scholarly journals Valois, a component of the nuage and pole plasm, is involved in assembly of these structures, and binds to Tudor and the methyltransferase Capsuleen

Development ◽  
2005 ◽  
Vol 132 (9) ◽  
pp. 2167-2177 ◽  
Author(s):  
J. Anne
Keyword(s):  
Pole Plasm

Development of the germ cells and reproductive primordia in male and female embryos of Rhodnius prolixus Stål (Hemiptera: Reduviidae)

1994 ◽  
Vol 72 (6) ◽  
pp. 1100-1119 ◽  
Author(s):  
B. S. Heming ◽  
E. Huebner
Keyword(s):  
Germ Cells ◽  
Dorsal Surface ◽  
Interstitial Cells ◽  
Rhodnius Prolixus ◽  
Posterior Pole ◽  
Male And Female ◽  
Functional Aspects ◽  
Pole Plasm ◽  
Blastodermal Cells ◽  
Sheath Cells

Newly deposited eggs of Rhodnius prolixus lack a visible pole plasm and require 14 days to develop at 27 °C and 70% RH. The first germ cells originate at 9% of embryogenesis by asynchronous mitosis of blastodermal cells behind the germ Anlage at the posterior pole of the egg. From 9 to 17%, these proliferate to a mean of 270 cells and, from 13 to 18%, migrate forward over the dorsal surface of the mesoderm and lodge in abdominal segments 3–7. Between 22 and 30%, they shift laterally and segregate into three or four paired clumps between segments 3 and 4, 4 and 5, 5 and 6, and, sometimes, 6 and 7 and, from 30 to 37%, gradually assemble into a continuous longitudinal mass on either side of segments 3–6, where they begin to associate with mesodermal cells. Between 37 and 46%, these collect between (males) and around the germ cells to form the rudiments of the terminal filaments (females), inner and outer gonadal sheaths, interstitial cells (males), and primary exit ducts. Dorsally situated sheath cells then invaginate ventrally into each gonadal rudiment, partitioning it into seven compartments, each containing a mean of 15 oogonia or 16 spermatogonia. These seem to fuse into a rosette, at least in females, but do not begin to divide again until after hatch. Excluded germ cells lodge within the rudiments of one or both exit ducts. The evolutionary and functional aspects of our findings are addressed and new observations are presented on the mechanism of anatrepsis.

scholarly journals Mitochondrial DNA segregation and replication restrict the transmission of detrimental mutation

2020 ◽  
Vol 219 (7) ◽  
Author(s):  
Zhe Chen ◽  
Zong-Heng Wang ◽  
Guofeng Zhang ◽  
Christopher K.E. Bleck ◽  
Dillon J. Chung ◽  
...  
Keyword(s):  
Mitochondrial Dna ◽  
Stress Test ◽  
Mitochondrial Fission ◽  
Minor Role ◽  
Deleterious Mutations ◽  
Mtdna Mutations ◽  
Electron Transport Chains ◽  
Repair Mechanisms ◽  
A Minor ◽  
Pole Plasm

Although mitochondrial DNA (mtDNA) is prone to accumulate mutations and lacks conventional DNA repair mechanisms, deleterious mutations are exceedingly rare. How the transmission of detrimental mtDNA mutations is restricted through the maternal lineage is debated. Here, we demonstrate that mitochondrial fission, together with the lack of mtDNA replication, segregate mtDNA into individual organelles in the Drosophila early germarium. After mtDNA segregation, mtDNA transcription begins, which activates respiration. Mitochondria harboring wild-type genomes have functional electron transport chains and propagate more vigorously than mitochondria containing deleterious mutations in hetreoplasmic cells. Therefore, mtDNA expression acts as a stress test for the integrity of mitochondrial genomes and sets the stage for replication competition. Our observations support selective inheritance at the organelle level through a series of developmentally orchestrated mitochondrial processes. We also show that the Balbiani body has a minor role in mtDNA selective inheritance by supplying healthy mitochondria to the pole plasm. These two mechanisms may act synergistically to secure the transmission of functional mtDNA through Drosophila oogenesis.

Restoration of the capacity to form pole cells in u.v.-irradiated Drosophila embryos

Development ◽  
1975 ◽  
Vol 33 (4) ◽  
pp. 1003-1011
Author(s):  
Richard Warn
Keyword(s):  
Pole Cell ◽  
Pole Cells ◽  
Pole Plasm ◽  
Cell Fragments ◽  
Drosophila Embryos

Injection of pole plasm into u.v.-irradiated posterior poles of early Drosophila embryos leads to the restoration of the capacity to form pole cells in nearly half of the recipients. The effect is specific, since cytoplasm from the anterior tip has no such result. In most cases only a small number (between 1 and 5) of discrete pole cells are formed. However, a large number of pole cell fragments with or without nuclei occur. Occasionally pole cells were formed outside the area of the originally irradiated pole plasm. This happened when material was injected more anteriorly than usual. Thus polar cytoplasm contains some factor(s) necessary for the formation of pole cells.

