Featured Research

from universities, journals, and other organizations

How Pathogens Evolve To Escape Detection

Date:
July 19, 2007
Source:
Cornell University
Summary:
In the evolutionary battle in which plants are trying to beef up their defenses against pathogens, researchers have discovered a bacterium that infects tomatoes by injecting a special protein into the plant's cells and undermines the plant's defense system.

Tracy Rosebrock, a graduate student in plant pathology and lead author of a paper appearing in Nature, stands among wild varieties of tomato plants at the Boyce Thompson Intstitute on campus.
Credit: Robert Barker/Cornell University Photography

An arms race is under way in the plant world. It is an evolutionary battle in which plants are trying to beef up their defenses against the innovative strategies of pathogens. The latest example of this war is a bacterium (Pseudomonas syringae) that infects tomatoes by injecting a special protein into the plant's cells and undermines the plant's defense system.

"Plant breeders often find that five or six years after their release, resistant plant varieties become susceptible because pathogens can evolve very quickly to overcome plant defenses," said Gregory Martin, Cornell professor of plant pathology, a scientist at the Boyce Thompson Institute for Plant Research (BTI) on the Cornell campus and the senior author of the research paper, published in the July 19 issue of the journal Nature. "However, every now and then, breeders develop a plant variety that stays resistant for 20 years or more."

Understanding why some varieties have more durable disease resistance is important to the development of more sustainable agricultural practices, he said.

The study by Cornell and BTI scientists describes how a single bacterial protein, AvrPtoB, which is injected by P. syringae into plant cells through a kind of molecular syringe, can overcome the plant's resistance. Normally, the plant's defense system looks out for such pathogens and, if detected, mounts an immune response to stave off disease. As part of this surveillance system, tomatoes carry a protein in their cells called Fen that helps detect P. syringae and trigger an immune response.

But some strains of P. syringae have evolved the AvrPtoB protein that mimics a tomato enzyme known as an E3 ubiquitin ligase, which tags proteins to be destroyed. Once injected, AvrPtoB binds the Fen protein, and the plant's own system eliminates it, allowing the bacteria to avoid detection and cause disease.

"This paper explains how a pathogen can evolve to escape detection," said lead author Tracy Rosebrock, a graduate student in Cornell's Department of Plant Pathology and BTI. "The bacterium has one specific protein that it uses to turn off the plant's immunity."

The researchers found that the Fen gene is present in both cultivated tomatoes and many wild tomato species, leading them to believe that the gene is likely ancient in origin and that many members of the tomato family have used it to resist P. syringae infections over the years. Since the Fen protein still detects AvrPtoB-like proteins from some strains of P. syringae, prompting an effective immune response, the researchers believe new P. syringae strains have only recently evolved a version of AvrPtoB that includes an E3 ubiquitin ligase enzyme that interferes with the plant's surveillance.

"This paper provides molecular data that supports the evolutionary 'arms race' theory" that as pathogens develop new ways to spread and attack organisms, the organisms in turn create novel defenses, each in a continuous battle to outdo the other, said Rosebrock.

The research was funded by the National Institutes of Health, the National Science Foundation and the Triad Foundation, a private charitable trust.


Story Source:

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


Cite This Page:

Cornell University. "How Pathogens Evolve To Escape Detection." ScienceDaily. ScienceDaily, 19 July 2007. <www.sciencedaily.com/releases/2007/07/070718151055.htm>.
Cornell University. (2007, July 19). How Pathogens Evolve To Escape Detection. ScienceDaily. Retrieved September 18, 2014 from www.sciencedaily.com/releases/2007/07/070718151055.htm
Cornell University. "How Pathogens Evolve To Escape Detection." ScienceDaily. www.sciencedaily.com/releases/2007/07/070718151055.htm (accessed September 18, 2014).

Share This



More Plants & Animals News

Thursday, September 18, 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