The auxin-insensitive bodenlos mutation affects primary root formation and apical-basal patterning in the Arabidopsis embryo

Development ◽  
1999 ◽  
Vol 126 (7) ◽  
pp. 1387-1395 ◽  
Author(s):  
T. Hamann ◽  
U. Mayer ◽  
G. Jurgens
Keyword(s):  
Daughter Cell ◽  
Root Formation ◽  
Normal Development ◽  
Root Meristem ◽  
Primary Root ◽  
Cell Stage ◽  
New Gene ◽  
Auxin Resistant1 ◽  
Auxin Analogue ◽  
Adult Plants

In Arabidopsis embryogenesis, the primary root meristem originates from descendants of both the apical and the basal daughter cell of the zygote. We have isolated a mutant of a new gene named BODENLOS (BDL) in which the primary root meristem is not formed whereas post-embryonic roots develop and bdl seedlings give rise to fertile adult plants. Some bdl seedlings lacked not only the root but also the hypocotyl, thus resembling monopteros (mp) seedlings. In addition, bdl seedlings were insensitive to the auxin analogue 2,4-D, as determined by comparison with auxin resistant1 (axr1) seedlings. bdl embryos deviated from normal development as early as the two-cell stage at which the apical daughter cell of the zygote had divided horizontally instead of vertically. Subsequently, the uppermost derivative of the basal daughter cell, which is normally destined to become the hypophysis, divided abnormally and failed to generate the quiescent centre of the root meristem and the central root cap. We also analysed double mutants. bdl mp embryos closely resembled the two single mutants, bdl and mp, at early stages, while bdl mp seedlings essentially consisted of hypocotyl but did form primary leaves. bdl axr1 embryos approached the mp phenotype at later stages, and bdl axr1 seedlings resembled mp seedlings. Our results suggest that BDL is involved in auxin-mediated processes of apical-basal patterning in the Arabidopsis embryo.

The role of the monopteros gene in organising the basal body region of the Arabidopsis embryo

Development ◽  
1993 ◽  
Vol 118 (2) ◽  
pp. 575-587 ◽  
Author(s):  
T. Berleth ◽  
G. Jurgens
Keyword(s):  
Tissue Culture ◽  
Pattern Formation ◽  
Basal Body ◽  
Root Formation ◽  
Root Meristem ◽  
Body Region ◽  
Phenotypic Trait ◽  
Embryo Cells ◽  
Stage Embryo

The monopteros (mp) gene contributes to apical-basal pattern formation in the Arabidopsis embryo. mp mutant seedlings lack basal body structures such as hypocotyl, radicle and root meristem, and this pattern deletion has been traced back to alterations in the octant-stage embryo. Cells of the embryo proper and the uppermost cell of the suspensor fail to establish division patterns that would normally generate the basal body structures. The resulting absence of a morphological axis seems to be responsible for another phenotypic trait of mp seedlings, variable positioning of cotyledons. This relationship is suggested by weak mp seedling phenotypes in which the presence of a short hypocotyl is correlated with normal arrangement of cotyledons. Root formation has been induced in mp seedlings grown in tissue culture. This result supports the notion that the mp gene is required for organising the basal body region, rather than for making the root, in the developing embryo.

Contribution of maternal factors and cellular interaction to determination of archenteron in the starfish embryo

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2619-2628 ◽  
Author(s):  
R. Kuraishi ◽  
L. Osanai
Keyword(s):  
Alkaline Phosphatase ◽  
Normal Development ◽  
Early Stage ◽  
Posterior Part ◽  
Immature Oocyte ◽  
Cellular Interaction ◽  
Cell Stage ◽  
Cytoplasmic Factor ◽  
Animal Pole

