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

Flowers are important reproductive organs of plants. The development of plant flowers depends on the activity of their inflorescence meristem (IM), and the impact of the spikelet structure determined by IM development on grain setting rate is an important factor in determining cereal crop yield. The developmental defects of florets and severe panicle failure have significantly reduced grain yield, but the related regulatory mechanisms are still unclear in foxtail millet. In this study, a stable abnormal spikelets development mutant of foxtail millet was obtained in the Jingu 21 (JG21) ethyl methylsulfonate (EMS) mutant library, which we named burned inflorescence (buin) because of the spikelets showed burned appearance. Compared with the wild type JG21, this mutant mainly exhibits burned inflorescence and semi-sterility, with mostly empty shells. To pinpoint the developmental stage of phenotypic divergence, we performed fluorescein diacetate-propidium iodide (FDA-PI) staining, which revealed that phenotypic abnormalities that began to appear during the AP stage. Subsequently, we conducted a comprehensive analysis of transcriptome data, including transcription factors, kinases, growth metabolism related hormones, and ROS metabolism related pathways, and identified a total of 2558 differentially expressed genes (DEGs). Based on the joint analysis of RNA-seq and BSA-seq, three candidate genes related to buin phenotype were ultimately identified, namely Seita.1G336800, Seita.1G335800, and Seita.1G338900. This study not only identified candidate genes that regulate spike development, but also laid a theoretical foundation for further understanding the development of florets in foxtail millet and other cereal crops.