The miR164e–NAC32 module orchestrates maize plant height via post-translational regulation of DELLA protein stability

Optimization of plant architecture requires precise regulation of internode elongation; however, the post-translational mechanisms that integrate microRNA and phytohormone signaling remain poorly understood. Here, we describe a hierarchical miR164e-NAC32-DELLA regulatory network that controls stem development in maize. Genetic analyses demonstrate that ZmmiR164e negatively regulates its target gene ZmNAC32, with ZmmiR164e overexpression enhancing internode cell elongation and loss-of-function resulting in dwarfism. Notably, ZmNAC32 physically interacts with and stabilizes the DELLA protein ZmD8, as evidenced by increased ZmD8 protein levels in ZmNAC32-overexpressing plants compared with the wild type. Transcriptome profiling reveals that ZmNAC32-mediated regulation of plant height occurs primarily through post-translational stabilization rather than extensive transcriptional reprogramming, with downstream cell wall biosynthesis genes (EXP, XTH, and LAC) showing GA-responsive suppression. Structural analyses further reveal that ZmNAC32 binding stabilizes ZmD8 by shielding the key interaction residue K399, thereby suppressing its degradation. Together, these results identify a miRNA-NAC-DELLA module that governs post-translational protein stability during stem development and provides strategic targets for precision breeding of plant architecture.