Calcium-promoted interaction between EHB1 and IRT1 inhibits iron acquisition (Plant Phys)

Iron uptake is tightly controlled so that the plant takes up not too much but not too little. Khan et al. used a yeast two-hybrid screen to search for proteins that interact with the iron transporter IRT1. They identified a protein previously shown to be involved in the hypocotyl bending response, EHB1 (ENHANCED BENDING1), which has a calcium and lipid binding domain. Their results suggest that EHB1 and IRT1 interact in a calcium-dependent manner at the plasma membrane. The authors also performed molecular dynamics simulations of EHB1 binding to the membrane, which suggest that it interacts via the calcium-binding site. Under low iron conditions, loss-of-function ehb1 mutants appear less iron-deficient, suggesting that EHB1 is a negative regulator of iron uptake. The authors demonstrate that through its binding, EHB1 directly inhibits IRT1 function. (Summary by Mary Williams) Plant Physiol. 10.1104/pp.19.00163