Interplay of chelating and reducing root exudates in plant iron acquisition

• Applicants: Dr. Günther Weber; Professor Dr. Nicolaus von Wirén
• Subject Area: Plant Cultivation, Plant Nutrition, Agricultural Technology
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 291474925

Due to the low iron (Fe) solubility in most soils, plants have evolved Fe acquisition strategies that are mainly based on the chelation and reduction of ferric Fe. While graminaceous plants release mugineic acid-type siderophores from their roots for ferric Fe chelation, non-graminaceous plants rely primarily on the reduction of ferric Fe which is compromised at high pH. Recently, a new class of coumarin-type siderophores has been identified in root exudates that mediate ferric Fe chelation, however, due to their high chemical versatility their mode of action in the rhizosphere is still unclear. Therefore, the present project aims at i) identifying new exudate compounds with novel or specific Fe-related functions, in particular regarding the chelation and/or reduction of Fe(III) and to characterize modifications and chemical interactions of these compounds on their way from the release by root cells through the root apoplast into the rhizosphere soil and back; ii) examining synergisms among individual root exudates involved in Fe mobilization by from Fe-bearing phases in the soil; iii) identifying and quantifying the contribution and interplay of chemical and biological processes involved in Fe acquisition via plant-exuded reductants and iron ligands in the rhizosphere. To address a set of 8 defined hypotheses, two German and two Austrian labs from molecular plant nutrition, analytical chemistry, rhizosphere ecology and biogeochemistry will collect root exudates from hydroponic and rhizosphere systems, conduct metal-chelate speciation by advanced mass spectrometry-coupled techniques, assess Fe chelation and redox chemistry of root exudates from wild-type and mutant plants and employ thermodynamic and kinetic modelling approaches. This proposal promises to chemically identify key players in root exudates and to describe their mode of action as chelators, reductants or redox shuttles for an improved Fe nutrition in plants.

• DFG Programme: Research Grants
• International Connection: Austria
• Cooperation Partners: Professor Dr. Stephan Krämer; Privatdozent Dr. Markus Puschenreiter