Abstract
Aux/IAA proteins repress activities of auxin response factors (ARF) by forming Aux/IAA-ARF heterodimers. Gain-of-function mutants in seven Aux/IAA genes show some overlapping phenotypes, but they are still distinct from each other, indicating functional differentiation in Aux/IAA genes. Because yeast two-hybrid assay shows promiscuous Aux/IAA-ARF interactions, it may be the specific patterns of gene expression that determine distinct phenotype of each mutant. In an attempt to check this possibility, we compared phenotypes of transgenic Arabidopsis plants which express the msg2/iaa19 or axr2/iaa7 cDNA under the control of IAA19 or 7 promoters. We first confirmed that both msg2/iaa19 and axr2/iaa7 transgenes reproduced their mutant phenotypes when they expressed under the control of their own promoters. However, they had no effects on morphology, when their promoters were swapped each other. These results suggest that function of the mutant IAA genes depends on distinct characteristics of their products.
