Abstract
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.
Highlights
Proper anther and pollen development are important for plant reproduction
GAs are synthesized in a stepwise manner by multiple oxidases, and the conversion from direct precursors to bioactive GAs is mediated by GA 3-oxidases (GA3oxs)
We suggest that the evolution of the enzymatic function and gene expression of Oryza GA3ox[1] contribute to the reproductive advantage of Oryza plants
Summary
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. The analysis of starch and sucrose in anthers revealed that starch synthesis, in particular the conversion step of glucose from sucrose that is mainly regulated by invertases[22], was defective in osga3ox[1] mutant pollen (Fig. 2g, h).
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