Perception of long-chain N-acyl homoserine lactones in plants

• Applicant: Privatdozent Dr. Adam Schikora
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems ; Plant Breeding and Plant Pathology
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 282634159

The ability to monitor the surroundings is for plant of crucial importance. Microorganism-derived molecules, effector proteins and bacterial quorum sensing molecules (QSM) trigger specific reactions in plant organism. QS molecules are usually used for cell-to-cell communication within bacterial populations. In plants, QSMs induce multiple reactions, for example N-3-oxo-tetradecanoyl-L-homoserine lactone (oxo-C14-HSL) synthesized by Sinorhizobium meliloti primes Arabidopsis and barley for enhanced defense: augmented callose deposition, accumulation of phenolic compounds, and lignification of cell walls. Furthermore, increased levels of oxylipins and salicylic acid favor stomatal closure in response to pathogen. Although much is know on AHL perception in bacteria (LuxR family) and animals (PPAR receptors and the IQGAP1 G-protein), the knowledge on AHL recognition in plants is still very poor. Our goal in this project is to characterize AHL perception mechanism(s) in plants. We will use three independent strategies: i) Since the receptors of bacteria and animals are known, sequence similarities to plant proteins indicated a number of candidates with partial homologies. These proteins will be in focus of our candidate-based approach in which the respective mutants will be screened for the AHL effect; ii) In the pull-down/MS-MS and protein microarray approaches we will target proteins binding to modified AHLs. This characterization of AHL-binding complexes will allow an identification of proteins directly interacting with QS molecules. Here we will use newly synthesized molecules with a biotin tag or a photo-activated azide group; iii) The genetic variability within the Arabidopsis thaliana species bears a great potential. Analysis of different A. thaliana ecotypes revealed already a significant difference in the response to oxo-C14-HSL, indicating that some ecotypes are AHL-insensitive, whereas others respond to this molecule. Our third strategy will use chosen recombinant inbred lines (RILs) and allows the mapping of AHL-responsive locus (or loci) on the Arabidopsis genome. All strategies will be concluded with a verification step in which the identified candidates will be tested in independent techniques, including a surface plasmon resonance spectroscope and RNAi. We expect to uncover an array of AHL-interacting partners, which will serve as paradigm for the understanding of AHLs perception in plants. In addition to the ability of AHL perception, plants are able to influence the accumulation of AHLs in the medium. In collaboration with the group Klug and Hackenberg we will study the impact of plant signal(s) at the production of oxo-C14-HSL in S. meliloti. The characterization of the reciprocal impact of AHLs on plants and plants on AHL production will provide new insights into inter-kingdom communication and allow a fine-tuning for the future implementation of the gained knowledge in novel agricultural strategies.

• DFG Programme: Research Grants
• International Connection: USA
• Co-Investigators: Professor Dr. Wolfgang Maison, Ph.D.; Professorin Dr. Sorina Popescu