Ghent, Belgium
1 April 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.
Choosing between growth or defense
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 chain reaction in motion, starting with the degradation of the so-called JAZ proteins. This in turn frees up another protein (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 defense mechanism, 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.
BACKGROUND
Relevant scientific publication
This research appears in the authoritative journal Nature (Pauwels, Fernández Barbero, Geerinck et al., NINJA connects the co-repressor TOPLESS to jasmonate signalling).
Funding
This research has been funded by: VIB, Ghent University, FWO, IWT, NIH, the Spanish Ministry of Science and Technology and the Community of Madrid.
VIB is a non-profit research institute in the life sciences in Flanders, Belgium. About 1200 scientists conduct strategic basic research on the molecular mechanisms that are responsible for the functioning of the human body, plants, and micro-organisms. Through a partnership with four Flemish universities – Ghent University, the Katholieke Universitiet Leuven, the University of Antwerp, and the Vrije Universiteit Brussel − and a solid funding program, VIB unites the forces of 72 research groups in a single institute. Through its technology transfer activities, VIB strives to convert the research results into products for the benefit of consumers and patients. VIB develops and disseminates a wide range of scientifically substantiated information about all aspects of biotechnology. For more information, please visit www.vib.be.
After more than twenty years of uninterrupted growth, Ghent University is now one of the most important institutions of higher education and research in the Low Countries. Ghent University yearly attracts over 30,000 students, with a foreign student population of over 2,200 EU and non-EU citizens. Ghent University offers a broad range of study programs in all academic and scientific fields. With a view to cooperation in research and community service, numerous research groups, centers and institutes have been founded over the years. For more information: www.UGent.be
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