- Reciprocal inheritance of centrosomes in the parthenogenetic Hymenopteran Nasonia vitripennis
Current Biology, Volume 10, Issue 22, 14 November 2000, Pages 1413-1419
Uyen Tram and William Sullivan
SummaryBackground: In the majority of animals, the centrosome—the microtubule-organizing center of the cell—is assembled from components of both the sperm and the egg. How the males of the insect order Hymenoptera acquire centrosomes is a mystery, as they originate from virgin birth.Results: To address this issue, we observed centrosome, spindle and nuclear behavior in real time during early development in the parthenogenetic hymenopteran Nasonia vitripennis. Female meiosis was identical in unfertilized eggs. Centrosomes were assembled before the first mitotic division but were inherited differently in unfertilized and fertilized eggs. In both, large numbers of asters appeared at the cortex of the egg after completion of meiosis. In unfertilized eggs, the asters migrated inwards and two of them became stably associated with the female pronucleus and the remaining cytoplasmic asters rapidly disappeared. In fertilized eggs, the Nasonia sperm brought in paternally derived centrosomes, similar to Drosophila melanogaster. At pronuclear fusion, the diploid zygotic nucleus was associated only with paternally derived centrosomes. None of the cytoplasmic asters associated with the zygotic nucleus and, as in unfertilized eggs, they rapidly degenerated.Conclusions: Selection and migration of the female pronucleus is independent of the sperm and its aster. Unfertilized male eggs inherit maternal centrosomes whereas fertilized female eggs inherit paternal centrosomes. This is the first system described in which centrosomes are reciprocally inherited. The results suggest the existence of a previously undescribed mechanism for regulating centrosome number in the early embryo.
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- Dominant-negative mutant dynein allows spontaneous centrosome assembly, uncouples chromosome and cen...
Current Biology, Volume 11, Issue 2, 23 January 2001, Pages 136-140
István Belecz, Cayetano Gonzalez, Jaakko Puro and János Szabad
SummaryCleavage cycles commence and chromosome and centrosome cycles proceed in harmony following fertilization of Drosophila eggs and completion of the meiotic divisions []. The sperm-introduced centrioles replicate, separate, and while recruit pericentriolar material centrosomes (CS) form []. The CS nucleate asters of microtubules (MT). Spindles form following interaction of some astral MT with kinetochores. In unfertilized eggs, chromosomes do not replicate, and CS and MT asters never form, although their components are present in the egg cytoplasm []; unknown mechanisms prevent chromosome replication and CS and MT assembly. In unfertilized LaborcD eggs, rudimentary CS assemble spontaneously and instantaneously and nucleate small MT asters. In fertilized LaborcD eggs, normal CS form and organize normal asters. However, the CS replicate prior to accomplishment of the first mitosis, and spindles with multiple CS develop. In fertilized LaborcD eggs, while the chromosome cycles cease, CS cycles proceed as in wild type. Knowing that LaborcD is a dominant-negative mutation and encodes the formation of mutant cytoplasmic dynein heavy chain molecules, we show here that cytoplasmic dynein [] is involved in prevention of CS assembly in unfertilized eggs and establishing harmony between the chromosome and the CS cycles.
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- A Bacterium Targets Maternally Inherited Centrosomes to Kill Males in Nasonia
Current Biology, Volume 18, Issue 18, 23 September 2008, Pages 1409-1414
Patrick M. Ferree, Amanda Avery, Jorge Azpurua, Timothy Wilkes and John H. Werren
SummaryMale killing is caused by diverse microbial taxa in a wide range of arthropods [1,2,3,4,5,6,7]. This phenomenon poses important challenges to understanding the dynamics of sex ratios and host-pathogen interactions. However, the mechanisms of male killing are largely unknown. Evidence from one case in Drosophila suggests that bacteria can target components of the male-specific sex-determination pathway . Here, we investigated male killing by the bacterium Arsenophonus nasoniae in the haplo-diploid wasp Nasonia vitripennis, in which females develop as diploids from fertilized eggs and males develop parthenogenetically as haploids from unfertilized eggs. We found that Arsenophonus inhibits the formation of maternal centrosomes, organelles required specifically for early male embryonic development [9,10,11], resulting in unorganized mitotic spindles and developmental arrest well before the establishment of somatic sexual identity. Consistent with these results, rescue of Arsenophonus-induced male lethality was achieved by fertilization with sperm bearing the supernumerary chromosome paternal sex ratio (PSR) , which destroys the paternal genome but bypasses the need for maternal centrosomes by allowing transmission of the sperm-derived centrosome into the egg. These findings reveal a novel mechanism of male killing in Nasonia, demonstrating that bacteria have evolved different mechanisms for inducing male killing in the Arthropods.
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Copyright © 1980 All rights reserved.
Cell, Volume 22, Issue 1, 119-126, 1 November 1980
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Association of a 5S gene transcription factor with 5S RNA and altered levels of the factor during cell differentiation
Barry M. Honda and Robert G. Roeder
- We have previously purified from Xenopus ovaries a protein factor (TF IIIA) which is necessary for the accurate in vitro transcription of 5S RNA genes. We now report that this factor (a 5S gene transcription effector) is identical by immunological, chemical and functional criteria to the protein associated with 5S RNA (the gene product) as a 7S ribonucleo-protein (RNP) complex in immature oocytes. After oocyte maturation, TF IIIA is no longer detectable functionally or immunologically in unfertilized eggs, which do not synthesize 5S RNA in vitro. Moreover, we cannot detect TF IIIA immunologically in extracts from Xenopus somatic cells which, nevertheless, efficiently transcribe 5S genes.