Featured Research

from universities, journals, and other organizations

Conflict Between Plant And Animal Hormones In The Insect Gut?

Date:
September 18, 2009
Source:
Max Planck Institute for Chemical Ecology
Summary:
A reaction similar to the inactivation of prostaglandin hormones has now been discovered in the larval guts of two plant pest species. The insects bear an enzyme which structurally modifies and thereby inactivates OPDA, a highly active plant hormone. The results illustrate the close relationships and interactions of hormone activities in the animal and plant kingdoms.

This graphic shows plant oxylipins (cis-OPDA, iso-OPDA) and prostaglandins, hormones that play important roles in regulating metabolism and development in plants and humans. In plants as well as in animals the hormones derive from the oxidation of unsaturated fatty acids.
Credit: MPI Chemical Ecology

A reaction similar to the inactivation of prostaglandin hormones has now been discovered in the larval guts of two plant pest species. The insects bear an enzyme which structurally modifies and thereby inactivates OPDA, a highly active plant hormone. The results illustrate the close relationships and interactions of hormone activities in the animal and plant kingdom.

Cis-OPDA (12-oxophytodienoic acid) is a highly reactive plant hormone which simultaneously serves as a precursor molecule of the metabolic "master switch" jasmonic acid. Both signal herbivory in leaves and shoots of plants and activate the plants' defense reaction against caterpillars. Cis-OPDA, when reaching the hemolymph of the caterpillar, has a negative effect on the animal, leading to premature pupation and, apparently, an impaired immune system.

Paulina Dabrowska, one of the very first PhD students of the Jena International Max Planck Research School (IMPRS) who meanwhile earned her PhD, studied the whereabouts of plant hormones after they had been consumed by the caterpillars and had passed the insect gut. Are the hormones, which are known to severely influence development and metabolism of organisms even in the slightest dose, fully metabolized in the insect gut, just converted, or not influenced at all?

Studying the plant hormone cis-OPDA it became quickly evident that a conversion of the molecule must have taken place in the insect gut. The young chemist, originally from Poland, discovered that an enzyme must play a role in the chemical reaction observed: "First, we found that cis-OPDA was not present in the insect feces anymore. Instead of cis-OPDA, our mass spectrometers suggested iso-OPDA. However, iso-OPDA is only constituted by means of enzyme catalysis." Control experiments, solely performed in strong alkaline solutions as present in the insect gut (pH approx. 10), did not cause a cis-iso conversion. The test animals were Spodoptera littoralis (cotton leaf worm) and Helicoverpa armigera (cotton bollworm) larvae; both species are major cotton pests worldwide.

When isomerizing cis-OPDA to iso-OPDA, only one double bond in the molecule is relocated, drastically changing its spatial structure: An angulate molecule with a reactive double bond (cis-OPDA) becomes a planar molecule whose double bond can only react under forced conditions. A quite similar reaction has been previously described for prostaglandins, to be exact, the transformation of active prostaglandin A1 into inactive prostaglandin B1. OPDA and prostaglandins have a similar molecule structure and biosynthesis. Isomerization of these substances can be catalyzed by specific enzymes that, for instance, use glutathione as a substrate.

Therefore, Paulina Dabrowska and Dalial Freitak, another former IMPRS student, looked for corresponding genes in the genome of Helicoverpa armigera that encode such enzymes and found 16 different glutathione S-transferases (GSTs) in the insect gut. Only one of the enzymes catalyzes the cis-iso conversion of OPDA.

"This clearly demonstrates that of the 16 GSTs the cotton bollworm needs for many different metabolic pathways, this specific GST represents the evolutionary adaptation to its host plants," says Prof. Wilhelm Boland, in whose Department of Bioorganic Chemistry the studies have been carried out in cooperation with the Department of Entomology of Prof. David Heckel. The host spectrum of this insect pest is not limited to cotton, but includes many other plant species as well. The ability to inactivate cis-OPDA is especially found in host generalists (caterpillars with a broad food spectrum), but hardly ever in specialist insects.



Story Source:

The above story is based on materials provided by Max Planck Institute for Chemical Ecology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Paulina Dabrowska, Dalial Freitak, Heiko Vogel, David G. Heckel, Wilhelm Boland. The phytohormone precursor OPDA is isomerized in the insect gut by a single, specific glutathione transferase. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0906942106

Cite This Page:

Max Planck Institute for Chemical Ecology. "Conflict Between Plant And Animal Hormones In The Insect Gut?." ScienceDaily. ScienceDaily, 18 September 2009. <www.sciencedaily.com/releases/2009/09/090914142722.htm>.
Max Planck Institute for Chemical Ecology. (2009, September 18). Conflict Between Plant And Animal Hormones In The Insect Gut?. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2009/09/090914142722.htm
Max Planck Institute for Chemical Ecology. "Conflict Between Plant And Animal Hormones In The Insect Gut?." ScienceDaily. www.sciencedaily.com/releases/2009/09/090914142722.htm (accessed September 19, 2014).

Share This



More Plants & Animals News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

Raw: Elephant Undergoes Surgery in Tbilisi Zoo

AP (Sep. 18, 2014) Grand the elephant has successfully undergone surgery to remove a portion of infected tusk at Tbilisi Zoo in Georgia. British veterinary surgeons used an electric drill to extract the infected piece. (Sept. 18) Video provided by AP
Powered by NewsLook.com
Chimp Violence Study Renews Debate On Why They Kill

Chimp Violence Study Renews Debate On Why They Kill

Newsy (Sep. 17, 2014) The study weighs in on a debate over whether chimps are naturally violent or become that way due to human interference in the environment. Video provided by Newsy
Powered by NewsLook.com
Some Tobacco Farmers Thrive Amid Challenges

Some Tobacco Farmers Thrive Amid Challenges

AP (Sep. 16, 2014) The South's tobacco country is surviving, and even thriving in some cases, as demand overseas keeps growers in the fields of one of America's oldest cash crops. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

Scientists Given Rare Glimpse of 350-Kilo Colossal Squid

AFP (Sep. 16, 2014) Scientists say a female colossal squid weighing an estimated 350 kilograms (770 lbs) and thought to be only the second intact specimen ever found was carrying eggs when discovered in the Antarctic. Duration: 00:47 Video provided by AFP
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