Featured Research

from universities, journals, and other organizations

Blind flies without recycling: How Drosophila recovers the neurotransmitter histamine

Date:
March 18, 2013
Source:
Ruhr-Universitaet-Bochum
Summary:
In the fruit fly Drosophila, the functions of the three enzymes Tan, Ebony and Black are closely intertwined -- among other things they are involved in neurotransmitter recycling for the visual process. Researchers showed for the first time that flies cannot see without this recycling. Their analysis of the enzyme Black also raises new questions as to its function.

Three enzymes in the insect brain: A cross section of the lamina, the first switch point of the photoreceptor cells of Drosophila, shows the main extension of the photoreceptors surrounded by glial cells. The enzyme Tan (blue) is found in the photoreceptor extensions; Ebony (magenta) and Black (green) in the glial cells. The researchers stained the enzymes with antibodies.
Credit: Copyright Anna Ziegler, RUB, dissertation 2010

In the fruit fly Drosophila, the functions of the three enzymes Tan, Ebony and Black are closely intertwined -- among other things they are involved in neurotransmitter recycling for the visual process. RUB researchers from the Department of Biochemistry showed for the first time that flies cannot see without this recycling. Their analysis of the enzyme Black also raises new questions as to its function. Anna Ziegler, Florian Brüsselbach and Bernhard Hovemann report in the Journal of Comparative Neurology, which chose this topic as cover story.

Related Articles


Tan, Ebony and Black are important for the visual process and the formation of the cuticle

The fruit fly's genes tan, ebony and black contain the construction plans for three enzymes with the same names that work together in hardening the outer shell of the body, the cuticle. The same enzymes also occur in the compound eye of the fly. Researchers therefore assume that Tan, Ebony and Black work together in vision -- similar to the way they do in the formation of the cuticle. In fact, flies with mutations of the ebony and tan genes cannot see. A mutation of the black gene, however, has no such effect. Prof. Hovemann's team examined where the enzyme Black appears in the compound eye and the role it plays in vision.

Black and Ebony always occur together

First, the scientists tested where the genes ebony and black are active in the compound eye of the fruit fly and in its extra eyes on the head, the ocelli. They put different types of light-sensitive cells called photoreceptors, under the microscope. The result: both genes are always read together -- just like in the cuticle. This suggests that the functions of the enzymes Ebony and Black are closely linked.

Vision requires a continuous flow of the neurotransmitter histamine

When light falls into the compound eye, the photoreceptors release the neurotransmitter histamine. In previous studies, Bochum's biochemists already demonstrated that histamine is recycled via the glial cells surrounding the photoreceptors. There, the enzyme Ebony inactivates the neurotransmitter histamine by binding it to the amino acid ß-alanine, thus creating ß-alanyl-histamine. This molecule is transported from the glial cells back into the photoreceptors. Here, ß-alanine is split off again by the enzyme Tan, and histamine is produced. Previously, it was assumed that the enzyme Black is responsible for producing the ß-alanine, which is required for the inactivation of histamine. However, if a fly's eye has no functional Black, the visual process still runs normally. Hovemann's team therefore looked into the question of whether there is another supply route for ß-alanine. They also tested whether the fly eye can get around the recycling of histamine; this would be possible if the photoreceptors could directly reabsorb the released neurotransmitter, without it being inactivated in the glial cells.

No functioning sense of sight without histamine recycling

The researchers examined flies that were neither able to produce histamine themselves nor recycle it, because they lacked the enzyme for histamine synthesis and the enzyme Ebony. The team measured the flies' vision using so-termed electroretinography, which not only shows the excitation of the photoreceptor cells, but also the transmission of the signal to the brain. Even when the researchers added histamine from outside, the flies were blind. With this test, they showed for the first time that, for vision, Drosophila is dependent on the histamine recycling in the glial cells. Without recycling the enzyme Ebony, the cells in the insect eye cannot make any use of the neurotransmitter.

Flies can also see with disturbed ß-alanine production

Cells are not only able to produce ß-alanine with the aid of the enzyme Black, but also by converting the molecule uracil into ß-alanine using other enzymes. Hovemann's team inactivated both production pathways for ß-alanine and tested the vision of the fruit fly again. According to the electroretinogram, the animals' sense of sight was not impaired by the double mutation. "The results seem to represent a contradiction," says Bernhard Hovemann. "Although the insect eyes with the double mutation cannot produce ß-alanine, the animals seem to have normal vision. At the same time, our data clearly shows that the recycling by attaching ß-alanine is necessary for the animals to see." The researchers suggest that ß-alanine -- like histamine -- is recycled in a circuit between glial cells and photoreceptors. This would mean that the enzyme Black merely compensates for ß-alanine losses. "That would explain why we do not immediately find visual defects in flies which cannot produce new ß-alanine," says Hovemann. These puzzles can, however, only be solved by further studies.


Story Source:

The above story is based on materials provided by Ruhr-Universitaet-Bochum. Note: Materials may be edited for content and length.


Journal Reference:

  1. Anna B. Ziegler, Florian Brüsselbach, Bernhard T. Hovemann. Activity and coexpression ofDrosophilablack with ebony in fly optic lobes reveals putative cooperative tasks in vision that evade electroretinographic detection. Journal of Comparative Neurology, 2013; 521 (6): 1207 DOI: 10.1002/cne.23247

Cite This Page:

Ruhr-Universitaet-Bochum. "Blind flies without recycling: How Drosophila recovers the neurotransmitter histamine." ScienceDaily. ScienceDaily, 18 March 2013. <www.sciencedaily.com/releases/2013/03/130318105116.htm>.
Ruhr-Universitaet-Bochum. (2013, March 18). Blind flies without recycling: How Drosophila recovers the neurotransmitter histamine. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2013/03/130318105116.htm
Ruhr-Universitaet-Bochum. "Blind flies without recycling: How Drosophila recovers the neurotransmitter histamine." ScienceDaily. www.sciencedaily.com/releases/2013/03/130318105116.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) — In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Reuters - Light News Video Online (Dec. 19, 2014) — Millions of monarch butterflies begin to descend onto Mexico as part of their annual migration south. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) — The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) — A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. 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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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