Fine mapping and candidate gene analysis of tassel glume closure1 (tgc1) gene in maize (Zea mays L.)

The tassel glume closure1 (tgc1) mutant was identified and mapped, and ZmKAO1, which encodes an ent-kaurenoic acid oxidase, is the key candidate gene. Tassel glume timely opening is a key trait that influences cross-pollination and hybrid breeding. However, in maize (Zea mays L.), the related genes regulating this process remain largely unexplored. Here, we identified tassel glume closure1 (tgc1), a recessive mutant that exhibits tassel glume closure, anther non-extrusion, and no pollen shedding at the adult-plant stage. Anatomical and scanning electron microscopy (SEM) observations revealed that the tgc1 mutant phenotype is caused by the hindrance of filament elongation and lodicule swelling. We mapped the tgc1 locus and determined that Zm00001eb379120, which encodes ent-kaurenoic acid oxidase1 (ZmKAO1), is the key candidate gene of tgc1. Transcriptome analysis revealed that gibberellin (GA) biosynthesis was disrupted in tgc1 tassel, and exogenous application of GA₃ can fully rescue the tgc1 mutant phenotype. Based on the tgc1 mutant, we propose the novel Pseudo-Genic Male Sterility (GMS) Two-Line (PGTL) system for maize hybrid seed production. These findings enrich our understanding of ZmKAO1 function in tassel glume timely opening and provide a new germplasm resource and a promising technical approach for maize commercial hybrid seed production.