Unveiling the Regulatory Role of miRNAs in Internode Elongation: Integrated Analysis of MicroRNA and mRNA Expression Profiles across Diverse Dwarfing Treatments in Maize (Zea mays L.)

MicroRNAs are crucial regulators of gene expression in maize. However, the mechanisms through which miRNAs control internode elongation remain poorly understood. This study engineered varying levels of internode elongation inhibition, revealing that dwarfing treatments diminished gibberellin levels, curtailed cell longitudinal growth, and slowed the rate of internode elongation. Comprehensive transcriptome and miRNA profiling of the internode elongation zone showed gene expression changes that paralleled the extent of the internode length reduction. We identified 543 genes and 29 miRNAs with significant correlations to internode length, predominantly within families, including miR164 and miR396. By incorporating target gene expression levels, we pinpointed nine miRNA-mRNA pairs that are significantly associated with the regulation of the internode elongation. The inhibitory effects of these miRNAs on their target genes were confirmed through dual-luciferase reporter assays. Overexpression of miR164h in maize resulted in increased internode and cell length, suggesting a novel genetic avenue for manipulating plant stature. These miRNAs may also serve as precise spatiotemporal regulators for in vitro plant development.