A Cytosolic Triosephosphate Isomerase Is a Key Component in XA3/XA26-Mediated Resistance.

Bacterial blight caused by pv () causes severe damage to rice () production worldwide. The major disease resistance gene, , confers broad-spectrum and durable resistance to at both seedling and adult stages. However, the molecular mechanism of the -initiated defense pathway against is still largely unknown. Here, we show that a triosephosphate isomerase (TPI), OsTPI1.1, is a key component in XA3/XA26-mediated resistance to OsTPI1.1 is a glycolytic enzyme that catalyzes the reversible interconversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate. Transcriptional suppression of in plants harboring largely impaired the XA3/XA26-mediated resistance to , and constitutive overexpression of in susceptible rice plants without only slightly decreased the susceptibility to Therefore, both XA3/XA26 and OsTPI1.1 are required in XA3/XA26-mediated resistance. We show that OsTPI1.1 participates in the resistance through its enzymatic activity, which was enhanced significantly by its binding with XA3/XA26. Reactive oxygen species (ROS), especially hydrogen peroxide, accumulated in the OsTPI1.1-overexpressing plants, and suppression of decreased ROS accumulation. The changes in ROS are associated with the reduction of NADP to NADPH, which may act as a redox cofactor to scavenge ROS, leading to reduced resistance to These results suggest that OsTPI1.1 modulates ROS production as a resistance mechanism against .