Maize STEM BENDING1 controls plant architecture through cell wall and auxin pathways

Crop yield is largely determined by plant architecture. Identifying the key genes responsible for maize architecture can help optimize plant architecture for high-density planting. Here, we characterized a dominant stem bending mutant (Stb1) in maize, which exhibited bent stems and curved leaves leading to a slanted architecture. Genetic mapping delimited Stb1 to a 3.7 Mb interval on chromosome 1. Transcriptome analysis suggested that Stb1 mutation impaired the molecular pathways related to cell wall components and environmental stimuli. Consistently, lignin and hemicellulose contents were altered between the convex side and concave side of Stb1 stems. In addition, the shoot gravitropism regulator LAZY1 transcripts and endogenous auxin levels were differentially accumulated between the two sides of Stb1 stems. Our study reveals that STB1 plays a role in maintaining upright stems through cell wall and auxin-related pathways, providing a new target for optimizing maize shoot architecture.