The distribution of cytoplasmic bacteria in the early Drosophila embryo is mediated by astral microtubules

1994 ◽  
Vol 107 (3) ◽  
pp. 673-682 ◽  
Author(s):  
G. Callaini ◽  
M.G. Riparbelli ◽  
R. Dallai
Keyword(s):  
Cortical Layer ◽  
Drosophila Embryo ◽  
Mitotic Spindles ◽  
Embryo Viability ◽  
Polar Bodies ◽  
Early Drosophila Embryo ◽  
Close Relationship ◽  
Different Strains ◽  
Partial Dissociation ◽  
Almost All

Maternally inherited cytoplasmic bacteria have occasionally been observed in embryos and adults of different strains of several Drosophila species. While there is a considerable body of data on the relationship between bacteria and embryo viability, little is known about the behavior of these bacteria during the early development of Drosophila. In eggs laid by infected Drosophila melanogaster females we showed that cytoplasmic bacteria were initially concentrated in a thin cortical layer and scattered in the yolk region. During the following syncytial blastoderm mitoses the bacteria mainly accumulated towards the poles of the mitotic spindles, suggesting that astral microtubules play a role in localizing bacteria. This is supported by the observation that treatment of the infected embryos with the microtubule-disrupting drug colchicine led to the partial dissociation of the bacteria from the spindle poles, whereas cytochalasin treatment left almost all the bacterial clusters intact. Moreover, bacteria were not found near the polar bodies and yolk nuclei, which were without astral microtubules. In mitosis-defective embryos, with centrosomes dissociated from the nuclei, the bacteria were concentrated in association with the isolated astral microtubules, and in cold-treated embryos, in which microtubules regrew from isolated centrosomes after recovering, the bacteria clustered around the newly formed asters. These observations, also supported by electron microscope analysis, indicate a close relationship between cytoplasmic bacteria and astral microtubules, and suggest that the latter were able to build discrete cytoplasmic domains ensuring the proper distribution of cytoplasmic components during the blastoderm mitoses, despite the lack of cell membranes.

Cytological characterisation of the mutant phenotypes produced during early embryogenesis by null and loss-of-function alleles of the gammaTub37C gene in Drosophila

1999 ◽  
Vol 112 (5) ◽  
pp. 659-667 ◽  
Author(s):  
S. Llamazares ◽  
G. Tavosanis ◽  
C. Gonzalez
Keyword(s):  
Polar Body ◽  
Nuclear Proliferation ◽  
Early Embryogenesis ◽  
Drosophila Embryo ◽  
Loss Of Function ◽  
Female Meiosis ◽  
Polar Bodies ◽  
Early Drosophila Embryo ◽  
Gamma Tubulin ◽  
Mutant Phenotypes

We have studied the mutant phenotypes brought about during early embryogenesis by mutation in the gammaTub37C gene, one of the two isoforms of gamma-tubulin that have been identified in Drosophila. We have focused our attention on fs(2)TW1(1) and fs(2)TW1(RU34), a null and a hypomorph allele of this gene, whose sequences we report in this work. We have found that the abnormal meiotic figures observed in mutant stage 14 oocytes are not observed in laid oocytes or fertilised embryos, suggesting that these abnormal meiotic figures are not terminally arrested. We have also concluded that both null and hypomorph alleles lead to a total arrest of nuclear proliferation during early embryogenesis. This is in contrast to their effect on female meiosis-I where hypomorph alleles display a much weaker phenotype. Finally, we have observed that null and hypomorph alleles lead to some distinct phenotypes. Unfertilised laid oocytes and fertilised embryos deficient for gammaTub37C do not contain polar bodies and have a few bipolar microtubule arrays. In contrast, oocytes and embryos from weaker alleles do not have these microtubule arrays, but do contain polar bodies, or polar-body-like structures. These results indicate that gammaTub37C is essential for nuclear proliferation in the early Drosophila embryo.

scholarly journals Assembly of yolk spindles in the early Drosophila embryo

2003 ◽  
Vol 120 (4) ◽  
pp. 441-454 ◽  
Author(s):  
Maria Giovanna Riparbelli ◽  
Giuliano Callaini
Keyword(s):  
Drosophila Embryo ◽  
Early Drosophila Embryo

Resolving the Lourinia armata (Claus, 1866) complex with remarks on the monophyletic status of Louriniidae, Monard 1927 (Copepoda: Harpacticoida)

