Project Details
Projekt
TERRAPHOS - Evolution of Phosphate Scouting during Plant Terrestrialization
Applicants
Professor Dr. Steffen Abel; Dr. Christin Naumann
Subject Area
Plant Cell and Developmental Biology
Term
since 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 528056313
Phosphorus is a biocritical element for all forms of life, but of minute abundance in the Earth’s crust. Globally, apatite minerals of volcanic rock are the only significant source of inorganic phosphate (Pi), the assimilated form of the macronutrient. Chemical and microbial rock weathering sequesters Pi into insoluble co-precipitates with metal cations, and by strong adsorption onto abundant metal oxides and oxyhydroxides into recalcitrant mineral (foremost FeIII und Al) phases. Thus, in rocky nascent soils, prospecting the essential but immobile nutrient posed a major challenge to the first emerging land plants (embryophytes) with only simple, rhizoid-based systems for water and nutrient absorption. Rhizomatous axes of the earliest embryophytes gave rise to the root systems of tracheophytes, including the capacity of growing root tips to monitor Fe-dependent Pi availability in the growth substrate (local Pi sensing). We recently showed that Arabidopsis LOW PHOSPHATE ROOT 1 (LPR1) plays a dominant role in local Pi sensing and typifies a novel, bacterial-type cohort of Fe-oxidizing multicopper oxidases (MCOs), which are ubiquitous in the land plants and encoded by small orthogroups (1-5 genes). Intriguingly, the progenitor of the streptophytes (charophyte freshwater algae plus land plants) acquired LPR1-type MCO ferroxidase from soil-dwelling bacteria via horizontal gene transfer (HGT). At least two additional genes, coding for an ABC transporter complex involved in Fe-dependent root Pi sensing, were transferred during the same HGT episode. Arabidopsis LPR1 also affects root hair development, which is controlled by evolutionary conserved processes shared with rhizoid formation. Thus, LPR1-type MCOs offer an excellent framework for dissecting the impact of HGT on the evolution of land plants and their adaptations to dramatically altered geochemical conditions. The first goal of our project will test the predicted biochemical activity of LPR1-like MCOs as specific ferroxidases. We will express, purify, and determine kinetic parameters of recombinant LPR1-type MCOs from select seedless tracheophytes, bryophytes, streptophyte algae, and soil-dwelling bacteria, which cover the evolutionary range relevant to plant terrestrialization. To probe a possibly conserved function in local Pi sensing, we will conduct complementation analyses with select LPR1-type MCO genes in Arabidopsis lpr1 knockout lines. A second goal will test the proposition that the acquisition of LPR1-type MCO ferroxidase activity facilitated the evolution of Fe-dependent Pi sensing during plant terrestrialization. We will use the established Marchantia bryophyte model system to characterize Pi deficiency responses and to analyze by reverse genetics the function of presumed key players in Marchantia such as LPR1-type MCOs for external Pi sensing.
DFG Programme
Priority Programmes
