Indole-3-acetic acid (IAA), the natural auxin in plants, regulates many aspects of plant growth and development. Extensive analyses have elucidated the components of auxin biosynthesis, transport and signaling, but the physiological roles and molecular mechanisms of auxin degradation remain elusive. Wan’s group demonstrated that the DAO (Dioxygenase for Auxin Oxidation) gene, encoding a putative 2-oxoglutarate-dependent-Fe (II) dioxygenase, is essential for anther dehiscence, pollen fertility and seed initiation in rice. Rice mutant lines lacking a functional DAO display increased levels of free IAA in anthers and ovaries. Furthermore, exogenous application of IAA or overexpression of the auxin biosynthesis gene OsYUCCA1 phenocopies the dao mutants. It is shown that recombinant DAO converts the active IAA into biologically-inactive2-oxoindole-3-acetic acid (OxIAA) in vitro. Collectively, these data support a key role of DAO in auxin catabolism and maintenance of auxin homeostasis central to plant reproductive development (See Figure). The dao mutant phenotype is similar to the hybrid sterility and this result will be a solid foundation for rice heterosis utilization.

The research was cooperated by scientists of ICS-CAAS, the National Key Laboratory for Crop Genetics and Germplasm Enhancement and Nanjing Agricultural University.

The results were published online on Developmental Cell:
http://www.sciencedirect.com/science/article/pii/S1534580713005133