In order to identify genes involved in auxin action we have isolated a number of mutants of Arabidopsis thaliana which are resistant co exogenous application of either indole-3-acetic acid or 2, 4-dichlorophenoxyacecic acid. One of the genes identified in chis way is the Axr1 gene. Recessive mutations in this gene confer resistance co auxin as well as a number of morphological defects. In this report we describe the isolation of at least two new axr1 alleles. In addition, we show that the axr1 mutation affects gravitropic growth of the root, auxin-induced ethylene biosynthesis and growth in tissue culture. Our results indicate chat the axr1 mutation is expressed in most tissues of the plant
