Functional validation of OsRPM1 as a positive regulator of bacterial blight resistance in rice via virus-induced gene silencing.

Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is a major constraint to rice production in humid tropical regions. In the search for new genetic sources of resistance, we focused on OsRPM1 (LOC Os12g30070.1), a rice gene encoding a coiled-coil nucleotide-binding leucine-rich repeat (CC-NB-LRR) protein, structurally similar to well-characterized resistance (R) proteins in Arabidopsis and other plant species. Although its role in rice immunity was previously uncharacterized, transcriptomic profiling revealed that OsRPM1 is significantly upregulated in a type III secretion system (T3SS)-dependent manner during infection with the virulent Xoo race 4, suggesting a pathogen-responsive defence function. To evaluate this, we employed virus-induced gene silencing (VIGS) to transiently suppress its expression in rice. Silencing OsRPM1 increased susceptibility to Xoo, resulting in more severe disease symptoms, reduced reactive oxygen species (ROS) accumulation, and impaired callose deposition; key defence responses linked to effective resistance. These findings demonstrate that OsRPM1 acts as a positive regulator of rice defence and support its potential as a candidate for broad-spectrum, durable resistance breeding.