The Role of Auxin in Apical-Basal Pattern Formation During Arabidopsis Embryogenesis

2001 ◽  
Vol 20 (3) ◽  
pp. 292-299 ◽  
Author(s):  
Thorsten Hamann
Keyword(s):  
Pattern Formation ◽  
Arabidopsis Embryogenesis

Role of Nuclei in Liesegang Pattern Formation: Insights from Experiment and Reaction-Diffusion Simulation

2018 ◽  
Vol 122 (6) ◽  
pp. 3669-3676 ◽  
Author(s):  
Masaki Itatani ◽  
Qing Fang ◽  
Kei Unoura ◽  
Hideki Nabika
Keyword(s):  
Pattern Formation ◽  
Reaction Diffusion ◽  
Diffusion Simulation

Citral, an inhibitor of retinoic acid synthesis, modifies pattern formation during limb regeneration in the axolotl Ambystoma mexicanum

1999 ◽  
Vol 77 (11) ◽  
pp. 1835-1837 ◽  
Author(s):  
Steven R Scadding
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Limb Regeneration ◽  
Acid Synthesis ◽  
Ambystoma Mexicanum

While the effects of exogenous retinoids on amphibian limb regeneration have been studied extensively, the role of endogenous retinoids is not clear. Hence, I wished to investigate the role of endogenous retinoic acid during axolotl limb regeneration. Citral is a known inhibitor of retinoic acid synthesis. Thus, I treated regenerating limbs of the larval axolotl Ambystoma mexicanum with citral. The result of this inhibition of retinoic acid synthesis was that limb regeneration became extremely irregular and hypomorphic, with serious pattern defects, or was inhibited altogether. I conclude that endogenous retinoic acid plays an important role in pattern formation during limb regeneration.

‘Generic’ physical mechanisms of morphogenesis and pattern formation

Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 1-18 ◽  
Author(s):  
S.A. Newman ◽  
W.D. Comper
Keyword(s):  
Pattern Formation ◽  
Reaction Diffusion ◽  
Physical Mechanisms ◽  
Extracellular Matrix Components ◽  
Genetic Mechanisms ◽  
Chemical Waves ◽  
Phylogenetic Lineages ◽  
Living Tissues ◽  
Highly Evolved

The role of ‘generic’ physical mechanisms in morphogenesis and pattern formation of tissues is considered. Generic mechanisms are defined as those physical processes that are broadly applicable to living and non-living systems, such as adhesion, surface tension and gravitational effects, viscosity, phase separation, convection and reaction-diffusion coupling. They are contrasted with ‘genetic’ mechanisms, a term reserved for highly evolved, machine-like, biomolecular processes. Generic mechanisms acting upon living tissues are capable of giving rise to morphogenetic rearrangements of cytoplasmic, tissue and extracellular matrix components, sometimes leading to ‘microfingers’, and to chemical waves or stripes. We suggest that many morphogenetic and patterning effects are the inevitable outcome of recognized physical properties of tissues, and that generic physical mechanisms that act on these properties are complementary to, and interdependent with genetic mechanisms. We also suggest that major morphological reorganizations in phylogenetic lineages may arise by the action of generic physical mechanisms on developing embryos. Subsequent evolution of genetic mechanisms could stabilize and refine developmental outcomes originally guided by generic effects.

Reorganization of membrane contacts prior to apoptosis in the Drosophila retina: the role of the IrreC-rst protein

Development ◽  
1996 ◽  
Vol 122 (6) ◽  
pp. 1931-1940 ◽  
Author(s):  
C. Reiter ◽  
T. Schimansky ◽  
Z. Nie ◽  
K.F. Fischbach
Keyword(s):  
Pattern Formation ◽  
Pigment Cells ◽  
Immunoglobulin Superfamily ◽  
Specific Cell ◽  
Axonal Pathfinding ◽  
Single Row ◽  
Cell Contacts ◽  
Regulated Expression ◽  
Membrane Contacts

The final step of pattern formation in the developing retina of Drosophila is the elimination of excess cells between ommatidia and the differentiation of the remaining cells into secondary and tertiary pigment cells. Temporally and spatially highly regulated expression of the irregular chiasmC-roughest protein, an adhesion molecule of the immunoglobulin superfamily known to be involved in axonal pathfinding, is essential for correct sorting of cell-cell contacts in the pupal retina without which the ensuing wave of apoptosis does not occur. Irregular chiasmC-roughest accumulates strongly at the borders between primary pigment and interommatidial cells. Mutant and misexpression analysis show that this accumulation of the irregular chiasmC-roughest protein is necessary for aligning interommatidial cells in a single row. This reorganisation is a prerequisite for the identification of death candidates. Irregular chiasmC-roughest function in retinal development demonstrates the importance of specific cell contacts for assignment of the apoptotic fate.

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.

