Evolutionary alterations in gene expression and enzymatic activities of gibberellin 3-oxidase 1 in Oryza

Proper anther and pollen development are important for plant reproduction. The plant hormone gibberellin is important for anther development in rice, but its gametophytic functions remain largely unknown. Here, we report the functional and evolutionary analyses of rice gibberellin 3-oxidase 1 (OsGA3ox1), a gibberellin synthetic enzyme specifically expressed in the late developmental stages of anthers. Enzymatic and X-ray crystallography analyses reveal that OsGA3ox1 has a higher GA₇ synthesis ratio than OsGA3ox2. In addition, we generate an osga3ox1 knockout mutant by genome editing and demonstrate the bioactive gibberellic acid synthesis by the OsGA3ox1 action during starch accumulation in pollen via invertase regulation. Furthermore, we analyze the evolution of Oryza GA3ox1s and reveal that their enzyme activity and gene expression have evolved in a way that is characteristic of the Oryza genus and contribute to their male reproduction ability.