Mapping and Gene Mining of the Lobed Leaf Trait in Mustard

Mustard (Brassica juncea), an essential leaf and oil crop in China, exhibits notable yield potential and adaptability, both of which are influenced by the morphology of the leaf margin. Despite its agronomic importance, the genetic regulatory mechanisms governing this trait remain poorly understood, posing a challenge to molecular breeding efforts. In this study, mustard varieties with lobed and non-lobed leaf margins were used to systematically investigate the genetic basis of leaf margin differentiation through BSA-seq, RNA-seq, and bioinformatics analyses. BSA-seq screening identified four LMI1 homologous genes, including BjuOA10G33260, which may fissure the leaf margin by suppressing cytokinin signaling. RNA-seq analysis revealed significant enrichment of ethylene and growth hormone pathways during key stages of leaf development (at 12 days post-sowing). Integrated analysis of BSA-seq and RNA-seq data identified 15 genes involved in leaf morphogenesis, including BjuOB05G34700 (ADF4, an actin depolymerization factor), BjuOA08G35830 (GATA transcription factor 11), BjuOA09G42060 (ERF transcription factor), and BjuOA07G29650 (GATA transcription factor). Notably, BjuOA10G30380 (TGA2) and BjuOA10G34680 (LAX1) may regulate cytoskeletal dynamics and hormonal signaling, contributing to the development of leaf morphology. This study presents the first molecular network regulating the morphogenesis of the leaf edge in mustard, offering a theoretical foundation and valuable genetic resources for breeding new varieties with optimized leaf architecture.