Figure 7.

Proposed model for PXA1 function in Arabidopsis. Based on its homology to human and yeast proteins, PXA1 is predicted to be a transporter localized in the peroxisomal membrane. Because of the mutant phenotype, PXA1 is likely to import fatty acyl (FA)-CoA esters, IBA-CoA, and 2,4-DB-CoA into the peroxisome, where they are catabolized to succinate, IAA, and 2,4-D, respectively. 2,4-DB-resistant mutants defective in an acyl-CoA oxidase (acx3, Eastmond et al., 2000), a multifunctional protein (aim1, Richmond and Bleecker, 1999), and a thiolase (ped1, Hayashi et al., 1998) also are IBA resistant (Zolman et al., 2000; B. Zolman and B. Bartel, unpublished data), suggesting that these isozymes act directly in IBA and 2,4-DB β-oxidation. See text for details.