We are studying the immune responses of Arabidopsis thaliana (a plant dicot model) and barley (Hordeum vulgare; a monocot model) cells and tissues to nucleotide-based immunostimulatory chemicals. A set of natural non-cyclic phospho-ribosylated nucleotide immunostimulatory second messengers (pRib-ADP/pRib-AMP, ADPr-ATP and di-ADPR) were discovered as enzymatic products of pathogen-induced Toll-Interleukin-1 Receptor (TIR)-domain proteins. The biochemical modes-of-action of these small molecules (SMs) as direct activators of A. thaliana EDS1-SAG101 and EDS1-PAD4 complexes, respectively controlling host cell death and basal immunity, was elucidated (Huang et al, 2022; Jia et al, 2022). In iHEAD, we are exploring different plant TIR-protein enzymes and the range of TIR products that accumulate in dicot and monocot backgrounds. For the analysis, in vitro and in vivo nucleotide-based infochemical profiling is being developed in collaboration with Christian Frezza and the iHEAD metabolomics platform. Together with the organic chemistry group of Stephanie Kath-Schorr at Uni. Köln, we are testing chemically synthesized natural and bioengineered SMs for immunostimulatory activities in vitro and in plant cells and tissues. We aim to track the localizations, actions and persistence of modified SM analogs inside plants to better understand their in vivo properties.

Literature

Huang S, Jia A, Song W, Hessler G, Meng Y et al. Identification and receptor mechanism of TIR-catalyzed small molecules in plant immunity. Science 377, 487 (2022).

Jia A, Huang S, Song W, Wang J, Meng Y et al. TIR-catalyzed ADP-ribosylation reactions produce signaling molecules for plant immunity. Science 377, 488 (2022).