Navigation Links
Molecular evolution of genetic sex-determination switch in honeybees

It's taken nearly 200 years, but scientists in Arizona and Europe have teased out how the molecular switch for sex gradually and adaptively evolved in the honeybee.

The first genetic mechanism for sex determination was proposed in the mid-1800s by a Silesian monk named Johann Dzierson, according to the study's co-author and Arizona State University Provost Robert E. Page Jr. Dzierson was trying to understand how males and females were produced in honey bee colonies. He knew that the difference between queen and worker bees both females emerged from the different quality and quantity of food. But, what about the males, he asked.

Dzierson posited that males were haploid possessing one set of chromosomes, which was confirmed in the 1900s with the advent of the microscope. Under the magnifying lens, researchers could see that eggs that gave rise to drones were not penetrated by sperm. However, how this system of haplodiploid sex determination ultimately evolved at a molecular level has remained one of the most important questions in developmental genetics.

In the December issue of Current Biology, Page and Martin Beye, lead author and professor with the Institute of Evolutionary Genetics in the University of Duesseldorf, Germany, and their collaborators laid out the final pieces of how these systems evolved in their article "Gradual molecular evolution of a sex determination switch in honeybees through incomplete penetrance of femaleness."

The authors studied 14 natural sequence variants of the complementary sex determining switch (csd gene), for 76 genotypes of honey bees.

While complex, the researchers had several tools at hand that their predecessors lacked to solve this sexual determination puzzle. First, honey bees are ideal study subjects because they have one gene locus responsible for sex determination. Also, Page and former graduate student Greg Hunt identified genetic markerswell-characterized regions of DNAclose to the complementary sex determining locus to allow gene mapping. In addition, Hunt and Page found that the honey bees' high recombination ratethe process by which genetic material is physically mixed during sexual reproductionis the highest of any known animal studied, which helped Beye isolate, sequence and characterize the complementary sex determining locus. Page and Beye were also able to knock out an allele and show how one could get a male from a diploid genotype; work that was featured on the cover of the journal Cell in 2003.

However, the questions of which alleles were key, how they worked together and in what combinations and why this system evolved were left unanswered, though tantalizing close. This compelled the current team of collaborators to step back to review what actually constitutes an allele.

"There has to be some segment of that gene that is responsible in this allelic series, where if you have two different coding sequences in that part of the gene you end up producing a female," said Page, who is also the Foundation Chair of Life Sciences at ASU. "So we asked how different do two alleles have to be? Can you be off one or two base pairs or does it always have to be the same set of sequences? We came up with a strategy to go in and look at these 18-20 alleles and find out what regions of these genes are responsible among these variants."

"In this process, we also had to determine if there are intermediate kinds of alleles and discover how they might have evolved," said Page.

What the authors found was that at least five amino acid differences can control allelic differences to create femaleness through the complementary sex determiner (csd) genethe control switch.

"We discovered that different amounts of arginine, serine and proline affect protein binding sites on the csd gene, which in turn lead to different conformational states, which then lead to functional changes in the beesthe switch that determines the shift from female to not female," said Page.

The authors also discovered a natural evolutionary intermediate that showed only three amino acid differences spanned the balance between lethality and induced femaleness. These findingswhich have taken nearly 200 years of study to pin downsuggested that incomplete penetrance may be the mechanism by which new molecular switches can gradually and adaptively evolve.

In addition to Beye and Page, authors included Christine Seelmann and Tanja Gempe with the University of Duesseldorf, Martin Hasslemann with the Institute of Genetics at the University of Cologne in Germany, Xavier Bekmans with Universit Lille in France and Kim Fondrk with Arizona State University. The work was supported by grants from the Deutsche Forschungsgemeinschaft.

Provost Page is the Foundation Chair of Life Sciences at ASU, a professor in the School of Life Sciences and the author of "The Spirit of the Hive: The mechanism of social evolution" published by Harvard University Press in 2013.


Contact: Margaret Coulombe
Arizona State University

Related biology news :

1. Molecular markers used for assessment of early sciatic nerve injury
2. A wrong molecular turn leads down the path to Type 2 diabetes
3. Uncovering first molecular missteps that drive neurons in pathway leading to Alzheimers disease
4. UI researcher studies evolution on the molecular level
5. Molecular interplay explains many immunodeficiencies
6. The Association for Molecular Pathology announces highlights of Phoenix meeting
7. Penn researchers identify molecular link between gut microbes and intestinal health
8. Singapore scientists expose molecular secrets of bile duct cancers from different countries
9. Molecular Velcro may lead to cost-effective alternatives to natural antibodies
10. Grafted limb cells acquire molecular fingerprint of new location, UCI study shows
11. Molecular biology: Designer of protein factories exposed
Post Your Comments:
Related Image:
Molecular evolution of genetic sex-determination switch in honeybees
(Date:6/2/2016)... 2016 Perimeter Surveillance & Detection ... Physical Infrastructure, Support & Other Service  The ... offers comprehensive analysis of the global Border Security ... revenues of $17.98 billion in 2016. Now: ... leader in software and hardware technologies for advanced video ...
(Date:5/20/2016)... , May 20, 2016  VoiceIt is excited ... with VoicePass. By working together, VoiceIt ...  Because VoiceIt and VoicePass take slightly different approaches ... increases both security and usability. ... about this new partnership. "This marketing ...
(Date:5/9/2016)... Elevay is currently known as ... for high net worth professionals seeking travel for work ... world, there is still no substitute for a face-to-face ... your deal with a firm handshake. This is why ... of citizenship via investment programs like those offered by ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... Houston Methodist Willowbrook Hospital has signed ... to serve as their official health care provider. ... will provide sponsorship support, athletic training services, and ... volunteers, athletes and families. "We are ... and to bring Houston Methodist quality services and ...
(Date:6/23/2016)... , June 23, 2016   EpiBiome , a ... $1 million in debt financing from Silicon Valley Bank ... automation and to advance its drug development efforts, as ... facility. "SVB has been an incredible strategic ... services a traditional bank would provide," said Dr. ...
(Date:6/23/2016)... , June 23, 2016 Apellis Pharmaceuticals, ... 1 clinical trials of its complement C3 inhibitor, ... and multiple ascending dose studies designed to assess ... of subcutaneous injection in healthy adult volunteers. ... either as a single dose (ranging from 45 ...
(Date:6/23/2016)... ... June 23, 2016 , ... ClinCapture, the only free ... and will showcase its product’s latest features from June 26 to June 30, ... poster on Disrupting Clinical Trials in The Cloud during the conference. DIA ...
Breaking Biology Technology: