Characterization of a Novel NBS-LRR Gene Involved in Bacterial Blight Resistance in Rice

Nucleotide-binding site leucine-rich repeat (NB-LRR) genes play important roles in plant disease resistance. Due to its similarity to Rp1 in maize (Zea mays), a novel NB-LRR gene was isolated from rice and designated as OsRP1L1 (Oryza sativa Rp1-like 1). Analysis of expression of a super green fluorescent protein (sGFP) fusion gene revealed that the OsRP1L1 protein localizes to the nucleolus. Expression patterns suggested that OsRP1L1 was involved in responses to several plant growth regulators (PGRs) and environmental stresses. To explore its function in bacterial blight (BB) resistance, OsRP1L1 was cloned and overexpressed in a susceptible japonica rice cultivar. Overexpression of OsRP1L1 moderately elevated the resistance of plants to Xanthomonas oryzae pv. oryzae strains PXO86 and PXO341. Transcriptome analysis showed that plants overexpressing OsRP1L1 had small changes in their transcriptome, with 26 genes showing statistically significant changes of more than two-fold. The most up-regulated transcripts-a DIN1-like gene and a terpene synthase (TPS) gene-were up-regulated 7.9- and 7.6-fold, respectively. It was also noted that seven of the up-regulated genes have also reportedly been induced by overexpression of OsbZIP46, which has been identified recently as a player in ABA sensing. All these findings suggest that OsRP1L1 plays an important role in rice BB resistance, and may be useful as a genetic resource for engineering disease resistance in plants.