SUMMARY

Bacterial leaf streak (BLS) is a major bacterial disease of rice. Utilization of host genetic resistance has becomeone of the most important strategies for controlling BLS. However, only a few resistance genes have been char-acterized. Previously, a recessive BLS resistance genebls1was roughly mapped on chromosome 6. Here, we fur-ther delineatedbls1to a 21 kb region spanning four genes. Genetic analysis confirmed that the gene encoding amitogen-activated protein kinase (OsMAPK6) is the target of the allelic genesBLS1andbls1. Overexpression ofBLS1weakened resistance to the specificXanthomonas oryzaepv.oryzicola(Xoc) strain JZ-8, while low expres-sion ofbls1increased resistance. However, both overexpression ofBLS1and low expression ofbls1couldincrease no-race-specific broad-spectrum resistance. These results indicate thatBLS1andbls1negatively regulaterace-specific resistance toXocstrain JZ-8 but positively and negatively control broad-spectrum resistance, respec-tively. Subcellular localization demonstrated thatOsMAPK6was localized in the nucleus.RGA4,whichisknownto mediate resistance toXoc, is the potential target ofOsMAPK6. Overexpression ofBLS1and low expression ofbls1showed increase in salicylic acid and induced expression of defense-related genes, simultaneously increasingbroad-spectrum resistance. Moreover, low expression ofbls1showed increase an in jasmonic acid and abscisicacid, in company with an increase in resistance toXocstrain JZ-8. Collectively, our study provides new insightsinto the understanding of BLS resistance and facilitates the development of rice host-resistant c*rs.