scholarly journals Embryonic Structure

2020 ◽  
Author(s):  
Keyword(s):  
Embryonic Structure

scholarly journals Brassinosteroids repress the seed maturation program during the seed-to-seedling transition

2021 ◽  
Author(s):  
Jiuxiao Ruan ◽  
Huhui Chen ◽  
Tao Zhu ◽  
Yaoguang Yu ◽  
Yawen Lei ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Transcription Factor ◽  
Abscisic Acid ◽  
Plant Hormone ◽  
Flowering Plants ◽  
Seed Maturation ◽  
Domain Protein ◽  
Abscisic Acid Insensitive3 ◽  
Underlying Mechanisms ◽  
Embryonic Structure

Abstract In flowering plants, repression of the seed maturation program is essential for the transition from the seed to the vegetative phase, but the underlying mechanisms remain poorly understood. The B3-domain protein VIVIPAROUS1/ABSCISIC ACID-INSENSITIVE3-LIKE 1 (VAL1) is involved in repressing the seed maturation program. Here we uncovered a molecular network triggered by the plant hormone brassinosteroid (BR) that inhibits the seed maturation program during the seed-to-seedling transition in Arabidopsis (Arabidopsis thaliana). val1-2 mutant seedlings treated with a BR biosynthesis inhibitor form embryonic structures, whereas BR signaling gain-of-function mutations rescue the embryonic structure trait. Furthermore, the BR-activated transcription factors BRI1-EMS-SUPPRESSOR 1 and BRASSINAZOLE-RESISTANT 1 bind directly to the promoter of AGAMOUS-LIKE15 (AGL15), which encodes a transcription factor involved in activating the seed maturation program, and suppress its expression. Genetic analysis indicated that BR signaling is epistatic to AGL15 and represses the seed maturation program by downregulating AGL15. Finally, we showed that the BR-mediated pathway functions synergistically with the VAL1/2-mediated pathway to ensure the full repression of the seed maturation program. Together, our work uncovered a mechanism underlying the suppression of the seed maturation program, shedding light on how BR promotes seedling growth.

Regionalization within the mammalian telencephalon is mediated by changes in responsiveness to Sonic Hedgehog

Development ◽  
1998 ◽  
Vol 125 (24) ◽  
pp. 5079-5089 ◽  
Author(s):  
J.D. Kohtz ◽  
D.P. Baker ◽  
G. Corte ◽  
G. Fishell
Keyword(s):  
Basal Ganglia ◽  
Globus Pallidus ◽  
Sonic Hedgehog ◽  
Adult Brain ◽  
Ganglionic Eminence ◽  
Lateral Ganglionic Eminence ◽  
Expression Characteristic ◽  
Sonic Hedgehog Gene ◽  
Embryonic Structure ◽  
Sequential Induction

The cortex and basal ganglia are the major structures of the adult brain derived from the embryonic telencephalon. Two morphologically distinct regions of the basal ganglia are evident within the mature ventral telencephalon, the globus pallidus medially, and the striatum, which is positioned between the globus pallidus and the cortex. Deletion of the Sonic Hedgehog gene in mice indicates that this secreted signaling molecule is vital for the generation of both these ventral telencephalic regions. Previous experiments showed that Sonic Hedgehog induces differentiation of ventral neurons characteristic of the medial ganglionic eminence, the embryonic structure which gives rise to the globus pallidus. In this paper, we show that later in development, Sonic Hedgehog induces ventral neurons with patterns of gene expression characteristic of the lateral ganglionic eminence. This is the embryonic structure from which the striatum is derived. These results suggest that temporally regulated changes in Sonic Hedgehog responsiveness are integral in the sequential induction of basal telencephalic structures.

scholarly journals XV. On the chorda dorsalis

1841 ◽  
Vol 131 ◽  
pp. 195-199
Keyword(s):  
Whole Body ◽  
Chorda Dorsalis ◽  
Embryonic Structure

For the discovery of the remarkable structure in the embryo of some of the Vertebrata denominated the chorda dorsalis, we are indebted to Professor Baer. This naturalist considered it “the axis around which the first parts of the fœtus form,” and “the true virga mensoria for the whole body and all the chief systems.” Reichert supposes it to be that embryonic structure which serves as a “support and stay” for parts developed in two halves. In the course of my researches on the mammiferous ovum, an object was noticed which seems to correspond in appearance to the incipient chorda now referred to. I am desirous of drawing attention to this similarity in appearance, but more particularly to point out some important differences between my own observations and those of others, as to the mode of origin of the objects in question, and their relation to surrounding parts. For, should it be found that these objects are the same, my belief is that even the most recent views on the incipient growth of the embryo must undergo a change.

Neurobiology of Monotremes

2013 ◽  
Keyword(s):  
Structure Function ◽  
Universal System ◽  
Detailed Review ◽  
Sensory Pathways ◽  
Key Points ◽  
Physiological Adaptations ◽  
The One ◽  
Development Structure ◽  
Embryonic Structure ◽  
Brain Atlases

Neurobiology of Monotremes brings together current information on the development, structure, function and behavioural ecology of the monotremes. The monotremes are an unusual and evolutionarily important group of mammals showing striking behavioural and physiological adaptations to their niches. They are the only mammals exhibiting electroreception (in the trigeminal sensory pathways) and the echidna shows distinctive olfactory specialisations. The authors aim to close the current gap in knowledge between the genes and developmental biology of monotremes on the one hand, and the adult structure, function and ecology of monotremes on the other. They explore how the sequence 'embryonic structure › adult structure › behaviour' is achieved in monotremes and how this differs from other mammals. The work also combines a detailed review of the neurobiology of monotremes with photographic and diagrammatic atlases of the sectioned adult brains and peripheral nervous system of the short-beaked echidna and platypus. Pairing of a detailed review of the field with the first published brain atlases of two of the three living monotremes will allow the reader to immediately relate key points in the text to features in the atlases and will extend a universal system of brain nomenclature developed in eutherian brain atlases by G Paxinos and colleagues to monotremes.

