Functional analysis and breeding application of the ZmDLE1 for maize plant height.

Plant height (PH) and ear height (EH) are critical agronomic traits in maize breeding, directly affecting lodging resistance, mechanical harvesting, and yield potential. In this study, we identified a stable dwarf and low ear mutant, zmdle1-1, from an EMS-mutagenized population of the inbred line LY8405. Genetic mapping and allelism tests, together with a single nucleotide variant mutant (zmdle1-2) and a CRISPR-Cas9 knockout mutant (zmdle1-3), confirmed that the candidate gene ZmDLE1 (Zm00001d033231), which encodes Expansin-B4, is responsible for the reduced PH and EH. Compared with wild-type plants, zmdle1 mutants showed 35% lower PH and 63% lower EH, primarily due to a decreased number of internodes below the ear and shortened internode length. Transcriptome analysis revealed differential expression of hormone responsive genes, and exogenous hormone treatments demonstrated that GA₃, IAA and BR could promote PH in the mutant. Endogenous hormone measurements showed significantly reduced GA₁ and GA₃ levels in the mutant, suggesting that ZmDLE1 may regulate PH through GA biosynthesis or signaling. Importantly, when zmdle1-1 was crossed with five elite inbred lines, the resulting hybrids consistently exhibited markedly reduced PH and EH without compromising ear morphology or yield-related traits. Collectively, our findings establish ZmDLE1 as a key regulator of maize plant architecture and provide a valuable dwarfing resource for breeding high-density tolerant and mechanically harvestable maize hybrids.