The AUXIN BINDING PROTEIN 1 is required for differential auxin responses mediating root growth.
BACKGROUND
In plants, the phytohormone auxin is a crucial regulator sustaining growth and development. At the cellular level, auxin is interpreted differentially in a tissue- and dose-dependent manner. Mechanisms of auxin signalling are partially unknown and the contribution of the AUXIN BINDING PROTEIN 1 (ABP1) as an auxin receptor is still a matter of debate.


RESULTS
Here we took advantage of the present knowledge of the root biological system to demonstrate that ABP1 is required for auxin response. The use of conditional ABP1 defective plants reveals that the protein is essential for maintenance of the root meristem and acts at least on the D-type CYCLIN/RETINOBLASTOMA pathway to control entry into the cell cycle. ABP1 affects PLETHORA gradients and confers auxin sensitivity to root cells thus defining the competence of the cells to be maintained within the meristem or to elongate. ABP1 is also implicated in the regulation of gene expression in response to auxin.


CONCLUSIONS
Our data support that ABP1 is a key regulator for root growth and is required for auxin-mediated responses. Differential effects of ABP1 on various auxin responses support a model in which ABP1 is the major regulator for auxin action on the cell cycle and regulates auxin-mediated gene expression and cell elongation in addition to the already well known TIR1-mediated ubiquitination pathway.
Tromas
Alexandre
A
Institut des Sciences du Végétal, CNRS UPR2355, Université Paris Sud Orsay, Gif sur Yvette, France.
Braun
Nils
N
Muller
Philippe
P
Khodus
Tatyana
T
Paponov
Ivan A
IA
Palme
Klaus
K
Ljung
Karin
K
Lee
Ji-Young
JY
Benfey
Philip
P
Murray
James A H
JA
Scheres
Ben
B
Perrot-Rechenmann
Catherine
C
D017360:Arabidopsis / Q000235:genetics; D002453:Cell Cycle; D049108:Cell Enlargement; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D007700:Kinetics; D018519:Meristem / Q000502:physiology*; D008954:Models, Biological; D008957:Models, Genetic; D010937:Plant Growth Regulators / Q000378:metabolism / Q000502:physiology; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000502:physiology*; D018517:Plant Roots / Q000378:metabolism; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000502:physiology*
D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011956:Receptors, Cell Surface; C083846:auxin-binding protein 1