Featured Research

from universities, journals, and other organizations

Researchers Find Gland That Tells Fruit Flies When To Stop Growing

Date:
October 25, 2005
Source:
University of Washington
Summary:
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. 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.

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.
Credit: Photo credit: Christen Mirth

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.

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.


Story Source:

The above story is based on materials provided by University of Washington. Note: Materials may be edited for content and length.


Cite This Page:

University of Washington. "Researchers Find Gland That Tells Fruit Flies When To Stop Growing." ScienceDaily. ScienceDaily, 25 October 2005. <www.sciencedaily.com/releases/2005/10/051025074024.htm>.
University of Washington. (2005, October 25). Researchers Find Gland That Tells Fruit Flies When To Stop Growing. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2005/10/051025074024.htm
University of Washington. "Researchers Find Gland That Tells Fruit Flies When To Stop Growing." ScienceDaily. www.sciencedaily.com/releases/2005/10/051025074024.htm (accessed July 31, 2014).

Share This




More Plants & Animals News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Concern Grows Over Worsening Ebola Crisis

Concern Grows Over Worsening Ebola Crisis

AFP (July 30, 2014) Pan-African airline ASKY has suspended all flights to and from the capitals of Liberia and Sierra Leone amid the worsening Ebola health crisis, which has so far caused 672 deaths in Guinea, Liberia and Sierra Leone. Duration: 00:43 Video provided by AFP
Powered by NewsLook.com
At Least 20 Chikungunya Cases in New Jersey

At Least 20 Chikungunya Cases in New Jersey

AP (July 30, 2014) At least 20 New Jersey residents have tested positive for chikungunya, a mosquito-borne virus that has spread through the Caribbean. (July 30) Video provided by AP
Powered by NewsLook.com
Xtreme Eating: Your Daily Caloric Intake All On One Plate

Xtreme Eating: Your Daily Caloric Intake All On One Plate

Newsy (July 30, 2014) The Center for Science in the Public Interest released its 2014 list of single meals with whopping calorie counts. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins