Identification and characterization of burned inflorescence (buin) mutant in foxtail millet

Flowers serve as critical reproductive organs in plants, with their development closely linked to the activity of the inflorescence meristem (IM). The structure of spikelets, which is determined by IM development, significantly influences the grain setting rate, thereby impacting cereal crop yield. Developmental defects in florets and severe panicle failure have been shown to markedly reduce grain yield; however, the regulatory mechanisms underlying these issues remain unclear in foxtail millet. In this study, we identified a stable mutant exhibiting abnormal spikelet development in the Jingu 21 (JG21) ethyl methylsulfonate (EMS) mutant library, which we named burned inflorescence (buin) due to the burnt appearance of the spikelets. Compared to the wild-type JG21, this mutant displays burned inflorescence and semi-sterility, characterized by predominantly empty shells. To determine the developmental stage at which phenotypic divergence occurs, we employed fluorescein diacetate-propidium iodide (FDA-PI) staining, revealing that phenotypic abnormalities began to manifest during the bristle primordium meristem (BP) stage. Subsequently, we conducted a comprehensive analysis of transcriptome data, encompassing transcription factors, kinases, hormones related to growth metabolism, and pathways associated with ROS, and identified a total of 2558 differentially expressed genes (DEGs). Through the combined analysis of RNA-seq and BSA-seq, we identified three candidate genes related to buin phenotype, namely Seita.1G336800, Seita.1G335800, and Seita.1G338900. This study not only identified candidate genes that regulate spike development but also establishes a theoretical foundation for further elucidating development of florets in foxtail millet and other cereal crops.