-like Transposon Elements Inserted in Cause Male Sterility in Maize.

Using male sterile (MS) lines instead of normal inbred maternal lines in hybrid seed production can increase the yield and quality with lower production costs. Therefore, developing a new MS germplasm is essential for maize hybrid seed production in the future. Here, we reported a male sterility gene , cloned from a newly found MS mutant . This mutant has an underdeveloped tassel that showed impaired glumes and shriveled anthers without pollen grains. The MS locus of was mapped precisely to a 112-kb-interval on the chromosome 5. This interval contains only three candidate genes, , , and . Sequencing results showed that only candidate harbored a 548-bp transposable element (TE) in its 9th exon, and the two other candidate genes were found to have no genetic variations between the mutant and wild type (WT). Thus, is the only candidate gene for male sterility of the mutant . In addition, we screened another recessive MS mutant, , which exhibited similar male sterility phenotypes to . Sequencing in showed a 600-bp TE located in its 2nd exon. encodes an ATP-binding cassette in the G subfamily of ABC (ABCG) transporters, , with both mutants which harbored an -like transposon in each. To verify the function of for male sterility further, we found an ethyl methanesulfonate (EMS) mutant, , which displayed male sterility and tassel phenotypes highly similar to and , confirming that must be the gene for male sterility in maize. In addition, the results of lipid metabolome analysis of young tassels showed that the total lipid content of the mutant was significantly lower than that of the WT, with 15 subclasses of lipids, including PE (phosphatidylethanolamine), PC (phosphatidylcholine), DG (digalactosyldiacylglycerols), and MGDG (monogalactosyldiacylglycerol) which were significantly down-regulated in the mutant versus its wild type. In summary, we identified alternate mutations of the gene, which may be a potential germplasm for hybrid seed production in maize.