Fine mapping and candidate identification of SST , a gene controlling seedling salt tolerance in rice ( Oryza sativa L.)

Using a recessive mutant with enhanced salt tolerance at seedling stage obtained from an indica rice cultivar R401 by gamma-ray irradiation, a novel gene controlling salt tolerance in rice was previously mapped to a 406-kb region on chromosome 6. We named the gene Seedling Salt Tolerance ( SST ). In this study, with a large F 2 population derived from a cross between mutant sst and a japonica cultivar Nipponbare (salt sensitive), SST was further fine mapped to a 17-kb interval between InDel markers ID27101 and ID27118, in which only one gene ( OsSPL10 ) was predicted. Sequencing analysis indicated that the 232nd base of the coding sequence of OsSPL10 was deleted in the sst allele, resulting in a frameshift mutation. The result strongly suggested that OsSPL10 should be the candidate of SST . OsSPL10 is a member of the SBP-box gene family. This is the first time that the SBP-box gene family is found to be probably involved in the regulation of seedling salt tolerance in plant.