Compartments, wingless and engrailed: patterning the ventral epidermis of Drosophila embryos

Development ◽  
1996 ◽  
Vol 122 (12) ◽  
pp. 4095-4103 ◽  
Author(s):  
P.A. Lawrence ◽  
B. Sanson ◽  
J.P. Vincent
Keyword(s):  
Pattern Formation ◽  
Wing Disc ◽  
High Concentration ◽  
Good Region ◽  
Steep Slopes ◽  
Cuticular Structures ◽  
Different Levels ◽  
Promote Cell Death ◽  
Drosophila Embryos

Recent experiments on the wing disc of Drosophila have shown that cells at the interface between the anterior and posterior compartments drive pattern formation by becoming the source of a morphogen. Here we ask whether this model applies to the ventral embryonic epidermis. First, we show that interfaces between posterior (engrailed ON) and anterior (engrailed OFF) cells are required for pattern formation. Second, we provide evidence that Wingless could play the role of the morphogen, at least within part of the segmental pattern. We looked at the cuticular structures that develop after different levels of uniform Wingless activity are added back to unsegmented embryos (wingless- engrailed-). Because it is rich in landmarks, the T1 segment is a good region to analyse. There, we find that the cuticle formed depends on the amount of added Wingless activity. For example, a high concentration of Wingless gives the cuticle elements normally found near the top of the presumed gradient. Unsegmented embryos are much shorter than wild type. If Wingless activity is added in stripes, the embryos are longer than if it is added uniformly. We suggest that the Wingless gradient landscape affects the size of the embryo, so that steep slopes would allow cells to survive and divide, while an even distribution of morphogen would promote cell death. Supporting the hypothesis that Wingless acts as a morphogen, we find that these stripes affect, at a distance, the type of cuticle formed and the planar polarity of the cells.

Apical-basal pattern formation in the Arabidopsis embryo: studies on the role of the gnom gene

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 149-162 ◽  
Author(s):  
U. Mayer ◽  
G. Buttner ◽  
G. Jurgens
Keyword(s):  
Pattern Formation ◽  
Root Formation ◽  
Asymmetric Cell Division ◽  
Early Embryo ◽  
The Body ◽  
Wild Type ◽  
Early Effect ◽  
Normal Number ◽  
Mutant Seedling

gnom is one of several genes that make substantial contributions to pattern formation along the apical-basal axis of polarity in the Arabidopsis embryo as indicated by the mutant seedling phenotype. The apical and basal end regions of the body pattern, which include the meristems of the shoot and the root, fail to form, and a minority of mutant embryos lack morphological features of apical-basal polarity. We have investigated the developmental basis of the gnom mutant phenotype, taking advantage of a large number of EMS-induced mutant alleles. The seedling phenotype has been traced back to the early embryo in which the asymmetric division of the zygote is altered, now producing two nearly equal-sized cells. The apical daughter cell then undergoes abnormal divisions, resulting in an octant embryo with about twice the normal number of cells while the uppermost derivative of the basal cell fails to become the hypophysis, which normally contributes to root development. Consistent with this early effect, gnom appears to be epistatic to monopteros in doubly mutant embryos, suggesting that, without prior gnom activity, the monopteros gene cannot promote root and hypocotyl development. On the other hand, when root formation was induced in bisected seedlings, wild-type responded whereas gnom mutants failed to produce a root but formed callus instead. These results suggest that gnom activity promotes asymmetric cell division which we believe is necessary both for apical-basal pattern formation in the early embryo and for root formation in tissue culture.

The segment polarity gene armadillo interacts with the wingless signaling pathway in both embryonic and adult pattern formation

Development ◽  
1991 ◽  
Vol 111 (4) ◽  
pp. 1029-1043 ◽  
Author(s):  
M. Peifer ◽  
C. Rauskolb ◽  
M. Williams ◽  
B. Riggleman ◽  
E. Wieschaus
Keyword(s):  
Pattern Formation ◽  
Imaginal Discs ◽  
Protein Accumulation ◽  
Segment Polarity Genes ◽  
Adult Pattern ◽  
Segment Polarity ◽  
Lethal Allele ◽  
Segment Polarity Gene ◽  
Polarity Gene

The segment polarity genes of Drosophila were initially defined as genes required for pattern formation within each embryonic segment. Some of these genes also function to establish the pattern of the adult cuticle. We have examined the role of the armadillo (arm) gene in this latter process. We confirmed and extended earlier findings that arm and the segment polarity gene wingless are very similar in their effects on embryonic development. We next discuss the role of arm in pattern formation in the imaginal discs, as determined by using a pupal lethal allele, by analyzing clones of arm mutant tissue in imaginal discs, and by using a transposon carrying arm to produce adults with a reduced level of arm. Together, these experiments established that arm is required for the development of all imaginal discs. The requirement for arm varies along the dorsal-ventral and proximal-distal axes. Cells that require the highest levels of arm are those that express the wingless gene. Further, animals with reduced arm levels have phenotypes that resemble those of weak alleles of wingless. We present a description of the patterns of arm protein accumulation in imaginal discs. Finally, we discuss the implications of these results for the role of arm and wingless in pattern formation.

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