Identification of a dominant genic male-sterility gene derived from the rice cultivar ‘Lebed’

Abstract

Dominant genic male sterility (GMS) is a powerful tool for implementing outcross-based breeding systems in self-pollinated crops such as rice (Oryza sativa L.). We previously identified male sterile plants in an indica rice cultivar ‘Lebed’, backcrossed with the japonica cultivar ‘Taichung 65’ (T65), and showed that the ‘Lebed’ allele of a male sterility gene, designated LEBED-TAICHUNG 65 MALE STERILITY (LTMS), functions as a dominant sporophytic pollen killer in the T65 genetic background. In this study, we performed map-based cloning of the LTMS gene. The LTMS locus was delimited to a 144-kb region of the ‘Lebed’ genome. Among nine predicted genes in this region, four were expressed in anthers and three exhibited sequence polymorphism between the T65 and ‘Lebed’ alleles. Genomic fragments containing each ‘Lebed’ allele were independently introduced into T65. Transgenic plants carrying the ‘Lebed’ allele of LOC_Os10g22180 displayed stunted anthers and shrunken pollen grains, characteristic of the LTMS phenotype. LOC_Os10g22180 was found to encode a 146–amino-acid protein of unknown function, whereas the T65 allele encoded a 118–amino-acid protein. Both proteins contain predicted nuclear localization signals. These results demonstrate that LTMS corresponds to the ‘Lebed’ allele of LOC_Os10g22180 and functions as a dominant GMS gene in the japonica nuclear background, suggesting that the LTMS line may be a valuable resource for recurrent selection in outcross-based breeding of japonica rice.