RESEARCH

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Impact of natural LPR1 proteoforms on Fe-dependent phosphate sensing

External inorganic phosphate (Pi) availability profoundly affects plant performance. When facing Pi limitation, often caused by antagonistic Fe:Pi interactions, plants enhance Pi recycling and acquisition by reprogramming metabolism and root development. In Arabidopsis (A. thaliana), cell wall-localized multicopper ferroxidase LOW PHOSPHATE ROOT 1 (LPR1) is a key determinant of Fe-dependent Pi sensing by root tips. LPR1 function is highly sensitive to substrate (Fe²⁺) availability, which is restricted by Pi co-occurrence. Constitutive LPR1 protein expression suggests LPR1 ferroxidase activity governs root tip growth in low Pi. LPR1-dependent Pi sensing is likely conserved in land plants because Arabidopsis LPR1 typifies an ancient ferroxidase family that evolved in Terra-bacteria. Land plant progenitors acquired bacterial LPR1-type ferroxidase, facilitating the evolution of Pi sensing and Pi acquisition. To date, analysis of LPR1 function in planta has been limited to null alleles and site-directed mutagenesis. Project C03 will study the impact of allelic LPR1 diversity on biochemical properties of LPR1 variants in relation to Fe-dependent Pi sensing.

We will focus on select LPR1 proteoforms to compare biochemical (enzymatic) properties, functional regulation in planta, protein-protein interaction by proximity labelling and cross-linking MS as well as consequences for Fe-dependent root Pi sensing in different growth (soil) conditions. In addition, we plan to solve crystal structure(s) of LPR1^Col-0, the prototypic bacterial LPR1-type ferroxidase, which will precisely rationalize functional LPR1 proteoform diversity and provide insight into LPR1-type ferroxidase evolution.

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