Hyperpolarization of tobacco protoplasts is amongst the earliest auxin resp
onses described. It has been proposed that the auxin-binding protein, ABP1,
or a related protein could be involved in the first step of auxin percepti
on at the plasma membrane. Using for the first time homologous conditions f
or interaction between the protein Nt-ERabp1 or a synthetic peptide corresp
onding to the C-terminus and tobacco protoplasts, se have demonstrated that
both can induce the hyperpolarization response. The results show that Nt-E
Rabp1 or the C-terminal peptide alone activates the auxin pathway from the
outer face of the plasma membrane. (C) 1999 Federation of European Biochemi
cal Societies.