Zootaxa ◽  
2021 ◽  
Vol 5051 (1) ◽  
pp. 346-386
Author(s):  
SÜPHAN KARAYTUĞ ◽  
SERDAR SAK ◽  
ALP ALPER ◽  
SERDAR SÖNMEZ
Keyword(s):  
Comparative Evaluation ◽  
Species Complex ◽  
Detailed Examination ◽  
The Other ◽  
Phylogenetic Position ◽  
Nicobar Island ◽  
Other Hand ◽  
The Family ◽  
Close Relationship ◽  
Almost All

An attempt was made to test if Lourinia armata (Claus, 1866)—as it is currently diagnosed—represents a species complex. Detailed examination and comparisons of several specimens collected from different localities suggest that L. armata indeed represents a complex of four closely related morphospecies that can be differentiated from one another by only detailed observations. One of the four species is identified as Lourinia aff. armata and the other three species are described as new to science and named as Lourinia wellsi sp. nov., L. gocmeni sp. nov., and L. aldabraensis sp. nov. Detailed review of previous species records indicates that the genus Lourinia Wilson, 1924 is distributed worldwide. Ceyloniella nicobarica Sewell, 1940, originally described from Nicobar Island and previously considered a junior subjective synonym of L. armata is reinstated as Lourinia nicobarica (Sewell, 1940) comb. nov. on the basis of the unique paddle-shaped caudal ramus seta V. It is postulated that almost all of these records are unreliable in terms of representing true Lourinia aff. armata described herein. On the other hand, the comparative evaluation of the illustrations and descriptions in the published literature indicates the presence of several new species waiting to be discovered in the genus Lourinia.                 It has been determined that, according to updated modern keys, the recent inclusion of the monotypic genus Archeolourinia Corgosinho & Schizas, 2013 in the Louriniidae is not justified since Archeolourinia shermani Corgosinho & Schizas, 2013 does not belong to this family but should be assigned to the Canthocamptidae. On the other hand, it has been argued that the exact phylogenetic position of the Louriniidae still remains problematic since none of the diagnostic characters supports the monophyly of the family within the Oligoarthra. It has also been argued that the close relationship between Louriniidae and Canthocamptidae is supported since both families share the homologous sexual dimorphism (apophysis) on P3 endopod. The most important characteristic that can possibly be used to define Louriniidae is the reduction of maxilliped.  

scholarly journals The GAGA factor is required in the early Drosophila embryo not only for transcriptional regulation but also for nuclear division

Development ◽  
1996 ◽  
Vol 122 (4) ◽  
pp. 1113-1124 ◽  
Author(s):  
K.M. Bhat ◽  
G. Farkas ◽  
F. Karch ◽  
H. Gyurkovics ◽  
J. Gausz ◽  
...  
Keyword(s):  
Gene Expression ◽  
Chromatin Remodeling ◽  
In Vitro Transcription ◽  
Drosophila Embryo ◽  
Gaga Factor ◽  
Early Drosophila Embryo ◽  
Hypersensitive Sites ◽  
And Function ◽  
Stimulatory Factor

The GAGA protein of Drosophila was first identified as a stimulatory factor in in vitro transcription assays using the engrailed and Ultrabithorax promoters. Subsequent studies have suggested that the GAGA factor promotes transcription by blocking the repressive effects of histones; moreover, it has been shown to function in chromatin remodeling, acting together with other factors in the formation of nuclease hypersensitive sites in vitro. The GAGA factor is encoded by the Trithorax-like locus and in the studies reported here we have used the maternal effect allele Trl13C to examine the functions of the protein during embryogenesis. We find that GAGA is required for the proper expression of a variety of developmental loci that contain GAGA binding sites in their upstream regulatory regions. The observed disruptions in gene expression are consistent with those expected for a factor involved in chromatin remodeling. In addition to facilitating gene expression, the GAGA factor appears to have a more global role in chromosome structure and function. This is suggested by the spectrum of nuclear cleavage cycle defects observed in Trl13C embryos. These defects include asynchrony in the cleavage cycles, failure in chromosome condensation, abnormal chromosome segregation and chromosome fragmentation. These defects are likely to be related to the association of the GAGA protein with heterochromatic satellite sequences which is observed throughout the cell cycle.

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