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

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.

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

Journal of Cell Science ◽

10.1242/jcs.107.3.673 ◽

1994 ◽

Vol 107 (3) ◽

pp. 673-682 ◽

Cited By ~ 3

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.

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Drosophila-Raf Acts to Elaborate Dorsoventral Pattern in the Ectoderm of Developing Embryos

Genetics ◽

10.1093/genetics/159.3.1031 ◽

2001 ◽

Vol 159 (3) ◽

pp. 1031-1044

Author(s):

Kori Radke ◽

Kimberly Johnson ◽

Rong Guo ◽

Anne Davidson ◽

Linda Ambrosio

Keyword(s):

Egf Receptor ◽

Drosophila Embryo ◽

Functional Requirements ◽

Loss Of Function ◽

Maternal Role ◽

Partial Loss ◽

Cell Fates ◽

Regulatory Domains ◽

Early Drosophila Embryo ◽

Lateral Cell

Abstract In the early Drosophila embryo the activity of the EGF-receptor (Egfr) is required to instruct cells to adopt a ventral neuroectodermal fate. Using a gain-of-function mutation we showed that D-raf acts to transmit this and other late-acting embryonic Egfr signals. A novel role for D-raf was also identified in lateral cell development using partial loss-of-function D-raf mutations. Thus, we provide evidence that zygotic D-raf acts to specify cell fates in two distinct pathways that generate dorsoventral pattern within the ectoderm. These functional requirements for D-raf activity occur subsequent to its maternal role in organizing the anterioposterior axis. The consequences of eliminating key D-raf regulatory domains and specific serine residues in the transmission of Egfr and lateral epidermal signals were also addressed here.

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Alternative linker histone permits fast paced nuclear divisions in early Drosophila embryo

Nucleic Acids Research ◽

10.1093/nar/gkaa624 ◽

2020 ◽

Vol 48 (16) ◽

pp. 9007-9018

Author(s):

László Henn ◽

Anikó Szabó ◽

László Imre ◽

Ádám Román ◽

Andrea Ábrahám ◽

...

Keyword(s):

Low Temperature ◽

Early Embryo ◽

Linker Histone ◽

Early Embryogenesis ◽

Drosophila Embryo ◽

Core Histone ◽

Early Embryos ◽

Early Drosophila Embryo ◽

Nucleosome Stability

Abstract In most animals, the start of embryogenesis requires specific histones. In Drosophila linker histone variant BigH1 is present in early embryos. To uncover the specific role of this alternative linker histone at early embryogenesis, we established fly lines in which domains of BigH1 have been replaced partially or completely with that of H1. Analysis of the resulting Drosophila lines revealed that at normal temperature somatic H1 can substitute the alternative linker histone, but at low temperature the globular and C-terminal domains of BigH1 are essential for embryogenesis. In the presence of BigH1 nucleosome stability increases and core histone incorporation into nucleosomes is more rapid, while nucleosome spacing is unchanged. Chromatin formation in the presence of BigH1 permits the fast-paced nuclear divisions of the early embryo. We propose a model which explains how this specific linker histone ensures the rapid nucleosome reassembly required during quick replication cycles at the start of embryogenesis.

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The Tailless Nuclear Receptor Acts as a Dedicated Repressor in the Early Drosophila Embryo

Molecular and Cellular Biology ◽

10.1128/mcb.26.9.3446-3454.2006 ◽

2006 ◽

Vol 26 (9) ◽

pp. 3446-3454 ◽

Cited By ~ 35

Author(s):

Érica Morán ◽

Gerardo Jiménez

Keyword(s):

