Gene mapping and candidate gene analysis of a sorghum sheathed panicle-I mutant

Panicle exsertion is essential for crop yield and quality, and understanding its molecular mechanisms is crucial for optimizing plant architecture. In this study, the sheathed panicle-I (shp-I) mutant was identified from the ethyl methane sulfonate mutant population of the sorghum [Sorghum bicolor (L.) Moench] variety Hongyingzi (HYZ). While phenotypically similar to the wild type during the seedling stage, shp-I exhibits a significantly shorter peduncle internode at the heading stage. Cytomorphological analysis revealed reduced parenchyma cell size within the mutant's peduncle internode. Phytohormonal profiling showed lower levels of indole-3-acetic acid and higher concentrations of brassinosteroid in the mutant compared to the wild type at the peduncle internode. Genetic analysis confirmed that the mutant phenotype was caused by a recessive single-gene mutation. Through bulked segregant analysis sequencing (BSA-seq) genetic mapping, the causative locus for the mutant phenotype was localized to a 59.65-59.92 Mb interval on chromosome 10, which contains 28 putative genes. Additionally, the gene SbiHYZ.10G230700, which encodes a BTB/POZ and MATH (BPM) domain protein, was identified as a candidate gene. Further analysis revealed that the non-synonymous mutations in the candidate gene were located within the MATH domain, affecting the 3D structure of the protein. In summary, this study provides a new genetic material and candidate genes for future research into the molecular regulation of sorghum peduncle length.