The OsOXO2, OsOXO3 and OsOXO4 Positively Regulate Panicle Blast Resistance in Rice

Although panicle blast is more destructive to yield loss than leaf blast in rice, the cloned genes that function in panicle blast resistance are still very limited and the molecular mechanisms underlying panicle blast resistance remain largely unknown.

In the present study, we have confirmed that the three Oxalate oxidase (OXO) genes, OsOXO2, OsOXO3 and OsOXO4 from a blast-resistant cultivar BC10 function in panicle blast resistance in rice. The expression of OsOXO2, OsOXO3 and OsOXO4 were induced by panicle blast inoculation. Subcellular localization analysis revealed that the three OXO proteins are all localized in the nucleus and cytoplasm. Simultaneous silencing of OsOXO2, OsOXO3 and OsOXO4 decreased rice resistance to panicle blast, whereas the OsOXO2, OsOXO3 and OsOXO4 overexpression rice plants individually showed enhanced panicle blast resistance. More H₂O₂ and higher expression levels of PR genes were observed in the overexpressing plants than in the control plants, while the silencing plants exhibited less H₂O₂ and lower expression levels of PR genes compared to the control plants. Moreover, phytohormone treatment and the phytohormone signaling related gene expression analysis showed that panicle blast resistance mediated by the three OXO genes was associated with the activation of JA and ABA signaling pathways but suppression of SA signaling pathway.

OsOXO2, OsOXO3 and OsOXO4 positively regulate panicle blast resistance in rice. The OXO genes could modulate the accumulation of H₂O₂ and expression levels of PR gene in plants. Moreover, the OXO genes mediated panicle blast resistance could be regulated by ABA, SA and JA, and may be associated with the activation of JA and ABA signaling pathways but suppression of the SA signaling pathway.