scholarly journals Development of Embryo Suspensors for Five Genera of Crassulaceae with Special Emphasis on Plasmodesmata Distribution and Ultrastructure

Plants ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 320 ◽  
Author(s):  
Małgorzata Kozieradzka-Kiszkurno ◽  
Daria Majcher ◽  
Emilia Brzezicka ◽  
Joanna Rojek ◽  
Justyna Wróbel-Marek ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Basal Cell ◽  
Lipid Droplets ◽  
Cell Structure ◽  
Cell Transfer ◽  
Electron Dense Material ◽  
Full Development ◽  
The One ◽  
Embryonic Structure ◽  
Suspensor Cells

The suspensor in the majority of angiosperms is an evolutionally conserved embryonic structure functioning as a conduit that connects ovule tissues with the embryo proper for nutrients and growth factors flux. This is the first study serving the purpose of investigating the correlation between suspensor types and plasmodesmata (PD), by the ultrastructure of this organ in respect of its full development. The special attention is paid to PD in representatives of Crassulaceae genera: Sedum, Aeonium, Monanthes, Aichryson and Echeveria. The contribution of the suspensor in transporting nutrients to the embryo was confirmed by the basal cell structure of the suspensor which produced, on the micropylar side of all genera investigated, a branched haustorium protruding into the surrounding ovular tissue and with wall ingrowths typically associated with cell transfer. The cytoplasm of the basal cell was rich in endoplasmic reticulum, mitochondria, dictyosomes, specialized plastids, microtubules, microbodies and lipid droplets. The basal cell sustained a symplasmic connection with endosperm and neighboring suspensor cells. Our results indicated the dependence of PD ultrastructure on the type of suspensor development: (i) simple PD are assigned to an uniseriate filamentous suspensor and (ii) PD with an electron-dense material are formed in a multiseriate suspensor. The occurrence of only one or both types of PD seems to be specific for the species but not for the genus. Indeed, in the two tested species of Sedum (with the distinct uniseriate/multiseriate suspensors), a diversity in the structure of PD depends on the developmental pattern of the suspensor. In all other genera (with the multiseriate type of development of the suspensor), the one type of electron-dense PD was observed.

scholarly journals Persistent Embryonic Structure

2020 ◽  
Author(s):  
Keyword(s):  
Embryonic Structure

Hypochord, an enigmatic embryonic structure: Study of the axolotl embryo

1997 ◽  
Vol 232 (1) ◽  
pp. 57-66 ◽  
Author(s):  
Jan Löfberg ◽  
Andres Collazo
Keyword(s):  
Structure Study ◽  
Embryonic Structure

scholarly journals Embryology of the lamprey and evolution of the vertebrate jaw: insights from molecular and developmental perspectives

2001 ◽  
Vol 356 (1414) ◽  
pp. 1615-1632 ◽  
Author(s):  
Shigeru Kuratani ◽  
Yoshiaki Nobusada ◽  
Naoto Horigome ◽  
Yasuyo Shigetani
Keyword(s):  
Gene Expression ◽  
Nasal Septum ◽  
Expression Patterns ◽  
Regulatory Gene ◽  
Evolutionary Developmental Biology ◽  
Gene Expression Patterns ◽  
Upper Lip ◽  
Jaw Apparatus ◽  
Equivalent Site ◽  
Embryonic Structure

Evolution of the vertebrate jaw has been reviewed and discussed based on the developmental pattern of the Japanese marine lamprey, Lampetra japonica . Though it never forms a jointed jaw apparatus, the L. japonica embryo exhibits the typical embryonic structure as well as the conserved regulatory gene expression patterns of vertebrates. The lamprey therefore shares the phylotype of vertebrates, the conserved embryonic pattern that appears at pharyngula stage, rather than representing an intermediate evolutionary state. Both gnathostomes and lampreys exhibit a tripartite configuration of the rostral–most crest–derived ectomesenchyme, each part occupying an anatomically equivalent site. Differentiated oral structure becomes apparent in post–pharyngula development. Due to the solid nasohypophyseal plate, the post–optic ectomesenchyme of the lamprey fails to grow rostromedially to form the medial nasal septum as in gnathostomes, but forms the upper lip instead. The gnathostome jaw may thus have arisen through a process of ontogenetic repatterning, in which a heterotopic shift of mesenchyme–epithelial relationships would have been involved. Further identification of shifts in tissue interaction and expression of regulatory genes are necessary to describe the evolution of the jaw fully from the standpoint of evolutionary developmental biology.

IN WHAT EMBRYONIC STAGE DO THE EGGS OF NEODIPRION ENTER THE WINTER DIAPAUSE?

1952 ◽  
Vol 30 (2) ◽  
pp. 99-108 ◽  
Author(s):  
Wolodymyr Brygider
Keyword(s):  
Embryonic Development ◽  
Early Embryonic Development ◽  
Embryonic Stage ◽  
Embryonic Structure

This paper deals with the early embryonic development of Neodiprion banksianae Roh., N. nanulus Schedl., and N. sertifer Geoff., up to the initiation of winter diapause. Methods of preparation are described and the course of development is traced and described with the aid of two text-figures and two plates. The three species were found to enter diapause at approximately the same stage, but some differences in the details of their embryonic structure were discovered.

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