw. was investigated in young, developing gametophytes with respect to formation and differentiation of rhizoids. Under continuous
red light (Rc), the first rhizoids grew synchronously by tip elongation at a constant rate of 240 μm · d−1 until formation and outgrowth of the second rhizoid. Cessation of growth of the first rhizoids and outgrowth of the second
rhizoids showed a correlation in time assumed to be mediated by intercellular signaling. The first rhizoids showed two modes
of response to actinic irradiations: (i) modulation of rhizoid growth, and (ii) re-induction of growth in non-growing rhizoids.
In the former, the promotory effect of actinic irradiations on rhizoids pre-cultured under Rc determined both the time for
which rhizoids continued to grow after transfer into darkness and the final rhizoid length. In the latter, re-induced growth
was studied using non-growing rhizoids which were obtained after irradiation with a far-red light (FR) pulse at the end of
the pre-culture in Rc and transfer into darkness for 3 d to stop growth. Re-induction of growth occurred with a lag phase
of 36 to 48 h after formation of the FR-absorbing form of phytochrome (Pfr) by a red light (R) pulse. From the incomplete
R/FR reversibility it is evident that, here, coupling of Pfr to signal transduction is possible within minutes. Re-induction
of growth possesses the advantage that the effect of actinic irradiations can be studied as an all-or-none response at the
level of single gametophytes in future experiments. The present results clearly indicate that the developmental stage of the
whole gametophyte, i.e. temporal and spatial patterns undergone during development, affects the regulation of rhizoid growth
by the external factor light.
Received: 8 June 1998 / Accepted: 22 December 1998 相似文献
10.
During Arabidopsis embryogenesis, procambial cells undergo coordinated, asymmetric cell divisions, giving rise to vascular precursor cells (protophloem and protoxylem precursors). After germination, these cells terminally differentiate into specialized conducting cells, referred to as protophloem and protoxylem cells. Few readily identifiable markers of the onset of specification and differentiation are available, hampering the molecular genetic analysis of protophloem development. Confocal microscopy was used to investigate the patterning and differentiation of phloem cells during early plant development. Longitudinal divisions of phloem initials allowed the identification of protophloem precursor cells and adjacent metaphloem initials along the length of the plant. During germination, protophloem differentiation was observed at two independent locations, in the cotyledons and the hypocotyl. In both locations, differentiation was concomitant with cell elongation. We identified five gene-trap lines (PD1-PD5) with marker gene expression in immature protophloem elements. The spatio-temporal marker expression pattern of the lines divides them into two groups. The early specification markers PD4 and PD5 were expressed in developing organs before procambium formation and then became restricted to phloem initial cells. The protophloem precursor markers PD1-PD3 were expressed in differentiating protophloem cells at different stages of their development. All markers were expressed transiently and iteratively during the differentiation of protophloem in newly formed organs. Flanking genes were identified for four out of five gene-trap insertion lines. The possible function of these genes with respect to phloem differentiation is discussed. 相似文献
11.
The plant cytoskeleton has been implicated in a variety of morphogenetic events in higher plants. Most of this work, however,
has concentrated on epidermal cells or primary tissues. We have investigated the cortical microtubular (CMT) and microfilament
(MF) components of the cytoskeleton in a secondary tissue – active vascular cambium of Aesculus hippocastanum L. (horse-chestnut) – and followed the changes in these components during the early stages of differentiation of fusiform
cambial derivatives to axial elements of the secondary vascular system. A correlative approach was used employing indirect
immunofluorescence microscopy of α-tubulin on 6 μm sections, and transmission electron microscopy of 60 nm sections. The study
has demonstrated a rearrangement of the CMT cytoskeleton, from random to helical, as fusiform vascular cambial cells begin
to differentiate as secondary phloem vascular tissue. A similar CMT rearrangement is seen as fusiform cambial cells begin
to differentiate as secondary xylem fibres. This rearrangement is interpreted as evidence of determination of cambial derivatives
towards vascular development. Axially-oriented MF bundles are present in fusiform cambial cells and their axial orientation
is retained in the vascular derivatives at early stages of their development even though the CMTs have become rearranged.
