Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Plant defenses prompt bacterial countermeasure in the form of ’island’ DNA excision

20.12.2005


Seeking to catch an arms-race maneuver in action, researchers have uncovered new evidence to explain how bacteria in the process of infecting a plant can shift molecular gears by excising specific genes from its genome to overcome the host plant’s specific defenses.



Throughout evolution – in the wild and in crops cultivated by humans – plants have developed systems for resisting the attack of microbial pathogens, while these microbes themselves have depended on their ability to alter molecular attack strategies in order to flourish. In the new work, researchers have essentially caught one step of this arms race in action, and they have shed light on the molecular mechanisms employed by a bacterial pathogen to survive in the face of its host plant’s defenses. The research is reported by John Mansfield and colleagues at Imperial College London, the University of the West of England, and the University of Bath.

Studying interactions between strains of the halo-bright pathogen and bean plants, the researchers found that the pathogenic bacteria essentially kicks out a section of its genome when it senses that its presence has been detected by the plant’s defense system. Excising this so-called "genomic island" eliminates production of the bacterial protein detected by the plant and allows a more stealthy – and successful – invasion.


The reason the strategy can be successful is that the plant has evolved to recognize the presence of only certain bacterial proteins as warnings of an infection. This means that the bacteria can, in principle, evade detection if it can shut down production of the offending protein or proteins. In their study, the authors identify within the halo-bright pathogen genome a special island of DNA that encodes one such offending protein. But this genomic island also encodes enzymes that, when switched on, snip the DNA on either side of the island, resulting in the excision of the entire island from the genome. The researchers found that this excision occurs in response to a so-called hypersensitive resistance reaction by the plant . The specific plant signals that are sensed by the pathogen to trigger the excision event remain to be identified.

If some bacterial proteins give away the presence of the pathogen to the plant, why are they and their surrounding genomic islands maintained by the bacteria at all? There are many genes included in the genomic island that is excised by the halo-bright strains studied here, and these other genes may well encode proteins that allow the pathogen to survive optimally in the light-intensive regions of eastern and southern Africa where these strains are found. Remarkably, bacteria that have excised the genomic island do not appear compromised in their ability to grow and cause disease within the host bean plant.

These findings offer a molecular explanation for how exposure to plant resistance mechanisms can directly drive the evolution of new virulent forms of a bacterial pathogen.

Heidi Hardman | EurekAlert!
Further information:
http://www.current-biology.com

More articles from Life Sciences:

nachricht Meadows beat out shrubs when it comes to storing carbon
23.11.2017 | Norwegian University of Science and Technology

nachricht Migrating Cells: Folds in the cell membrane supply material for necessary blebs
23.11.2017 | Westfälische Wilhelms-Universität Münster

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: New proton record: Researchers measure magnetic moment with greatest possible precision

High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons

The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...

Im Focus: Frictional Heat Powers Hydrothermal Activity on Enceladus

Computer simulation shows how the icy moon heats water in a porous rock core

Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...

Im Focus: Nanoparticles help with malaria diagnosis – new rapid test in development

The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.

Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Lightning, with a chance of antimatter

24.11.2017 | Earth Sciences

A huge hydrogen generator at the Earth's core-mantle boundary

24.11.2017 | Earth Sciences

Scientists find why CP El Niño is harder to predict than EP El Niño

24.11.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>