Oskar anchoring restricts pole plasm formation to the posterior of the Drosophila oocyte

Development ◽  
2002 ◽  
Vol 129 (15) ◽  
pp. 3705-3714 ◽  
Author(s):  
Nathalie F. Vanzo ◽  
Anne Ephrussi
Keyword(s):  
Drosophila Melanogaster ◽  
Translational Control ◽  
Cell Formation ◽  
Positional Information ◽  
Mrna Localization ◽  
Posterior Pole ◽  
Tight Coupling ◽  
Anteroposterior Patterning ◽  
Pole Cell ◽  
Pole Plasm

Localization of the maternal determinant Oskar at the posterior pole of Drosophila melanogaster oocyte provides the positional information for pole plasm formation. Spatial control of Oskar expression is achieved through the tight coupling of mRNA localization to translational control, such that only posterior-localized oskar mRNA is translated, producing the two Oskar isoforms Long Osk and Short Osk. We present evidence that this coupling is not sufficient to restrict Oskar to the posterior pole of the oocyte. We show that Long Osk anchors both oskar mRNA and Short Osk, the isoform active in pole plasm assembly, at the posterior pole. In the absence of anchoring by Long Osk, Short Osk disperses into the bulk cytoplasm during late oogenesis, impairing pole cell formation in the embryo. In addition, the pool of untethered Short Osk causes anteroposterior patterning defects, owing to the dispersion of pole plasm and its abdomen-inducing activity throughout the oocyte. We show that the N-terminal extension of Long Osk is necessary but not sufficient for posterior anchoring, arguing for multiple docking elements in Oskar. This study reveals cortical anchoring of the posterior determinant Oskar as a crucial step in pole plasm assembly and restriction, required for proper development of Drosophila melanogaster.

scholarly journals vasa is required for GURKEN accumulation in the oocyte, and is involved in oocyte differentiation and germline cyst development

Development ◽  
1998 ◽  
Vol 125 (9) ◽  
pp. 1569-1578 ◽  
Author(s):  
S. Styhler ◽  
A. Nakamura ◽  
A. Swan ◽  
B. Suter ◽  
P. Lasko
Keyword(s):  
Embryonic Patterning ◽  
Wild Type ◽  
Coding Region ◽  
Cell Specification ◽  
Germline Cyst ◽  
And Function ◽  
Oocyte Differentiation ◽  
Pole Plasm ◽  
Anterior Posterior

The Drosophila gene vasa is required for pole plasm assembly and function, and also for completion of oogenesis. To investigate the role of vasa in oocyte development, we generated a new null mutation of vasa, which deletes the entire coding region. Analysis of vasa-null ovaries revealed that the gene is involved in the growth of germline cysts. In vasa-null ovaries, germaria are atrophied, and contain far fewer developing cysts than do wild-type germaria; a phenotype similar to, but less severe than, that of a null nanos allele. The null mutant also revealed roles for vasa in oocyte differentiation, anterior-posterior egg chamber patterning, and dorsal-ventral follicle patterning, in addition to its better-characterized functions in posterior embryonic patterning and pole cell specification. The anterior-posterior and dorsal-ventral patterning phenotypes resemble those observed in gurken mutants. vasa-null oocytes fail to efficiently accumulate many localized RNAs, such as Bicaudal-D, orb, oskar, and nanos, but still accumulate gurken RNA. However, GRK accumulation in the oocyte is severely reduced in the absence of vasa function, suggesting a function for VASA in activating gurken translation in wild-type ovaries.

Experimental studies on the role of ‘polar granules’ in the segregation of pole cells in Drosophila melanogaster

Development ◽  
1966 ◽  
Vol 16 (3) ◽  
pp. 391-399
Author(s):  
Bożenna Jazdowska-Zagrodzińska
Keyword(s):  
Germ Cells ◽  
Normal Development ◽  
Primordial Germ Cells ◽  
Experimental Studies ◽  
Main Body ◽  
Track Formation ◽  
Polar Granules ◽  
Pole Cells ◽  
Pole Plasm

The early differentiation of germ cells is a common phenomenon in the animal kingdom. Insects are of special interest in this respect, as the differentiation of their primordial germ cells occurs in very early stages of cleavage (Kahle, 1908; Hegner, 1914; Reitberger, 1934; Kraczkiewicz, 1935, 1936) and the structure of the ooplasm enables relatively convenient observation of the phenomenon of germ track formation. The ooplasm is differentiated in that the posterior end of the egg contains the so-called ‘pole plasm’ in which there are easily visible inclusions quite different from yolk, though staining similarly with haematoxylin. Such inclusions are not noted in other parts of the egg. In the course of normal development the region containing granules and pole plasm always detaches, producing the primordial germ cells. During the separation of the primordial germ cells, also called pole cells, all these granules become included in their cytoplasm, and the main body of ooplasm is left devoid of them.

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