Received: 5 August 1996 / Accepted: 23 September 1996 相似文献
12.
B. J. M. Zonneveld 《Plant Systematics and Evolution》2001,229(1-2):125-130
Genome size (C-values) and pollen viability staining were applied as new criteria to investigate the species of the genus
Helleborus Linnaeus (Ranunculaceae). All species have the same chromosome number (2n=32). However, the nuclear DNA content, as measured
by flow cytometry with propidium iodide, could be demonstrated to range between 19 pg to 35.7 pg. The different genome sizes
of the species coincided to a large extent with earlier determined section boundaries based on morphology. Flow cytometry
can be a convenient method to discriminate between some species.
Received April 17, 2001 Accepted May 7, 2001 相似文献
13.
The spatial pattern of acropetal and basipetal cytoplasmic streaming velocities has been studied by laser-Doppler-velocimetry
(LDV) in the positively gravitropic (downward growing) rhizoids of Chara globularis Thuill. and for the first time in the negatively gravitropic (upward growing) protonemata. The LDV method proved to be precise
and yielded reproducible results even when tiny differences in velocities were measured. In the apical parts of the streaming
regions of both cell types, acropetal streaming was faster than basipetal streaming. Starting at the apical reversal point
of streaming, the velocity increased basipetally with the distance from that point and became fairly constant close to the
basal reversal point; subsequently, the velocity decreased slightly acropetally as the apical reversal point was again approached.
There was no change in velocity at the basal reversal point. However, at the apical reversal point there was an abrupt decrease
in velocity. The pattern of the ratio of acropetal to basipetal streaming velocity (VR) was a function of the relative distance
of the site of measurement from the apical reversal point rather than a function of the absolute distance. Upon inversion
of the rhizoids, the VR decreased on average by 3.8% (±0.4%), indicating that the effect of gravity on the streaming velocity
was merely physical and without a physiological amplification. Rhizoids that had developed on the slowly rotating horizontal
axis of a clinostat, and had never experienced a constant gravity vector, were similar to normally grown rhizoids with respect
to VR pattern. In protonemata, the VR pattern was not significantly different from that in rhizoids although the direction
of growth was inverse. In rhizoids, oryzalin caused the polar organization of the cell to disappear and nullified the differences
in streaming velocities, and cytochalasin D decreased the velocity of basipetal streaming slightly more than that of acropetal
streaming. Cyclopiazonic acid, known as an inhibitor of the Ca2+-ATPase of the endoplasmic reticulum, also reduced the streaming velocities in rhizoids, but had slightly more effect on the
acropetal stream. It is possible that the endogenous difference in streaming velocities in both rhizoids and protonemata is
caused by differences in the cytoskeletal organization of the opposing streams and/or loading of inhibitors (like Ca2+) from the apical/subapical zone into the basipetally streaming endoplasm.
Received: 4 October 1999 / Accepted: 4 November 1999 相似文献
14.
Reversible protein phosphorylation regulates the dynamic organization of the pollen tube cytoskeleton: effects of calyculin A and okadaic acid 总被引:7,自引:0,他引:7
We investigated the cytoskeleton of Lilium longiflorum pollen tubes and examined the effects of the type 2A protein phosphatase (PP2A) inhibitors calyculin A and okadaic acid. An improved method for actin visualization, the simultaneous fixation and staining with rhodamine-labelled phalloidin during microscopical observation, revealed abundant actin filaments of no preferential orientation in the apical clear zone. Microtubules, visualized by indirect immunofluorescence, were mostly absent from the apices of straight-growing pollen tubes but present in those with irregular shape. Double labelling showed that both actin bundles and microtubules had a similar longitudinal or slightly helical orientation in the pollen tube shaft. In the presence of 30 nM calyculin A or okadaic acid, pollen tubes grew very slowly, branched frequently, and contained isolated, randomly oriented, curved actin bundles and microtubules. Treating pollen tubes with calyculin A or okadaic acid after germination arrested growth immediately, reversibly altered the alignment of actin bundles from axial to transverse, and disassembled microtubules. The changes in actin organization caused by the PP2A inhibitors were similar to those observed upon overexpression of AtRop1 (Y. Fu, G. Wu, Z. Yang, Journal of Cell Biology 152: 1019-1032, 2001), suggesting that hyperphosphorylation interferes with the signalling pathway of small GTPases. The effects of the PP2A inhibitors could be ameliorated with nanomolar concentrations of latrunculin B. 相似文献
15.
