Navigation Links
Researchers now able to look deep into heart to view triggers of a heart's beat

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, bu t 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.


Source:University of Pittsburgh Medical Center

Related biology news :

1. Researchers discover way to make cells in the eye sensitive to light
2. Researchers find how protein allows insects to detect and respond to pheromones
3. Researchers Uncover Key Step In Manufacture of Memory Protein
4. Researchers reveal the infectious impact of salmon farms on wild salmon
5. Researchers identify target for cancer drugs
6. Researchers discover molecule that causes secondary stroke
7. Researchers find missing genes of ancient organism
8. Researchers trace evolution to relatively simple genetic changes
9. Researchers add new tool to tumor-treatment arsenal
10. UF Researchers Map Bacterial Proteins That Cause Tooth Loss
11. VCU Researchers Identify Networks Of Genes Responding To Alcohol In The Brain
Post Your Comments:

(Date:10/29/2015)... , Oct. 29, 2015   MedNet Solutions ... the entire spectrum of clinical research, is pleased to ... High Tech Association (MHTA) as one of only three ... the "Software – Small and Growing" category. The Tekne Awards ... who have shown superior technology innovation and leadership. ...
(Date:10/29/2015)... ANN ARBOR, Mich. , Oct. 29, 2015 ... with Eurofins Genomics for U.S. distribution of its ... DNA-seq kit and Rubicon,s new ThruPLEX Plasma-seq ... DNA to enable the preparation of NGS libraries ... in plasma for diagnostic and prognostic applications in ...
(Date:10/29/2015)... YORK , Oct. 29, 2015 ... technology, announced a partnership with 2XU, a global ... to deliver a smart hat with advanced bio-sensing ... and other athletes to monitor key biometrics to ... the strategic partnership, the two companies will bring together ...
Breaking Biology News(10 mins):
(Date:11/25/2015)... , November 25, 2015 ... Research Report is a professional and in-depth study ...      (Logo: ) , ... of the industry including definitions, classifications, applications and ... provided for the international markets including development trends, ...
(Date:11/24/2015)... ... ... The United States Golf Association (USGA) today announced Dr. Bruce Clarke, of ... since 1961, the USGA Green Section Award recognizes an individual’s distinguished service to the ... of Iselin, N.J., is an extension specialist of turfgrass pathology in the department of ...
(Date:11/24/2015)... 2015 /CNW/ - iCo Therapeutics ("iCo" or "the Company") ... for the quarter ended September 30, 2015. Amounts, ... and presented under International Financial Reporting Standards ("IFRS"). ... said Andrew Rae , President & CEO ... not only value enriching for this clinical program, ...
(Date:11/24/2015)... /PRNewswire/ - Aeterna Zentaris Inc. (NASDAQ:  AEZS) (TSX: AEZ) (the ... the Toronto Stock Exchange, confirms that as of the ... developments that would cause the recent movements in the ... --> About Aeterna Zentaris Inc. ... Aeterna Zentaris is a specialty biopharmaceutical company engaged in ...
Breaking Biology Technology: