Arabidopsis AUX1 Gene: A Permease-Like Regulator of Root Gravitropism

Malcolm J. Bennett, Alan Marchant, Haydn G. Green, Sean T. May, Sally P. Ward, Paul A. Millner, Amanda R. Walker, Burkhard Schulz & Kenneth A. Feldmann

The plant hormone auxin regulates various developmental processes including root formation, vascular development, and gravitropism. Mutations within the AUX1 gene confer an auxin-resistant root growth phenotype and abolish root gravitropic curvature. Polypeptide sequence similarity to amino acid permeases suggests that AUX1 mediates the transport of an amino acid-like signaling molecule. Indole-3-acetic acid, the major form of auxin in higher plants, is structurally similar to tryptophan and is a likely substrate for the AUX1 gene product. The cloned AUX1 gene can restore the auxin-responsiveness of transgenic aux1 roots. Spatially, AUX1 is expressed in root apical tissues that regulate root gravitropic curvature.

Science 273 (5277), 948-950

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