Abstract
The transcriptional regulation system of auxin response indirectly controls the expression of auxin-responsive genes via auxin receptor TIR1/ABFs-dependent degradation of transcriptional repressor Aux/IAAs, which interact with auxin-responsive transcription factor ARFs. The functional analysis using dominant negative mutants demonstrated that Arabidopsis Aux/IAAs participate into the auxin-related organ formation system. In this study, we tried to clarify IAA8 function on organ formation system and identify IAA8-interacting ARFs. The estrogen-inducible IAA8 overexpressors showed reduced lateral root formation and abnormal gravitropism. In addition, yeast two hybrid assay revealed that IAA8 strongly interacts with ARF5, ARF7 and ARF19. Taken all, we suggested that phenotype changes caused by IAA8 overexpression would be derived from the functional suppression of ARFs interacting with IAA8. The analyzed data of dominant negative transgenic plants with IAA8 own promoter and IAA8 with the mutation on TIR1/ABFs recognition site and of protein-protein interaction between IAA8 and ARFs in plant cells using BiFC method are also reported.
