dizzy1 coordinates shoot and root development, constitutive stress responses, and phytohormone signaling in maize

Abstract

We identified the monogenic recessive maize (Zea mays L.) mutant dizzy1 in a segregating F2-family by a forward genetic screen of the BonnMu population, a sequence-indexed collection of Mutator transposon-induced mutants. dizzy1 exhibits a dwarf phenotype with pronounced twisting of leaves and roots. Histological analyses revealed irregular cell organization in dizzy1, including enlarged upper epidermal cells in leaves and disorganized cortical cell architecture in roots. Physiological analysis of primary roots indicated reduced cell viability, reflected by increased membrane permeability and altered metabolic activity. Hormone response assays further showed that dizzy1 is insensitive to brassinolide, exhibits a delayed auxin-promoted shoot response, and displays altered gibberellin effects on lateral root development. Bulked segregant RNA sequencing mapped the dizzy1 locus to chromosome 2. Comparative transcriptome profiling of primary roots identified 4,378 differentially expressed genes between wild type and dizzy1, revealing widespread transcriptional reprogramming. Consistent with functional enrichment analyses, histochemical and spectrophotometric assays indicated elevated reactive oxygen species and increased lignin in diz1 primary roots. These findings define dizzy1 as a pleiotropic developmental mutant linking hormone signaling, redox homeostasis, and cell wall regulation in maize growth.