Persulfide metabolism in signaling and plant pathogen response

• Applicant: Professorin Dr. Tatjana Hildebrandt
• Subject Area: Plant Physiology
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 426095238

Hydrogen sulfide has been established as a gaseous signaling molecule taking part in the regulation of several physiological processes such as vasorelaxation in animals as well as stomatal movement and autophagy in plants. Recently it became apparent that the actual signal might be the more reactive persulfide, which can be attached to proteins in the course of a post-translational modification called sulfhydration. However, the physiological function of this regulatory process has not been established yet and the biochemical mechanisms of protein sulfhydration and de-sulfhydration are largely unknown. Defects in the persulfide oxidizing enzyme, the sulfur dioxygenase ETHE1, lead to the fatal metabolic disease ethylmalonic encephalopathy in humans. Our previous results indicate that in plants ETHE1 is part of a mitochondrial cysteine degradation pathway. Knockdown of the sulfur dioxygenase in Arabidopsis leads to a disturbance in amino acid homeostasis, premature leaf senescence, and constitutive activation of pathogen defense reactions. Since persulfides accumulate in the mutant plants, these phenotypic effects are most likely mediated by a dysregulation of persulfide signaling. Increased pathogen resistance was also found in des1-1, a muntant line defective in cytosolic cysteine degradation. Thus, we will quantify changes in metabolite and protein levels in ETHE1 knockdown plants as well as in des1-1 plants compared to the wild type in order to identify essential steps during persulfide signaling including the signal molecules involved and their targets. The sulfhydration profile will be analyzed using a recently developed mass spectrometry based method, which identifies all sulfhydrated proteins in a sample and in addition quantifies the proportion of modification for each protein to estimate their level of regulation. Mutant lines defective in key steps of pathogen defense pathways as well as double mutants will help to identify the regulatory mechanism leading to the activation of an immune reaction in the ETHE1 knockdown plants. Finally, we will integrate all new information to present a revised model of signaling events during plant pathogen response. The results of this project will increase basic knowledge about persulfide signaling and sulfhydration as a post-translational protein modification. We also seek to understand how plants regulate cysteine degradation to maintain a balance between effective disease resistance and metabolic homeostasis, which is crucial for survival and plant productivity. Detailed knowledge about signaling events leading to the different defense reactions is a prerequisite for engineering pathogen resistant crops without major harvest deficits. Since the sulfur dioxygenase ETHE1 is also present in animals certain aspects of sulfur catabolism might be conserved across kingdoms and thus relevant for understanding and treating human diseases.

• DFG Programme: Research Grants