TaEPFL1 gene controls the development of wheat pistils and stamens by regulating ethylene synthesis

Proper development of floral organs is essential for reproductive success and grain yield in wheat. However, the molecular mechanisms regulating wheat floral organ development remain largely unknown. In this study, we characterized the role of the wheat TaEPFL1 gene in floral organ development and its association with ethylene signaling. TaEPFL1 was highly expressed in immature spikes of the pistillody mutant HTS-1, particularly during the pistil and stamen specification stages. Its expression was responsive to both exogenous ethylene and the ethylene inhibitor 1-Methylcyclopropene (1-MCP). Overexpression of TaEPFL1 in transgenic wheat led to shortened stamens, defective pistils, male sterility, and complete reproductive failure. Histological analysis revealed delayed tapetum degradation, indicating disrupted programmed cell death (PCD). Gas chromatography (GC) showed significantly reduced ethylene production and release in TaEPFL1-overexpressing lines. Similar floral defects were observed in wild-type plants treated with 1-MCP. Transcriptome and qRT-PCR analyses further confirmed downregulation of multiple ethylene biosynthesis-related genes, including three homologs of TaACO. These results suggest that TaEPFL1 negatively regulates ethylene biosynthesis by repressing TaACO expression, thereby impairing floral organ differentiation. We propose a feedback model in which ethylene induces TaEPFL1, which in turn suppresses ethylene production to maintain hormonal homeostasis. This study reveals a novel regulatory mechanism linking TaEPFL1 to ethylene-mediated floral development and provides new insights for improving wheat fertility through molecular breeding.