Biologists discover an on/off button on plants' alarm system

April 1, 2010

Scientists connected to VIB and Ghent University have discovered how plants turn their defense mechanisms on and off. The system is apparently controlled by a key protein that the researchers have named "NINJA." The discovery offers possibilities for increasing the yield of therapeutic substances from plants. The authoritative scientific journal Nature is publishing the results today.

Plants respond to attacks by herbivores or pathogens by activating defense programs that drive off or even kill the attackers. These defense responses require a great deal of the plant's energy and reserves, which would otherwise be invested in growth and reproduction. So, it's very important to strictly control the activity of defense genes. Hormones, such as the jasmonates, are crucial in this process - and the plant produces these hormones when subjected to stress conditions.

The presence of the jasmonates sets a complex in motion, starting with the degradation of the so-called JAZ proteins. This in turn frees up another (MYC2), which is the signal for launching the genetic defense programs and stopping the plant's growth. The presence of the JAZ proteins keeps the defense mechanism 'turned off'. Until now, it has been unclear how the JAZ proteins are able to block the MYC2 protein's activity.

A trio of NINJA, JAZ and TPL

Thanks to the work of Laurens Pauwels and Jan Geerinck from the team of Alain Goossens (VIB/Ghent University), that problem has now been clarified. It turns out that a newly discovered protein called NINJA (Novel INteractor of JAZ) connects the JAZ proteins with still another protein called TPL. As long as these proteins appear as a trio, they bind to MYC2 and that protein remains inactive. The moment that the JAZ proteins disappear - as the consequence of stress and the subsequent production of the jasmonates - MYC2 springs into action, triggering the plant's defense mechanism. The researchers have worked with Spanish colleagues from the CSIC/University of Madrid and have used a proteomics-based technology developed by Geert De Jaeger (VIB/Ghent University) and Erwin Witters (VITO/University of Antwerp). This technology makes it possible to determine the composition and production of protein complexes in plants.

Link between growth and stress

It has previously been known that TPL suppresses the expression of genes controlled by the growth regulator auxin. The VIB researchers are now demonstrating that TPL proteins suppress other genes as well. In fact, they not only influence the regulation of a plant's growth but also other hormonally driven processes by interacting with proteins like NINJA.

This new insight reveals how stress- and growth-related signaling pathways use the same molecular mechanisms to regulate gene expression in plants and fills a major gap in our understanding of how plant hormones such as jasmonates regulate gene expression.

Pharmaceutical application

When plants turn on their , they start the production of secondary metabolites, a group of chemical substances exhibiting various therapeutic activities. Now that more is known about the regulation of these secondary metabolites, scientists can look for ways to step up their production.

Explore further: Internal clock, external light regulate plant growth

Related Stories

Internal clock, external light regulate plant growth

July 9, 2007

Most plants and animals show changes in activity over a 24-hour cycle. Now, for the first time, researchers have shown how a plant combines signals from its internal clock with those from the environment to show a daily rhythm ...

Researchers JAZ(zed) about plant resistance discovery

July 18, 2007

The mystery of how a major plant hormone works to defend plants against invaders has been revealed, thanks to collaborative research efforts by Michigan State University and Washington State University.

Scientists unveil mechanism for 'up and down' in plants

October 28, 2008

VIB researchers at Ghent University, Belgium, discovered how the transport of an important plant hormone is organized in a way that the plant knows in which direction its roots and leaves have to grow. They discovered how ...

Possible new hope for crops battling parasitic infection

January 16, 2009

Scientists from Ghent University and VIB (The Flemisch Institute for Biotechnology) have demonstrated how nematodes, also known as roundworms, manipulate the transport of the plant hormone auxin in order to force the plant ...

Understanding Natural Crop Defenses

February 28, 2009

Ever since insects developed a taste for vegetation, plants have faced the same dilemma: use limited resources to out-compete their neighbors for light to grow, or, invest directly in defense against hungry insects. Now, ...

Recommended for you

Secrets of a heat-loving microbe unlocked

September 4, 2015

Scientists studying how a heat-loving microbe transfers its DNA from one generation to the next say it could further our understanding of an extraordinary superbug.

Plants also suffer from stress

September 4, 2015

High salt in soil dramatically stresses plant biology and reduces the growth and yield of crops. Now researchers have found specific proteins that allow plants to grow better under salt stress, and may help breed future generations ...

Ancient walnut forests linked to languages, trade routes

September 4, 2015

If Persian walnut trees could talk, they might tell of the numerous traders who moved along the Silk Roads' thousands of miles over thousands of years, carrying among their valuable merchandise the seeds that would turn into ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.