Bidens cordylocarpa is a high polyploid species restricted in distribution to stream sides in the mountains of Jalisco, Mexico. The morphologically
enigmatic species was originally described as a member of the genus Coreopsis, but later transferred to Bidens, largely because the involucral bracts appear most similar to Bidens. Characters of the cypselae, often useful in generic placement, are of no value for this species because the fruits have
features not detected in either Bidens or Coreopsis. Sequences from the internal transcribed spacer region of nuclear ribosomal DNA (ITS) were used to assess the relationships
of Bidens cordylocarpa. The molecular phylogeny places B. cordylocarpa in a strongly supported clade of Mexican and South American Bidens, and provides more definitive evidence of relationships than morphology, chromosome number, or secondary chemistry. Molecular,
morphological, and chromosomal data suggest that B. cordylocarpa is an ancient polyploid, perhaps the remnant of a polyploid complex.
Received August 28, 2000 Accepted February 11, 2001 相似文献
16.
The Involvement of Sphingolipids in Multidrug Resistance 总被引:13,自引:0,他引:13
Administration of most chemotherapeutic agents eventually results in the onset of apoptosis, despite the agents' variety
in structure and molecular targets. Ceramide, the central molecule in cellular glycosphingolipid metabolism, has recently
been identified as an important mediator of this process. Indeed, one of the events elicited by application of many cytotoxic
drugs is an accumulation of this lipid. Treatment failure in cancer chemotherapy is largely attributable to multidrug resistance,
in which tumor cells are typically cross-resistant to multiple chemotherapeutic agents. Different cellular mechanisms underlying
this phenomenon have been described. Of these the drug efflux pump activity of P-glycoprotein and the multidrug resistance-associated
proteins are the most extensively studied examples. Recently, an increased cellular capacity for ceramide glycosylation has
been recognized as a novel multidrug resistance mechanism. Indeed, virtually all multidrug-resistant cells exhibit a deviating
sphingolipid composition, most typically, increased levels of glucosylceramide. On the other hand, several direct molecular
interactions between sphingolipids and drug efflux proteins have been described. Therefore, in addition to a role in the multidrug
resistance phenotype by which ceramide accumulation and, thus, the onset of apoptosis are prevented, an indirect role for
sphingolipids might be envisaged, by which the activity of these efflux proteins is modulated. In this review, we present
an overview of the current understanding of the interesting relations that exist between sphingolipid metabolism and multidrug
resistance.
Received: 16 June 2000/Revised: 16 August 2000 相似文献
17.
R. Pozner 《Plant Systematics and Evolution》2001,230(1-2):25-42
Applying current data on cell differentia- tion and meiosis control to the early sporangial development in angiosperms, a
strict relationship between cell lineage and its differentiation fate is rejected. An evaluation of cytological features indicative
of a meiotic (sporogenous) fate discards the sterilization phenomenon and introduces the premeiotic cellular differentiation
(PCD) concept. The early sporangial development comprises 5 basic steps and 4 cellular stages, where PCD and meiosis extension
and gradient are related to mechanisms of spore mother cell selection. Concepts here discussed explain the exceptions to the
normal early sporangial development and allow a precise definition of archesporium and archespore. PCD and meiotic extension
and gradient recover more information of the early sporangial development, distinguishing different developmental patterns
leading to the same final result and retaining slight developmental differences. However, there are no early developmental
characteristics distinctive of andro- or gynosporangia. Therefore, the heterosporic condition is not related to early developmental
changes.