Contribution of maternal cytoplasmic factors and cellular interaction to determination of archenteron in a starfish embryo was analyzed by (1) examining temporal and positional pattern of expression of an endoderm-specific enzyme, alkaline phosphatase, (2) deleting the vegetal polar fragment from an immature oocyte and (3) changing the orientation of a blastomere within an early stage embryo. The archenteron (and the differentiated digestive tract) of Asterina pectinifera was divided into three areas based on the time of start of alkaline phosphatase expression. At 27 hours after 1-methyladenine treatment, the whole archenteron except the anterior end started to express alkaline phosphatase. The anterior negative area differentiated into mesodermal tissues such as mesenchyme cells and anterior coelomic pouches (anterior mesodermal area). The alkaline-phosphatase-positive area 1 gave rise to the esophagus and the anterior end of the stomach. Alkaline-phosphatase-positive area 2, which was gradually added to the posterior end of the archenteron after 30 hours, became alkaline-phosphatase- positive and formed the middle-to-posterior part of the stomach and the intestine. When the vegetal oocyte fragment, the volume of which was more than 8% of that of the whole oocyte, was removed from the immature oocyte, archenteron formation was strongly suppressed. However, when the volume deleted was less than 6%, most of the larvae started archenteron formation before the intact controls reached the mesenchyme-migration stage (30 hours). Although cells in the alkaline-phosphatase-positive area 2 are added to the posterior end of the archenteron after 30 hours in normal development (R. Kuraishi and K. Osanai (1992) Biol. Bull. Mar. Biol. Lab., Woods Hole 183, 258–268), few larvae started gastrulation after 30 hours. Estimation of the movement of the oocyte cortex during the early development suggested that the area that inherits the cortex of the 7% area coincides with the combined area of anterior mesodermal area and alkaline-phosphatase-positive area 1. When one of the blastomeres was rotated 180° around the axis of apicobasal polarity at the 2-cell stage to make its vegetal pole face the animal pole of the other blastomere, two archentera formed at the separated vegetal poles. Intracellular injection of tracers showed that cells derived from the animal blastomere, which gives rise to the ectoderm in normal development, stayed in the outer layer until 30 hours; a proportion of them then entered the archenteron gradually. The involuted animal cells expressed alkaline phosphatase and were incorporated into the middle-to-posterior part of the stomach and the intestine. These results suggest that anterior mesodermal area and alkaline-phosphatase-positive area 1 are determined by cytoplasmic factor(s) that had already been localized in their presumptive areas. In contrast, alkaline-phosphatase-positive area 2 becomes the endoderm by homoiogenetic induction from the neighboring area on the vegetal side, namely alkaline-phosphatase-positive area 1.

Fruiting body development in the mycetozoan Echinostelium bisporum

1989 ◽  
Vol 67 (5) ◽  
pp. 1285-1293 ◽  
Author(s):  
Frederick W. Spiegel ◽  
Joyce Feldman
Keyword(s):  
Daughter Cell ◽  
Spore Wall ◽  
Microtubule Organizing Center ◽  
Free Living ◽  
Cell Stage ◽  
Synaptonemal Complexes ◽  
Body Development ◽  
Prespore Cell ◽  
Fruiting Body Development ◽  
Organizing Center

Fruiting was followed from the prespore cell stage through the appearance of synaptonemal complexes in the spores in the simple mycetozoan Echinostelium bisporum. The prespore cell differentiates from a uninucleate amoeboflagellate that rounds up on the surface of the substrate. Centrioles are present in the prespore cell. As the prespore cell continues to differentiate it secretes a sheath and becomes nearly spherical. The prespore cell begins to lay down the stalk within an invagination, then rises as a sporogen at the tip of the stalk. By the sporogen stage the centrioles disappear and a spherical microtubule organizing center (MTOC) appears between the nucleus and the stalk apex. At the end of stalk elongation, the nucleus undergoes an apparently closed acentric mitosis and the sporogen cleaves into two hemispheres. Each daughter cell then rounds up and begins to produce a sculptured spore wall. The nuclei of the spores enter presumed meiotic prophase with synaptonemal complexes after the spore wall is complete. The spherical MTOC is present in all stages after the sporogen. These characters suggest that E. bisporum is a reduced myxomycete that has lost the free living plasmoidal stage of the life cycle.

Chromatin remodelling and nuclear reprogramming at the onset of embryonic development in mammals

1998 ◽  
Vol 10 (8) ◽  
pp. 573 ◽  
Author(s):  
Jean-Paul Renard
Keyword(s):  
Normal Development ◽  
Blastocyst Stage ◽  
Chromatin Remodelling ◽  
Chromatin Organization ◽  
Nuclear Reprogramming ◽  
Cell Stage ◽  
Donor Nucleus ◽  
The One ◽  
Kinetics Of ◽  
Determining Factor

Two main strategies are used to produce cloned mammals. The first involves the condensation of donor chromatin into chromosomes directly exposed to the recipient cytoplasm, whereas the second leaves the donor nucleus in interphase until the time of the first mitosis. Both strategies, which induce marked changes in chromatin organization, allow full reprogrammation of somatic-differentiated fetal and adult cells. This paper reviews some of the recent data that contribute to our understanding of chromatin remodelling at the onset of normal development, as well as after the introduction of a foreign nucleus into a recipient enucleated oocyte. These data indicate that the coordinated changes in chromatin organization that take place up until the first cellular differentiations at the blastocyst stage are determinants for successful cloning. Although some degree of synchronization between the cell cycle stages of donor and recipient cells is necessary for correct remodelling of a transferred nucleus, the kinetics of remodelling events occurring during the one-cell stage appears to be the determining factor for the normal onset of gene expression.