Nuclear Receptors ◽

Nuclear Receptor ◽

Target Genes ◽

Activation Function ◽

Drosophila Embryo ◽

Intact Protein ◽

Positive Interactions ◽

Orphan Nuclear Receptor ◽

Loss Of Function ◽

Early Drosophila Embryo

ABSTRACT Tailless is an orphan nuclear receptor that controls terminal body patterning in Drosophila. Genetic analyses have revealed both positive and negative regulatory interactions of Tailless with various target genes, leading to the idea that, like many other nuclear receptors, Tailless mediates both activation and repression of transcription. In this paper, we have examined the consequences of converting Tailless into an obligate repressor and compared the activities of the resulting protein with those of wild-type Tailless. We find that this repressor form of Tailless behaves like the intact protein in gain- and loss-of-function experiments, being sufficient to support normal embryonic development and establish accurate patterns of gene expression even for positive Tailless targets such as hunchback and brachyenteron. This suggests that Tailless functions exclusively as a transcriptional repressor in the embryo and that the observed positive interactions of Tailless with specific targets are secondary effects involving repression of repressors. We provide evidence that knirps is one such repressor gene acting between Tailless and its indirect positive targets. Finally, our results indicate that Tailless exerts an active mechanism of repression via its ligand-binding domain and that this activity is largely independent of the activation function 2 (AF2) motif characteristic of most nuclear receptors.

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Faculty Opinions recommendation of Establishment of developmental precision and proportions in the early Drosophila embryo.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1004171.48106 ◽

2002 ◽

Author(s):

Patricia Simpson

Keyword(s):

Drosophila Embryo ◽

Early Drosophila Embryo

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Faculty Opinions recommendation of Nucleosomal histone kinase-1 phosphorylates H2A Thr 119 during mitosis in the early Drosophila embryo.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1019090.214588 ◽

2004 ◽

Author(s):

Fyodor Urnov

Keyword(s):

Drosophila Embryo ◽

Early Drosophila Embryo ◽

Histone Kinase ◽

Nucleosomal Histone

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Faculty Opinions recommendation of Model for the robust establishment of precise proportions in the early Drosophila embryo.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1031796.367912 ◽

2006 ◽

Author(s):

Hans van Beek

Keyword(s):

Drosophila Embryo ◽

Early Drosophila Embryo

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MATERNAL-ZYGOTIC GENE INTERACTIONS DURING FORMATION OF THE DORSOVENTRAL PATTERN IN DROSOPHILA EMBRYOS

Genetics ◽

10.1093/genetics/105.3.615 ◽

1983 ◽

Vol 105 (3) ◽

pp. 615-632 ◽

Cited By ~ 1

Author(s):

Pat Simpson

Keyword(s):

Early Embryo ◽

Drosophila Embryo ◽

Sensitive Period ◽

Temperature Sensitive ◽

Mutant Genotype ◽

Dominant Phenotype ◽

Zygotic Gene ◽

Definition Of ◽

Mutant Phenotypes ◽

Dominant Lethality

ABSTRACT Maternal-zygotic interactions involving the three genes dorsal (dl), twist (twi) and snail (sna) are described. The results suggest that all three are involved in the process by which the dorsoventral pattern of the Drosophila embryo is established. First, the lethal embryonic mutant phenotypes are rather similar. In homozygous twi or sna embryos invagination of the ventral presumptive mesodermal cells fails to occur, and the resulting embryos are devoid of internal organs. This is very similar to the dominant phenotype described for dl; in the case of dl, however, the effect is a maternal one dependent on the mutant genotype of the female. Second, a synergistic interaction has been found whereby dominant lethality of twi - or sna-bearing zygotes is observed in embryos derived from heterozygous dl females at high temperature. The temperature sensitivity of this interaction permitted definition of a temperature-sensitive period which is probably that of dl. This was found to extend from approximately 12 hr prior to oviposition to 2— 3 hr of embryogenesis. A zygotic action for the dl gene in addition to the maternal effect was revealed by the finding that extra doses of dl + in the zygotes can partially rescue the dominant lethality of heterozygous twi embryos derived from heterozygous dl females. Two possible interpretations of the synergism are considered: (1) twi and sna are activated in the embryos as a result of positional signals placed in the egg as a consequence of the functioning of the dl gene during oogenesis and, thus, play a role in embryonic determination. (2) The gene products of dl + and twi + (or sna +) combine to produce a functional molecule that is involved in the specification of dorsoventral pattern in the early embryo.

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