Received January 5, 2001 Accepted August 29, 2001 相似文献
18.
Excessive expression of the plant kinesin TBK5 converts cortical and perinuclear microtubules into a radial array emanating from a single focus 总被引:1,自引:0,他引:1
TBK5 is a plant-specific kinesin constantly expressed in tobacco BY-2 cells. An analysis of the distribution of green fluorescent protein-tagged TBK5 (GFP-TBK5) transiently expressed in BY-2 protoplasts revealed that TBK5 could associate with microtubules in vivo. GFP-TBK5 often assembled to form a single particle when accumulated in cells. The particle was located in close proximity to the nucleus, and its formation was accompanied by the development of a radial array of microtubules emanating from it and the loss of cortical microtubules. Microtubule depolymerization by treatment with propyzamide inhibited particle formation and stimulated the formation of dispersed aggregates of GFP-TBK5. Through expression of different TBK5 mutants as GFP fusions, the motor domain, two separated coiled-coil domains and the C-terminal domain of TBK5 were identified as the domains playing essential roles in particle formation. Mutants with putatively non-motile motor domains or lacking the C-terminal domain were localized to cortical and perinuclear microtubules, whereas those lacking either of the coiled-coil domains were preferentially distributed around the nucleus and along perinuclar microtubules. Further, the deletion of one of the coiled-coil domains or the C-terminal domain was sufficient to inhibit the propyzamide-induced formation of dispersed aggregates, whereas the mutation in the motor domain was not. These results led us to propose a model in which the particle is formed through the microtubule-based movement of GFP-TBK5 toward the nucleus and subsequent microtubule-independent aggregation based on coiled-coil interactions. The dramatic microtubule rearrangement would be explained if GFP-TBK5 relocated and gathered newly formed microtubules and/or microtubule-nucleating units. 相似文献
19.
Fifty natural Datura populations, belonging to eleven species (D. ceratocaula, D. discolor, D. inoxia, D. kymatocarpa, D. lanosa, D. metel, D. pruinosa, D. quercifolia, D. reburra, D. stramonium, D. wrightii) from Mexico and adjacent USA, were investigated using starch gel electrophoresis. A total of 64 alleles were scored at 17
loci (DIA1, DIA2, GOT1, GOT2, G6PDH, IDH, MDH1, MDH2, MDH3, ME, PGD1, PGD2, PGM1, PGM2, PHI, SAD, SOD). The heterozygosity
among the species ranged from 0.166 (D. ceratocaula) to 0.276 (D. wrightii). Most genetic diversity was found within populations (average Hs=0.242), while values between populations are relatively low (average Dst=0.066, Gst=0.171). The analysis of the genetic distance
suggested new taxonomic relationships among the species. Rather than supporting the conventional infrageneric classification
with three sections, the results revealed that the herbaceous members of the genus Datura form four groups. One group included four of the eight species of the section Dutra and was more similar to the section Ceratocaulis than it was to the other group that contained the remaining taxa of Dutra.
Received February 13, 2001 Accepted December 25, 2001 相似文献
20.
Small segments of Phycomyces sporangiophores regenerate various structures on incubation in a moist chamber. We tested the regeneration capacities of
middle sporangiophore segments whose protoplasm had been totally or partially removed and replaced with protoplasm from various
segments of a genetically different strain. The structures that were regenerated depended on the source of the injected protoplasm
(sporangia of various sizes and segments from middle and basal parts of the sporangiophores), implying a positional differentiation
of protoplasm along the sporangiophore axis. Protoplasm from various sources showed a high affinity; that is, they mixed successfully
and led, in most cases, to the formation of heterokaryotic regenerating structures. The highest affinity was seen when mixing
protoplasm from the middle segments of two different strains.
Received: November 29, 2000 / Accepted: March 19, 2002 相似文献