Research Area C

Responses of plant cells & tissues to natural & modified nucleotide-based immunostimulatory chemicals.

 

Project 6: Discovery and characterization of TIR-generated infochemicals in dicots and monocots; unraveling clade and lineage-specific principles of TIR-protein immunity (Prof. Dr. Jane Parker).

We will investigate immune responses of A. thaliana and barley (Hordeum vulgare) cells and tissues to natural nucleotide-based immunostimulatory chemicals. A set of TIR- generated non-cyclic phospho-ribosylated nucleotide immunostimulatory molecules (pRib- ADP/pRib-AMP, ADPr-ATP and di-ADPR) were discovered and their biochemical modes-of-action to directly activate A. thaliana EDS1-SAG101 and EDS1-PAD4 complexes, respectively leading to host cell death and basal immunity, was elucidated ((Huang et al., Science 2022; Jia et al., Science 2022). In further studies, plant TIR-domain proteins were classified into groups with distinctive TIR-
domain architectures and fusions with other domains (Johanndrees et al., Plant Phys 2023). Some of these TIR-groups are broadly conserved across dicot and monocot plant species and are predicted (based on mutational analysis) to produce immunostimulatory nucleotide chemicals. A small class of TIR-only proteins and a TIR-NB-tetratricopeptide repeat (TNP) protein are of particular interest because they induce, respectively, EDS1-dependent and EDS1-independent cell death in tobacco transient expression assays (Johanndrees et al., Plant Phys 2023). We will determine whether such TIRs add further immunostimulatory metabolites to the consortium for analysis, beyond those already identified. Furthermore we aim to elucidate the role of natural TIR-generated nucleotide-based infochemical activities in A.thaliana and barley immunity.

Project 7: Determination of the immunostimulatory properties of modified nucleotide-based infochemicals for potential applications to plants and testing in animal systems provided by the consortium (Prof. Dr. Stephanie Kath-Schorr).

We will test chemically synthesized natural and synthetic modified forms of plant non-cyclic nucleotide immunostimulatory molecules for actions on cells after liposome- or PEG-based delivery to protoplasts, and whole plant tissues after infiltration to the apoplast of leaves or uptake into the vascular system of roots. Hence, we aim to investigate the actions of chemically modified nucleotide infochemicals in plant cells and tissues.

Project 8:  Rational modification of infochemicals and mechanisms underlying choice between distinct nucleotide-based signaling pathways ( Prof. Dr. Kath-Schorr, Prof. Dr. Parker, Prof. Dr. Behrmann).

We strive to test new synthetic nucleotide analogs for immuno-stimulating activity in the in vivo assays developed in the other IPs. If modified nucleotide-based compounds do not display activity (measured by various defense outputs), we will test them in combined applications with microbial (PAMP) or damage (DAMP) elicitors on A. thaliana, barley and tobacco cells and tissues. This program will enable the characterization and tracking of modified nucleotide-based infochemicals in cells. It will additionally assess whether these molecules are sufficient to induce an immune response or require additional stress signals. Once a small molecule’s immunostimulatory activity has been established for a natural or chemically altered nucleotide-based compound, its capacity to induce tissues-wide responses leading to defense potentiation and pathogen resistance will examined in wild-type and mutant plants.