Molecular mechanism regulating MAPKs activation within resistance complexes

A major challenge for the coming years is to provide food for an increasing number of people. Global demand for natural resources and the decreasing area of arable land are driving up the costs of energy and food. Therefore, it is of great importance to increase current crop production in a sustainable manner. Minimizing agricultural losses from pathogens will substantially increase crop yield and decrease the cost of food production.
During the last decades the field of plant-microbe interactions has made impressive progress revealing the basic architecture of the immune system. We now know that through evolution, plants have developed resistance (R) genes encoding immune receptors that recognize pathogen-derived elicitor molecules to activate immunity. Currently our main strategy to combat diseases in field conditions is the deployment of resistance (R) genes in crops. This resistance is often rapidly overcome in agriculture by evolving pathogen populations. However, our understanding of R genes mediated plant immunity is still in its infancy, and many important questions remain open. There is very little known about host immune mechanisms beyond pathogen recognition by R proteins. Mitogen-activated protein kinases (MAPKs) are one group of enzymes activated by R proteins. In eukaryotes, MAPKs exist in cascades that are necessary for functional immunity. R proteins can initiate activation of MAPKs cascades but the molecular mechanisms controlling this activation are completely unknown. Understanding the molecular mechanisms bridging the gap between activated R proteins and downstream MAPKs will be a vital step into engineering plants with durable resistance.
In work leading to this proposal we identified MAPKs as part of an R protein complex in tomato. This is the first time that MAPKs have been shown to be part of a resistance complex and gives us a clear picture of a molecular mechanism bridging the gap between activated R proteins and downstream signaling in a crop plant. This proposal aims to use this tomato R protein complex as a model for the characterization of the molecular mechanisms regulating MAPKs activation within the resistance complexes. We will use this knowledge to investigate the existence of a similar mechanism in other R protein complexes initially in the model plant Arabidopsis thaliana and in future work in crop plants

Plants have evolved two strategies of pathogen perception, extracellular recognition of microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs) and intracellular recognition of effectors by plant resistance (R) proteins. Commonly, R proteins containing a central nucleotide-binding (NB) motif of the STAND class, and C-terminal leucine rich repeats (LRRs) and recognise specific effectors directly or indirectly. The conserved architecture of NB-LRR proteins suggests a common activation mechanism. NB-LRR proteins are often products of dominant resistance (R) genes, which are frequently deployed in agriculture for disease control.
Despite our advances in the identification of immune receptors an apparent gap exists between recognition and downstream functional immunity. Mitogen-activated protein kinases (MAPKs) are one group of enzymes with known roles in immunity. We know that recognition by immune receptors leads to MAPKs activation but the molecular mechanisms activating MAPKKKs are completely unknown. Understanding the molecular mechanisms bridging the gap between activated receptors and downstream MAPKs cascades will be a vital step into engineering plants with durable resistance.
In work building up to this proposal using the tomato NB-LRR/accessory protein complex Prf/Pto we identified 14-3-3 proteins and MAPKKKa as part of the Prf/Pto resistance complex. This is the first time that MAPKKKs are shown to be part of a resistance complex and reveals a specific molecular mechanism bridging the gap between activated NB-LRRs proteins and downstream signaling.
This proposal aims to use the Prf/Pto complex as a model for the characterization of the molecular mechanisms regulating MAPKKKs activation within the resistance complexes. Subsequently, we will use this knowledge to investigate the existence of a similar mechanism in other NB-LRR complexes and identify NB-LRRs/14-3-3s/MAPKKKs interacting partners that regulate immunity.

Academics and researchers: This study will provide a mechanistic understanding of how pathogen perception leads to functional immunity. Immune receptors, MAPKKKs and 14-3-3 proteins are conserved in eukaryotic organisms. NB-LRR proteins across kingdoms share a common architecture that appears to reflect a common activation mechanism. Knowledge acquired and techniques developed from this proposal will be of interest for plant and animal biologists.
Implementation: We will publish our findings in high impact journals (open access, where possible). We will present our findings at national and international meetings.

The UK and international science base: An apparent gap exists in our knowledge of how activation of immune receptors leads to MAPKKK phosphorylation and downstream cascades. Despite that, we are not aware of any group currently working toward bridging this gap. This work has the potential to make an important scientific breakthrough that will attract considerable international interest and strengthen the UK's scientific position.
Implementation: We have excellent relations with many labs studying plant-microbe interactions within the UK and we will share our data and encourage collaboration in order to achieve as much synergy as possible.

Agro-industry and plant-breeders: Significant investments by research-funding bodies and industry have been made the last decades to engineer plants resistant to pathogens by deployment of resistance (R) genes in crops. This resistance is often rapidly overcome in agriculture by evolving pathogen populations. Elucidating the molecular mechanisms bridging activated R proteins with the downstream cascades will enhance our understanding of plant immunity and will be a valuable tool for our efforts toward engineering future crop plants with durable resistance.
Implementation: During this project we will work with Warwick Ventures who handle all issues relating to IP generated within the University's research program and who have a budget for providing protection of IP, for example through patents or other means. Warwick has strong links with industry (e.g. Syngenta) and we can work with these partners to explore opportunities for exploiting these patents.

Postdoctoral researcher associate (PDRA): The project offers unique training opportunities in multiple disciplines. The PDRA will be encouraged to further develop their writing and communication skills. Furthermore, the PDRA will be supported to develop her/his future applications to become a principal investigator.
Implementation: The PDRA will be trained in a number of cutting edge technics described in this application. Warwick Systems Biology Centre will support the PDRA in developing her/his bioinformatics skills. Warwick Learning and Development Centre offers a wide range of courses including scientific writing and communications courses and the PDRA will be encourage to attend these courses. The PI has recently awarded the Royal Society Fellowship and he will use his experience to help the PDRA develop her/his applications for fellowships to become a principal investigator.

Public: The use of genetically modified plants is a topic of high interest among the public. Currently, the general public is against the use of transgenic plants. To increase public's acceptance of genetically modified plants it is important to anticipate potential future problem of transgenic crops before are released for commercial use to avoid further damaging the public's trust in plant scientists. The outcome of this proposal will add to our efforts to understand plant innate immunity, which will help us to extend the lifetime of existing resistance cultivars and will be a vital step into engineering future crop plants with durable resistance.
Implementation: Warwick University has excellent public relation team and the PI is committed to communicate his research through visits to local schools, local, national, and international media.