Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Researchers find gland that tells fruit flies when to stop growing

25.10.2005


Many baffled parents have wondered whether their teenagers would ever stop growing. The answer is obvious, but researchers have never really quite understood just how an organism determines when it has reached its optimal size and growth should cease.


Photo credit: Christen Mirth
A normal fruit fly in the pupa stage of development (left) lies next to one in which growth has been inhibited by an artificially enlarged prothoracic gland.



Now University of Washington biologists studying the physiology of Drosophila melanogaster, the common fruit fly, have discovered an organ that assesses the size of the juvenile and signals when it has reached a critical weight to begin metamorphosis into an adult.

The team, led by postdoctoral researcher Christen Mirth, found that the prothoracic gland, a major endocrine organ situated just in front of the brain, assesses the fly’s size as it grows during the larval stage. The gland then sends hormonal signals when it senses the fly has reached a size appropriate to enter adulthood.


The scientists found they could use the pathway that sends insulin to a fly’s cells to genetically manipulate the size of the prothoracic gland, part of a more complex structure called the ring gland, and send false signals about a fly’s weight. Enlarging the gland by increasing insulin signaling triggered metamorphosis at smaller sizes than usual. Suppressing the gland’s growth by decreasing insulin signaling allowed larvae to grow larger than usual before entering the pupal stage that precedes adulthood.

Mirth and her colleagues, UW biology professors Lynn Riddiford and James Truman, surmised that size assessment had to be accomplished through a major endocrine organ, so they screened all fruit fly endocrine glands, enlarging or reducing them and studying the effect on body size.

"The only thing that gave us the size shifts that we had hypothesized was changing the size of the prothoracic gland. Enlarging the organ made the animals small, and vice versa," Mirth said. "It seems to be a nutrition-related phenomenon. You sort of trick the fruit fly into thinking it is bigger than it really is."

Enlarging the prothoracic gland produces much smaller-than-normal adult fruit flies, Riddiford said. "In humans, it would be as if you reached puberty when you were 6 years old."

In the research, Mirth determined the critical weight for fruit flies to begin metamorphosis, and examined when larvae with enlarged prothoracic glands reached that weight compared with normal larvae. This was done by starving larvae of known weight and age, then determining what proportion of them reached metamorphosis.

She found that larvae with enlarged prothoracic glands reached critical weight earlier and at a much smaller size than normal larvae. But she also found that flies with enlarged glands reached that critical weight and initiated metamorphosis before they had reached a size that would allow them to survive metamorphosis. Suppressing prothoracic gland growth by reducing insulin signaling caused flies to spend longer in each stage of development, allowing them to be larger than normal when they emerged into adulthood.

"Normal larvae would never initiate metamorphosis before they were of a sufficient size to survive the process," Mirth said.

This marks the first time a tissue such as the prothoracic gland has been found to be a factor in size assessment, she said, and it provides a more complete picture of how an organism’s growth is controlled.

Mirth is lead author of the work, which is published in the Oct. 25 edition of the journal Current Biology and was funded by the UW Royalty Research Fund.

"What is particularly exciting about these findings is that now that we know how size is assessed in Drosophila larvae, we can begin examining other species for analogous structures," she said.

The primary goal of the research, conducted in Riddiford’s and Truman’s laboratories, is to get a fuller understanding of an organism’s growth process. Scientists have had a fairly good understanding of how growth is regulated by environmental factors such as nutrition, but the new research clarifies the second part of the picture – how an organism knows that growth should stop.

"There has to be a way for an animal to assess its size, and I don’t think it does it by looking in the mirror," Riddiford said.

Vince Stricherz | EurekAlert!
Further information:
http://www.washington.edu

More articles from Life Sciences:

nachricht The interactome of infected neural cells reveals new therapeutic targets for Zika
23.01.2017 | D'Or Institute for Research and Education

nachricht Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Quantum optical sensor for the first time tested in space – with a laser system from Berlin

For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.

According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...

Im Focus: Traffic jam in empty space

New success for Konstanz physicists in studying the quantum vacuum

An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Sustainable Water use in Agriculture in Eastern Europe and Central Asia

19.01.2017 | Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

 
Latest News

New technology for mass-production of complex molded composite components

23.01.2017 | Process Engineering

Quantum optical sensor for the first time tested in space – with a laser system from Berlin

23.01.2017 | Physics and Astronomy

The interactome of infected neural cells reveals new therapeutic targets for Zika

23.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>