ZmADT2 regulates maize kernel development via the auxin signaling pathway

Arogenate dehydratase (ADT) catalyzes the final step in phenylalanine synthesis and is crucial for plant development and metabolism. Previously, we demonstrated that the ADT/prephenate dehydratase ZmADT2 is essential for maize resistance to Ustilago maydis and for overall plant development. In this study, we explored the role of ZmADT2 in maize kernel development. The mmsu mutant, a dysfunctional ZmADT2 variant, exhibits delayed embryo and endosperm development, along with deficiencies in carbohydrate and protein storage. Transcriptome analysis revealed differential expression of many kernel compartment-specific genes between mmsu and wild-type (WT) kernels, with impaired nutrient accumulation and auxin signaling pathway in the mmsu endosperm. Compared to WT, ZmADT2 mutation led to reduced auxin levels and smaller endosperm cell size. Exogenous auxin rescued the small kernel phenotype of mmsu . Additionally, auxin distribution was reduced in the basal endosperm transfer layer (BETL), causing defects in its development and function, including reduced transfer cell elongation, cell wall ingrowth and nutrient uptake. These findings suggest that ZmADT2 mediated mediates an auxin signaling pathway that is essential for maize kernel development.