United Kingdom
December 4, 2008How a
bacterium overcomes a tomato plant's defences and causes
disease, by sneakily disabling the plant's intruder detection
systems, is revealed in new research out today in
Current Biology.
The new study focuses on a pathogen which causes bacterial speck
disease in tomato plants. This bacterial invasion causes black
lesions on leaves and fruit. Severe infection can cause
extensive and costly damage to tomato crops, and researchers
believe that understanding more about how this microbe works
could lead to new ways of tackling it, and other plant diseases,
without the need for pesticides.
Scientists have found that the pathogen is very effective at
attacking tomato plants because it deactivates and destroys
receptors which normally alert the plant to the presence of a
dangerous disease - in the same way that an intruder would
deactivate the burglar alarm before gaining entry to a house.
Professor John Mansfield from Imperial College London's
Department of Life Sciences, one of the authors of the paper,
says: "Once the receptors have been taken out, the plant's
defences are 'offline' and the bacterium is able to spread
rapidly, feeding on the plant without encountering any kind of
resistance."
Together with colleagues at the Max Planck Institute in Cologne
and Zurich-Basel Plant Science Centre, Professor Mansfield used
an experimental model plant called Arabidopsis, which is also
affected by the disease, to examine what happens at the
molecular level when bacterial speck infects a plant. The team
found that the pathogen injects a protein into the host cell,
which then deactivates and destroys, from the inside, receptors
on the cell's surface which are designed to alert the plant to
the presence of invading microbes.
Deactivating the receptors stalls the plant's defence mechanism
in its initial stages - ordinarily the cell surface receptors
would kickstart a chain reaction leading to the production of
antimicrobial compounds to fight and kill off the bacterial
invader.
Professor Mansfield says: "This area of research has a wider
significance beyond black speck disease in tomato, because the
microbes that cause plant diseases probably all employ similar
attacking strategies to suppress resistance in their hosts. The
more we understand about how the pathogens that cause disease
overcome the innate immunity to infection in crop plants, the
better our chances of developing approaches to disease control
that do not require the use of potentially harmful pesticides"
The research at Imperial was funded by the UK
Biotechnology and Biological
Sciences Research Council.
'The plant pattern
recognition receptor FLS2 is directed for degradation by the
bacterial ubiquitin ligase AvrPtoB'
Current Biology,
advance online publication, 4 December 2008.
Vera Gohre (1), Thomas Spallek (1), Heidrun Haweker (1),
Sophia Mersmann (1), Tobias Mentzel (2), Thomas Boller (2),
Marta de Torres (3,4) John W. Mansfield (3), Silke Robatzek
(1, 5).
(1)Max-Planck-Institute for Plant Breeding Research,
Carl-von-Linne-Weg 10, 50829 Cologne, Germany
(2)Zurich-Basel Plant Science Center, University Basel,
Hebelstrasse 1, 4056 Basel, Switzerland
(3)Imperial College London, Division of Biology, South
Kensington Campus, London SW7 2AZ, United Kingdom
(4)present address: School of Biosciences, Jeoffrey Pope
Building, Stoker Road, Exeter University, Exeter, EX4 4QD,
United Kingdom
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