Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Insects that produce males from unfertilized eggs reveal a surprising cellular feat

19.04.2006
Scientists have long known that the social insects in the order Hymenoptera--which includes ants, bees, and wasps--have an unusual mechanism for sex determination: Unfertilized eggs develop into males, while fertilized eggs become females. But the development of an unfertilized egg into an adult (called parthenogenesis) remains a mysterious process.

One mystery has been the origin of the centrosome, an essential cellular component that is ordinarily derived from the sperm after fertilization. A new study led by researchers at the University of California, Santa Cruz, describes a remarkable process by which the egg cells of Hymenopteran insects make new centrosomes from scratch. The process involves enigmatic cellular structures called accessory nuclei, the function of which has not been explained since they were first discovered in the 1960s.

"Centrosomes arise from other centrosomes through duplication, but there is no centrosome in the egg that could give rise to new ones. We found that the accessory nuclei seed the formation of new centrosomes in unfertilized eggs," said Patrick Ferree, a graduate student in molecular, cell, and developmental biology at UCSC.

Ferree is first author of a paper describing the new findings in the April 18 issue of the journal Current Biology. Coauthor William Sullivan, professor of molecular, cell, and developmental biology at UCSC, said the findings have implications for understanding basic cell biology, the evolution of Hymenopteran insects, and centrosomal anomalies in cancer cells. The study also shows just how much remains to be discovered about the diversity of life at the cellular level, he said.

"You would think we’d have identified all the structures in the cell by now, but 90 percent of the material in cell biology textbooks comes from research on nine or ten organisms," Sullivan said. "Every time I look at a honeybee now, I think about these amazing structures they have, and it implies that among the millions of other species there must be cellular mechanisms we haven’t even imagined."

Centrosomes help orchestrate cell division, building an apparatus of microtubules called the mitotic spindle, which pulls apart the duplicated chromosomes so that each of the two daughter cells gets a complete set of chromosomes. The centrosome contains about a hundred different proteins, including the main protein for making microtubules, called gamma tubulin.

The UCSC researchers studied the development of centrosomes in the eggs of two parasitic wasps (Nasonia vitripennis and Muscidifurax uniraptor). Using fluorescently labeled antibodies that recognize and bind to gamma tubulin and other centrosomal proteins, they demonstrated the presence of these proteins in accessory nuclei and showed that the accessory nuclei appear to give rise to centrosomes.

Accessory nuclei bud off from the membrane of the nucleus, the cellular structure that contains the chromosomes. By the time the egg is fully developed, it contains several hundred accessory nuclei that look much like the nucleus except that they don’t contain chromosomes. Late in the development of the egg cell, the accessory nuclei disintegrate and centrosomes appear in the same locations in the cell.

"Right before the egg is laid, the membranes of the accessory nuclei break down, and at the same time the centrosomes begin to form," Ferree said.

One of the most striking aspects of this mechanism is the large number of accessory nuclei and centrosomes that form in the developing eggs of these Hymenopteran insects.

"You only need two centrosomes, and they make hundreds of them. So they go through a lot of work to make a male," Sullivan said. "A lot of energy goes into making these centrosomes, and if the egg gets fertilized they don’t use them--the centrosome from the sperm is used preferentially."

Centrosomes remain somewhat mysterious structures, Ferree said, but researchers may be able to learn more about them by purifying accessory vesicles and studying their protein components.

Accessory nuclei have been observed in other species besides Hymenopteran insects, and they may have other functions in addition to making centrosomes, he said. They may also hold clues to the evolutionary origin of the Hymenoptera. Because the males of these insects develop from unfertilized eggs, they have half the number of chromosomes that females have--in technical terms, the males are haploid and the females are diploid.

This situation, known as haplodiploidy, results in interesting genetic relationships that are thought to underlie the complex social behavior of Hymenopteran insects. One of the key steps in the evolution of social insects, therefore, may have been the development of a mechanism for making centrosomes from scratch.

"The Hymenoptera were probably derived from a species that had accessory nuclei, and in the evolution of haplodiploidy the accessory nuclei were co-opted as a way of building centrosomes," Sullivan said.

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>