Morphological and Histochemical Studies of Primary Root Meristem of Rauwolfia vomitoria

1965 ◽  
Vol 126 (3) ◽  
pp. 204-208 ◽  
Author(s):  
Abdul J. Mia ◽  
Suman M. Pathak
Keyword(s):  
Root Meristem ◽  
Primary Root ◽  
Rauwolfia Vomitoria

An FGF signal from endoderm and localized factors in the posterior-vegetal egg cytoplasm pattern the mesodermal tissues in the ascidian embryo

Development ◽  
2000 ◽  
Vol 127 (13) ◽  
pp. 2853-2862 ◽  
Author(s):  
G.J. Kim ◽  
A. Yamada ◽  
H. Nishida
Keyword(s):  
Marginal Zone ◽  
Normal Development ◽  
Cell Stage ◽  
Asymmetric Divisions ◽  
Notochord Cells ◽  
Ascidian Embryos ◽  
The Difference ◽  
Mesenchyme Cells ◽  
Time Required ◽  
Ascidian Embryo

The major mesodermal tissues of ascidian larvae are muscle, notochord and mesenchyme. They are derived from the marginal zone surrounding the endoderm area in the vegetal hemisphere. Muscle fate is specified by localized ooplasmic determinants, whereas specification of notochord and mesenchyme requires inducing signals from endoderm at the 32-cell stage. In the present study, we demonstrated that all endoderm precursors were able to induce formation of notochord and mesenchyme cells in presumptive notochord and mesenchyme blastomeres, respectively, indicating that the type of tissue induced depends on differences in the responsiveness of the signal-receiving blastomeres. Basic fibroblast growth factor (bFGF), but not activin A, induced formation of mesenchyme cells as well as notochord cells. Treatment of mesenchyme-muscle precursors isolated from early 32-cell embryos with bFGF promoted mesenchyme fate and suppressed muscle fate, which is a default fate assigned by the posterior-vegetal cytoplasm (PVC) of the eggs. The sensitivity of the mesenchyme precursors to bFGF reached a maximum at the 32-cell stage, and the time required for effective induction of mesenchyme cells was only 10 minutes, features similar to those of notochord induction. These results support the idea that the distinct tissue types, notochord and mesenchyme, are induced by the same signaling molecule originating from endoderm precursors. We also demonstrated that the PVC causes the difference in the responsiveness of notochord and mesenchyme precursor blastomeres. Removal of the PVC resulted in loss of mesenchyme and in ectopic notochord formation. In contrast, transplantation of the PVC led to ectopic formation of mesenchyme cells and loss of notochord. Thus, in normal development, notochord is induced by an FGF-like signal in the anterior margin of the vegetal hemisphere, where PVC is absent, and mesenchyme is induced by an FGF-like signal in the posterior margin, where PVC is present. The whole picture of mesodermal patterning in ascidian embryos is now known. We also discuss the importance of FGF induced asymmetric divisions, of notochord and mesenchyme precursor blastomeres at the 64-cell stage.

Interactions of different vegetal cells with mesomeres during early stages of sea urchin development

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 881-890 ◽  
Author(s):  
O. Khaner ◽  
F. Wilt
Keyword(s):  
Sea Urchin ◽  
Normal Development ◽  
Pigment Cells ◽  
Regional Differentiation ◽  
Cell Type ◽  
Animal Cells ◽  
Cell Stage ◽  
Latent Ability ◽  
A Cell ◽  
Poorly Differentiated

It has been known from results obtained in the classical experiments on sea urchin embryos that cell isolation and transplantation showed extensive interactions between the early blastomeres and/or their descendants. In the experiments reported here a systematic reexamination of recombination of mesomeres and their progeny (which come from the animal hemisphere) with various vegetal cells derived from blastomeres of the 32- and 64-cell stage was carried out. Cells were marked with lineage tracers to follow which cell gave rise to what structures, and newly available molecular markers have been used to analyze different structures characteristic of regional differentiation. Large micromeres form spicules and induce gut and pigment cells in mesomeres, conforming to previous results. Small micromeres, a cell type not heretofore examined, gave rise to no recognizable structure and had very limited ability to evoke poorly differentiated gut tissue in mesomeres. Macromeres and their descendants, Veg 1 and Veg 2, form primarily what their normal fate dictated, though both did have some capacity to form spicules, presumably by formation from secondary mesenchyme. Macromeres and their descendants were not potent inducers of vegetal structures in animal cells, but they suppress the latent ability of mesomeres to form vegetal structures. The results lead us to propose that the significant interactions during normal development may be principally suppressive effects of mesomeres on one another and of adjacent vegetal cells on mesomeres.

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