Halle plant geneticists achieve major advance in the eradication of pepper leaf blistering
Researchers at Martin Luther University contribute two articles to today’s edition of Science
Plant geneticists from Martin Luther University, Halle-Wittenberg (MLU) have contributed two articles to the current edition of the prestigious scientific journal Science, which appears today. Prof. Dr. Ulla Bonas, Dr. Thomas Lahaye and their colleagues have discovered how a pathogen specific to tomato and pepper plants actually works - and what mechanisms plants use to defeat this pathogen. Their findings may well have very important implications for agriculture. Scientists carrying out research into other plant diseases will probably also benefit from their work.
Publishing an article in Science, one of the most prestigious scientific journals in the world, is regarded as a real feather in one`s cap. As for being able to contribute two articles to the same edition, "That`s a real coup," says Prof. Dr. Ulla Bonas with pride. But the research success which underlies it is also a ‘coup`. The star of both articles is a protein called AvrBs3. "The gene which codes for this protein was isolated some twenty years ago; I worked on it during my postgraduate years," reports the researcher from Halle. "Afterwards, we tried to discover how it worked, piece by piece."
Bacteria which infect plants inject a cocktail of bacterial proteins directly into the plant cells by means of a needle-like structure. This cocktail, which is difficult to digest, causes affected plants to age more rapidly and bear fewer fruits. "AvrBs3 is a protein in this cocktail which is harmful to pepper and tomato plants. This component causes characteristic blistering to the leaves of pepper plants," explains Ulla Bonas. Bacterial pathogens are of little significance in this climatic zone, because they are not resistant to frost. "But in regions with warm, humid climates, such as Florida and Israel, the pathogen can be responsible for immense losses." [TL1] Unlike fungi, which can cause significant damage to plants at these latitudes, bacteria are easier for scientists to investigate.
Ulla Bonas and her colleagues at the Institute of Biology of Martin Luther University, have now discovered how the AvrBs3 protein works. "It penetrates directly to the nucleus of the plant cell, and, as a bacterial protein, displays the characteristics of a protein from a higher organism. Because of its structure, the bacterial protein is able to alter the gene regulation of its plant host. It operates in the cell nucleus, the distribution centre of the plant cell, and exploits the machinery of the host plant to its own advantage." This reprogramming causes a surge in the production of proteins, which are normally manufactured on a much smaller scale. "It is as if one accelerated production of a particular component in a factory. We have now been able to observe this acceleration," explains the principal author of the relevant article in Science.
Most bacterial proteins which manipulate their host attack at protein level. "But this bacterial protein activates genetic switches present in the nucleus, in other words it operates at DNA level, the level of genetic material. That is what is really new and so exciting about the findings," adds Dr. Thomas Lahaye. He is the principal author of the second article, which discusses plants which are resistant to the protein in question. "We were able to demonstrate that the plant then uses exactly the same mechanism as in the non-resistant plant. The bacterial protein switches on a gene which triggers local cell death. You might say that the cells which die alongside the pathogen sacrifice themselves. This puts a stop to bacterial reproduction." In all hitherto known resistance mechanisms of plants, plant proteins enable the pathogen to be identified. "In our case, the pathogen is recognised through its DNA. The protein which triggers cells death does not exist at the outset; it must first be manufactured. It is manufactured, and it has a completely new structure - that is what is new and ground-breaking about our results."
The plant geneticists from Halle have been conducting pure research, but are optimistic about the value of their latest findings in the real world. "One must first understand the mechanisms before practical applications are possible," explains Thomas Lahaye. "In the long term, our findings are very important for agriculture, and a number of companies are already interested in what we`ve been doing. In addition, many colleagues will be able to build on our work, for instance those who specialise in rice." Many bacteria are enormously destructive in rice fields throughout the world, and contain proteins which are very similar to AvrBs3. "What we have discovered is not specific to one pathogen family. The fact that we suspect the mechanism has broader validity is what makes it so exciting and important."
In the course of their research, the MLU scientists analysed some 4,500 pepper plants over the years. They have their own hot-house at the university`s biology centre on the Weinberg campus in Halle. The researchers have also used the greenhouse belonging to Halle`s BioCentre. Their work was funded by the German Research Foundation (DFG) within the context of Collaborative Research Centre 648 (‘Molecular Mechanisms of Information Processing in Plants`), whose spokeswoman is Prof. Dr. Ulla Bonas, and in response to an individual application submitted to the DFG by Dr. Lahaye. The MLU also has an Excellence Network entitled ‘Structures and Mechanisms of Biological Information Processing`, which was established as part of the offensive, ‘Networks of Scientific Excellence in Saxony-Anhalt`; this in turn owes its existence to the Ministry of Education and Cultural Affairs.
October 25th, 2007
Additional information on the internet:
http://www.sfb648.uni-halle.de (SFB 648)
http://www.sciencemag.org (Science magazine)
Contacts:
Prof. Dr. Ulla Bonas
Tel.: 0049-345-5526301 or 5526290
ulla.bonas@genetik.uni-halle.de
Dr. Thomas Lahaye
Tel.: 0049-345-5526345
thomas.lahaye@genetik.uni-halle.de