Figure 1.

IAA homeostasis pathways. A, Free IAA levels are maintained in plant cells by several mechanisms, including de novo biosynthesis and oxidative degradation. IAA-conjugate hydrolases (a) hydrolyze IAA conjugates to free IAA. IBA-response genes (b) are necessary to metabolize IBA to free IAA. MeIAA is converted to free IAA by MES17 (c). B, Genes involved in IAA input pathways are differentially expressed throughout development, which was revealed by the Arabidopsis eFP browser (Winter et al., 2007). Expression levels at three stages are shown here as an example.