Abstract
Even after various physiological experiments, the molecular mechanism of auxin signaling in monocotyledonous plants remained unclear. To understand the function and mechanism of auxin signaling in rice, we focused on the IAA gene, a well-studied gene in Arabidopsis that serves as a negative regulator of auxin signaling. We found 24 IAA gene family members in the rice genome. OsIAA3 is one of the members whose expression is rapidly increased in response to auxin. We produced transgenic rice harboring mOsIAA3-GR, which can overproduce mutant OsIAA3 protein containing an amino acid change in domain II to cause a gain-of-function phenotype by treatment with dexamethasone. The transgenic rice was insensitive to auxin and gravitropic stimuli, and exhibited short leaf blades, reduced crown root formation, and abnormal cell arrangement in shoot-apical meristem. These results suggest that auxin is important for rice development and its signaling is mediated by the IAA genes in rice.
