A Rice NBS-ARC Gene Conferring Quantitative Resistance to Bacterial Blight Is Regulated by a Pathogen Effector-Inducible miRNA.

The bacterium Xanthomonas oryzae pv. Oryzae (Xoo) causes blight in rice worldwide, resulting in significant crop loss. However, no gene underlying a quantitative trait locus (QTL) for resistance against Xoo has been cloned yet. Here, we report the map-based cloning of a QTL, in which the NBS8R gene confers quantitative resistance to Xoo. NBS8R encodes an NB-ARC protein, which is involved in pathogen/microbe-associated molecular pattern-triggered immunity and whose expression is regulated by non-TAL effector XopQ-inducible Osa-miR1876 through DNA methylation. Sequence analysis of NBS8R in wild rice species and rice cultivars suggests that the Osa-miR1876 binding sites in the 5' UTR of NBS8R are inserted by chance and have undergone variations with Osa-miR1876 throughout evolution. The interaction between NBS8R and XopQ-inducible Osa-miR1876 is partially in keeping with the zigzag model, revealing that quantitative genes may also follow this model to control the innate immune response or basal disease resistance, and may prove valuable in utilizing the existing landraces that harbor the NBS8R gene but with no Osa-miR1876 binding site in rice breeding for bacterial blight resistance.