OsGA3ox genes regulate rice fertility and plant height by synthesizing diverse active GA.

Gibberellin (GA) is an important hormone, which is involved in regulating various growth and development. GA biosynthesis pathway and synthetase have been basically clarified. Gibberellin 3β hydroxylase (GA3ox) is the key enzyme for the synthesis of various active GA. There are two GA3ox genes ( OsGA3ox1 and OsGA3ox2 ) in rice, and their physiological functions have been preliminarily studied. However, it is not clear how they work together to synthesize active GA to regulate rice development. In this study, the knockout mutants ga3ox1 and ga3ox2 were obtained by CRISPR/Cas9 technology. The pollen fertility of ga3ox1 decreased significantly, while the plant height of ga3ox2 decreased significantly. It shows that OsGA3ox1 is necessary for normal pollen development, while OsGA3ox2 is necessary for stem and leaf elongation. Tissue expression analysis showed that OsGA3ox1 was mainly expressed in unopened flowers, while OsGA3ox 2 was mainly expressed in unexpanded leaves. The GA in different tissues of wild type (WT), and two ga3ox mutants were detected. It was found that pollen fertility is most closely related to the content of GA ₇ , and plant height is most closely related to the content of GA ₁ . It was found that OsGA3ox1 catalyzes GA ₉ to GA ₇ in flowers, which is closely related to pollen fertility; OsGA3ox2 catalyzes the GA ₂₀ to GA ₁ in unexpanded leaves, thereby regulating plant height; OsGA3ox1 catalyzes the GA ₁₉ to GA ₂₀ in roots, regulating the generation of GA ₃ . OsGA3ox1 and OsGA3ox2 respond to developmental and environmental signals, and cooperate to synthesize endogenous GA in different tissues to regulate rice development. This study provides a reference for clarifying its role in GA biosynthesis pathway and further understanding the function of OsGA3ox .