Abstract
Plants depend heavily on Resistance (R) proteins, many encoding leucine-rich repeat nucleotide-binding site (NLR) proteins, essential for mediating targeted defense against pathogens. In rice, NLR proteins are pivotal immune receptors in combating Magnaporthe oryzae-triggered rice blast. However, the precise molecular mechanism underlying how R proteins regulate downstream signaling remains elusive due to the lack of knowledge regarding their direct downstream targets. Pigm-1, a new allele of PigmR, was cloned from Shuangkang 77009 in our laboratory. This study reveals OsRac1, a GTPase, as a signaling molecule involved in Pigm-1-mediated blast resistance, suggesting its potential as a common downstream effector of rice NLR proteins. Additionally, we identified RAI1, a transcriptional activator, as an essential Pigm-1 interactor for blast resistance. The NBS domain of Pigm-1 facilitates its binding to and activation of OsRac1, while the CC domain enables its binding to and activation of RAI1, ultimately inducing cell death. Furthermore, this research demonstrates that molecular marker-assisted selection technology enhances both resistance and yield in the crucial two-line restorer 9311(Pigm-1). This study offers crucial insights into how diverse NLR proteins activate downstream molecules and serves as a valuable reference for molecular breeding of rice blast resistance genes, particularly Pigm-1.