A novel immunological approach establishes that the auxin-binding protein, Nt-abp1, is an element involved in auxin signaling at the plasma membrane.
Interactions of a collection of monoclonal antibodies (mAbs) to the recombinant Nicotiana tabacum auxin-binding protein 1 (Nt-abp1) were extensively characterized using surface plasmon resonance. Dynamic interaction studies using combinations of Nt-abp1, synthetic peptides corresponding to conserved sequences within auxin-binding proteins, and the mAbs have shown that a number of the mAbs recognized discontinuous epitopes revealing the junction of distinct domains in the folded protein. In particular, the two putative auxin binding domains and the C terminus of the protein were shown to interact with each other in the folded protein. Using the auxin-induced electrical response of tobacco protoplasts as a functional assay, all the mAbs exhibited either auxin antagonist or hormonomimetic properties. These effects, measured for the first time in homologous conditions, confirm that Nt-abp1 is present at the plasma membrane and is involved in the activation of the auxin-dependent electrical response of tobacco protoplasts. Based on our surface plasmon resonance data, we propose that the key event leading to the activation of this auxin electrical response consists of a conformational change in Nt-abp1.
Leblanc
N
N
Group of Auxin Perception and Transport, Institut des Sciences Végétales, CNRS, 91198 Gif sur Yvette, Cedex, France.
David
K
K
Grosclaude
J
J
Pradier
J M
JM
Barbier-Brygoo
H
H
Labiau
S
S
Perrot-Rechenmann
C
C
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology; D002462:Cell Membrane / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D010940:Plant Proteins; D010947:Plants, Toxic; D011487:Protein Conformation; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction; D014026:Nicotiana / Q000378:metabolism / Q000502:physiology
D000911:Antibodies, Monoclonal; D007210:Indoleacetic Acids; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083846:auxin-binding protein 1