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May 9, 2008
Scientists at the
University of Amsterdam
have discovered how to keep one’s tomatoes from wilting – the
answer lies at the molecular level. The story of how the plant
beat the pathogen, and what it means for combating other plant
diseases, is published May 9th in the open-access journal
PLoS Pathogens.
Farmers and fellow agriculturalists are continuously battling
the ability of plant pathogens to co-evolve alongside their
host’s immune system. In agriculture, the most environmentally
friendly way to combat the evolutionary change in plant diseases
is to make use of the innate immune system of plants. Growers
can cross into targeted plant varieties certain polymorphic
resistance genes that occur in related plants, thereby naturally
boosting the plant’s immune system.
In this study, Dr. Martijn Rep and his team explored the
molecular basis of this previously established concept of
crossing in resistance genes. The authors considered the
interaction between a fungal pathogen, Fusarium oxysporum, and
the tomato plant in which the fungus causes Fusarium wilt
disease.
The group found that a small protein secreted by some strains of
the fungus causes it to overcome two of the tomato’s disease
resistance genes. However, a third resistance gene was shown to
specifically target this suppressor protein, rendering the plant
fully immune to any fungal strain that produces the protein.
Thus, with the right set of resistance genes, tomatoes can beat
the fungus despite the latter’s “molecular tricks.”
“This molecular analysis has revealed a hitherto unpredicted
strategy for durable disease control based on resistance gene
combinations,” say the authors.
PLoS Pathogens
publishes outstanding original articles that significantly
advance the understanding of pathogens and how they interact
with their host organisms. All works published in PLoS Pathogens
are open access. Everything is immediately available subject
only to the condition that the original authorship and source
are properly attributed. Copyright is retained by the authors.
The Public Library of Science uses the Creative Commons
Attribution License.
The Public Library of Science
(PLoS) is a non-profit organization of scientists and
physicians committed to making the world's scientific and
medical literature a freely available public resource.
Link to the articlehttp://www.plospathogens.org/doi/ppat.1000061
Suppression of
Plant Resistance Gene-Based Immunity by a Fungal
Effector
Petra M. Houterman, Ben J. C. Cornelissen, Martijn
Rep*
Plant
Pathology,
Swammerdam
Institute for Life Sciences,
University of
Amsterdam, Amsterdam, The Netherlands
Abstract
The innate immune system of plants consists of two
layers. The first layer, called basal resistance,
governs recognition of conserved microbial molecules
and fends off most attempted invasions. The second
layer is based on Resistance (R) genes that mediate
recognition of effectors, proteins secreted by
pathogens to suppress or evade basal resistance.
Here, we show that a plant-pathogenic fungus
secretes an effector that can both trigger and
suppress R gene-based immunity. This effector, Avr1,
is secreted by the xylem-invading fungus Fusarium
oxysporum f.sp. lycopersici (Fol) and triggers
disease resistance when the host plant, tomato,
carries a matching R gene (I or I-1). At the same
time, Avr1 suppresses the protective effect of two
other R genes, I-2 and I-3. Based on these
observations, we tentatively reconstruct the
evolutionary arms race that has taken place between
tomato R genes and effectors of Fol. This molecular
analysis has revealed a hitherto unpredicted
strategy for durable disease control based on
resistance gene combinations.
Author Summary
In agriculture, the most environmentally friendly
way to combat plant diseases is to make use of the
innate immune system of plants, for instance by
crossing into crop varieties polymorphic resistance
genes that occur in natural populations of the crop
plant or its close relatives. Plant pathogens,
however, have co-evolved with their host plants and
have developed ways to overcome the immune system.
To effectively make use of components of the plant
immune system, it is therefore important to
understand the co-evolution of plants and their
pathogens at the molecular level. For the
interaction between a fungal pathogen and tomato,
this paper presents a breakthrough in this respect.
A small protein secreted by some strains of the
fungus Fusarium oxysporum was found to suppress the
activity of two disease resistance genes of tomato.
However, a third resistance gene specifically
targets this suppressor protein and renders the
plant fully resistant against fungal strains that
produce it. With this insight, together with
knowledge of the genetic variation in the pathogen
population, a combination of resistance genes is
suggested that is expected to confer durable
resistance in tomato against Fusarium wilt disease. |
Full article:
http://www.plospathogens.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.ppat.1000061
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