Analysis of Differentially Expressed Rice Genes Reveals the ATP-Binding Cassette (ABC) Transporters as a Candidate Gene Against the Sheath Blight Pathogen, Rhizoctonia solani

Sheath blight is a serious rice disease worldwide and genes involved in resistance remain unclear. In the present study, a virulent field isolate of Rhizoctonia solani was used to inoculate detached leaves of a sheath blight resistant rice cultivar ‘Jasmine 85’, a suppression subtractive cDNA library was constructed using RNA isolated 16 hours post inoculation (hpi), and differentially expressed genes were identified from the cDNA library. A total of 159 uniquely expressed sequence tags were identified, including 105 from rice with enrichment in categories related to cellular response, molecular signaling and host defense. Coupled with gene expression studies by DNA microarray, 27 highly induced genes involved in signal transduction and defense responses were identified within 16 hpi. Three members of the ABC transporter gene family (OsABC1, OsABC9 and OsABC12) encoding pleiotropic drug resistance (PDR)-like ATP binding cassette (ABC) transporters were mapped to different sheath blight resistance QTL and their differential expressions were validated. Three high-resolution melting (HRM) markers were developed from these ABC gene family members to distinguish alleles between sheath blight susceptible cultivar ‘Lemont’ and resistant cultivar ‘Jasmine 85’. Association of sheath blight resistance to these HRM markers was examined in 77 recombinant inbred lines derived from the cross between ‘Jasmine 85’ and “Lemont”. The OsABC9 gene located in a major sheath blight resistance QTL qShB9-2 showed a major contribution to sheath blight resistance. These results are useful for marker assisted section and functional validation of the ABC genes in sheath blight disease resistance.