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 signifi-cant 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 inter-action 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.

LMM5.1 and LMM5.4,two eukaryotic translation elongation factor 1Alike gene family members,negatively affect cell death and disease resistance in rice

Lesion mimic mutant（LMM） genes, stimulating lesion formation in the absence of pathogens, play significant roles in immune response. In this study, we characterized a rice lesion mimic mutant, lmm5,which displayed light-dependent spontaneous lesions. Additionally, lmm5 plants exhibited enhanced resistance to all of the tested races of Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae（Xoo） by increasing the expression of defense-related genes and the accumulation of hydrogen peroxide. Genetic analysis showed that the lesion mimic phenotype of lmm5 was controlled by two genes, lmm5.1 and lmm5.4, which were isolated with a map-based cloning strategy. Remarkably, LMM5.1 and LMM5.4 share a 97.4% amino acid sequence identity, and they each encode a eukaryotic translation elongation factor 1A（e EF1A）-like protein. Besides, LMM5.1 and LMM5.4 were expressed in a tissue-specific and an indicaspecific manner, respectively. In addition, high-throughput m RNA sequencing analysis confirmed that the basal immunity was constitutively activated in the lmm5 mutant. Taken together, these results suggest that the homologous e EF1A-like genes, LMM5.1 and LMM5.4, negatively affect cell death and disease resistance in rice.