Evolution of Molecular Plant Microbe Interactions
Plants and their pathogens are constantly adapting to each other. Plants have several ways to fend off pathogens. For example: they have wax on their leaves or contain chemicals that pathogens don't like. Plants can also use so-called Resistance genes (R-genes). These R-genes detect small molecules from the pathogens and trigger defence responses. On their genomes, plants have huge amounts of R-genes. They appear to be very fast evolving in many species, so each species is optimally protected against the pathogens it could encounter where it grows.
Plant pathogens, however, are not just hanging around doing nothing. Pathogens secrete small effector molecules. These molecules can prevent or block defence responses. Unfortunately for the pathogens, the plants in their turn are able to also detect or circumvent these effectors. So pathogens also experience constant evolutionary pressure on their attack mechanisms. This means that, in plants and pathogens, R-genes and effectors are thought to constantly evolve and adapt to each other. This is the arms race of plant-pathogen interactions.
A lot of studies have shown the molecular interaction between R-genes and pathogen molecules. Also, more and more is known about the way effectors work. In fact whole journals and societies are dedicated to these Molecular Plant-Microbe Interactions (MPMI). We know that these adaptations of effectors and R-genes happen in the long term. Plant species that grow in different places and encounter different pathogens have different R-genes and also the effectors of different (even closely related pathogen-species) appear to be different.
On the other side, evolutionary biologists (Evo) have created nice models of how genes should behave in populations if they have positive and negative effects. They also have designed methods to evaluate evolutionary changes in populations of various species.
What we now hope to do in the following years is to bring these fields closer together. We want to really understand what is going on in terms of evolution in plant and pathogen populations in the wild, to understand the complexity of molecular plant-microbe interactions. It is time to do EvoMPMI.
To do this, we need a model species that is both relevant, related to a well studied crop and also has a known evolutionary history. The wild tomato species Solanum Chilense meets all these criteria. We have shown that within the species, different populations show different responses to a range of pathogens. Simultaneously, we have developed NGS based pipelines that can help identify genetic polymorphisms between and within populations. Next we want to bring these things together and study the differences on a molecular level between plants and pathogen populations to identify which factors are changing over space and or time.
Understanding these factors might help plant breeders to design more durable strategies for resistance breeding and could help understand how pathogens that seem harmless in one year can cause epidemics in the other.