Regulation Of Gravitropism In Arabidopsis By OsIAA9

Auxin regulates various aspects of plant growth and development. The Auxin/Indole-3-Acetic Acid(Aux/IAA) genes encode short-lived transcriptional repressors that are targeted by the ubiquitin proteasome system (UPS). In Arabidopsis, there are29genes encode Aux/IAA proteins. Aux/IAA proteins regulate auxin-mediated gene expression by interacting with members of the Auxin Response Factor (ARF) protein family. In rice (Oryza sativa), there are about30genes encode Aux/IAA proteins, however, the functions of the rice Aux/IAA proteins remain largely unknown.In this thesis, we describe the characterization of OsIAA9, an Aux/IAA gene in rice. RT-PCR analysis with RNA isolated from auxin treated and untreated rice seedlings showed that OsIAA9is an axuin responsive gene. Co-transfection assays in Arabidopsis protoplasts revealed that OsIAA9repressed the expression of the auxin response reporter gene DR5-GUS. Heterologously expression of OsIAA9in Arabidopsis led to reduced response to gravity, Taken together, these results suggest that OsIAA9is involved in the regulation of auxin signaling.