Identification of a locus associated with genic male sterility in maize via EMS mutagenesis and bulked-segregant RNA-seq

Genic male sterility (GMS) is one of the most important resources for exploiting heterosis in crop breeding, so that identifying genomic loci regulating GMS is desirable. However, many regulatory genes controlling GMS have not yet been characterized in maize, owing partly to a lack of genetic materials. We generated a recessive male-sterile maize mutant in the Jing 724 genetic background via ethyl methanesulfonate treatment, and found the male sterility to be due to a single gene mutation. Bulk-segregant RNA sequencing of three replicates indicated that one genomic region located at the end of chromosome 4 was associated with the observed mutant phenotype. Among genes with nonsynonymous mutations, Zm00001d053895 (bHLH51) showed abolished expression in the sterile bulks and was annotated as a bHLH transcription factor orthologous to Arabidopsis AMS, suggesting an association with the male sterility of the mutant. Kompetitive Allele-Specific PCR assays further validated the exclusive correlation of male sterility with the single C-to-T mutation in the fifth exon. The new maize mutant and the potential SNP locus provide novel genetic material for investigating the molecular mechanism underlying tapetal development and may facilitate the improvement of hybrid production systems.