Rice isoflavone reductase‐like protein is associated with root development and ROS stress resistance

Abstract

Isoflavone phytoalexins and isoflavone reductase gene in the rice has not been identified and characterized. We characterized OsIRL protein using Northern, Western, 2‐DE, immunohistochemical analysis, and transgenic plant in rice. The transcript and proteins were more abundant in stems and roots than in flower and leaves. Expression of OsIRL was more accumulated in the root than in the shoot and seed. To investigate the release of reactive oxygen intermediates (ROI) by seed during germination, we utilized the apoplastic oxidation of 2¡‐,7¡‐dichlorofluorescin to fluorescent 2¡‐7¡‐dichloroflurescein and DAB staining as an in vivo assay. Expression of OsIRL was increased in the root elongation and maturation position carrying accumulation of ROI. Expression of OsIRL was increased in the oxidants (H2O2, FeCl3, MV) and decreased in the antioxidants such as reduced glutathione in the root and rice suspension cell. OsIRL was accumulated in the root sclerenchyma, outside of cortex, endodermis, and metaphloem cell. A certain concentration of H2O2 was necessary for root elongation, suggesting that OsIRL protein may play a role as antioxidant. The OsIRL transcripts levels were highly increased in callus, leaves, stem, and roots by treatment with ABA. The transgenic OsIRL plants have methyl viologen resistance, ROS‐generator, indicating that OsIRL have involved in root growth and resistance to oxidative stress.