Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Planting the seeds of defense

08.08.2012
Salk study finds stress triggers widespread epigenetic changes that aid in disease resistance

It was long thought that methylation, a crucial part of normal organism development, was a static modification of DNA that could not be altered by environmental conditions.


The Salk researchers infected two lines of plants with a bacteria to determine whether methylation, a type of epigenetic chemical modification to DNA, plays a role in a plant's response to stress. The leaf on the left, taken from a normal plant five days after infection, shows disease systems. The leaf on the right, taken from a mutant plant incapable of methylation, shows no signs of disease, suggesting that methylation functions in stress responses.

Credit: Image: Courtesy of Robert H. Dowen

New findings by researchers at the Salk Institute for Biological Studies, however, suggest that the DNA of organisms exposed to stress undergo changes in DNA methylation patterns that alter how genes are regulated.

The scientists found that exposure to a pathogenic bacteria caused widespread changes in a plant's epigenetic code, an extra layer of biochemical instructions in DNA that help control gene expression. The epigenetic changes were linked to the activity of genes responsible for coordinating a plant's response to stress, suggesting that the epigenome may help organisms develop resistance to pathogens and other environmental stressors.

"This means the epigenome may not just be a static set of instructions, but also a way of rewriting those instructions based on experience," says Joseph Ecker, a professor in Salk's Genomic Analysis Laboratory, who led the research team. "Our findings, combined with other researchers' findings, build the case that life experiences leave an imprint on our DNA."

In the study, published online June 25 in the Proceedings of the National Academy of Sciences, Ecker and his colleagues studied how DNA methylation regulates the immune system of the Arabidopsis thaliana plant. Methylation is a biochemical process that, among other things, suppresses the expression of "jumping genes" called transposons that have been incorporated into the genome over time. Using genome-wide sequencing technologies, the researchers found a wide range of methylation changes in the plant's response to a bacterial infection and performed a variety of analyses to determine how these methylation changes alter gene expression.

"From previous studies, we know that the expression of a few genes is coupled to methylation changes in response to stress," says first author Robert Dowen, who worked on the project at Salk with Ecker and is now with Massachusetts General Hospital in Boston. "Our findings, however, show that exposing a plant to stress triggers a multitude of methylation changes that help the plant defend against invading pathogens."

Plants use a sophisticated series of defense mechanisms to restrict the growth of parasitic bacteria upon infection by stimulating various hormonal signals that trigger alterations in gene expression networks. The Salk findings and other recent studies suggest that these cellular defense responses engage the DNA methylation machinery to impart control over gene expression networks. Epigenetic changes in the genetic material, including changes in DNA methylation patterns and modifications to histones (proteins which play a key role in gene regulation), can alter the expression of a gene without changing its DNA sequence.

In addition, molecules called small interfering RNAs (siRNAs) are intimately connected with DNA methylation, especially at the jumping genes, where these siRNAs direct the methylation process. Surprisingly, the researchers found that the levels of these siRNAs also change during infection at specific transposons and correspond to activation of these mobile DNA fragments. These findings illustrate the dynamic nature of the epigenome in response to stress.

The Salk findings may have broad implications for agriculture, including engineering the DNA methylation patterns of plants to generate pathogen-resistant crops and minimize pesticide exposure. These application technologies are of intense interest, as more than 30 to 40 percent of annual crops are lost to pathogens each year at a cost of some $500 billion.

A recent study published in Plant Physiology suggests that memory of environmental conditions may be passed transgenerationally, as plant defenses are primed in the progeny of plants whose parents have already been exposed to pathogens. "While this phenomenon is poorly understood, it is of wide interest and is being intensively studied in the field," says Dowen. "We think our findings may provide a framework for directly testing whether the methylation changes that we observed are passed to the progeny or whether a similar mechanism may be occurring in human cells."

Other researchers on the study were Mattia Pelizzola, Robert J. Schmitz, Ryan Lister, and Joseph R. Nery, from the Salk Institute; and Jill M. Dowen and Jack E. Dixon of the University of California at San Diego.

The work was supported by the National Institutes of Health (AI060662), the Catharina Foundation, the California Institute for Regenerative Medicine, the Mary K. Chapman Foundation, the Howard Hughes Medical Institute and the Gordon and Betty Moore Foundation.

Andy Hoang | EurekAlert!
Further information:
http://www.salk.edu

More articles from Life Sciences:

nachricht Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg

nachricht Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>