ZmEHD1 is required for kernel development and vegetative growth through regulating auxin homeostasis.

The roles of C-terminal Eps15 homology domain (EHD) proteins in clathrin-mediated endocytosis (CME) in plants are poorly understood. Here, we isolated a maize (Zea mays) mutant, designated as ehd1, which showed defects in kernel development and vegetative growth. Positional cloning and transgenic analysis revealed that ehd1 encodes an EHD protein. Internalization of the endocytic tracer FM4-64 was substantially reduced in the ehd1 mutant and ZmEHD1 knock-out mutants. We further demonstrated that ZmEHD1 and ZmAP2 σ subunit physically interact at the plasma membrane. Auxin distribution and ZmPIN1a-YFP localization were altered in the ehd1 mutant. Kernel IAA levels were substantially lower in the ehd1 mutant than in wild-type maize. Exogenous application of 1-NAA, but not GA3 or 2-NAA, rescued the seed germination and seedling emergency phenotypic defects of ehd1 mutants. Taken together, these results indicate that ZmEHD1 regulates auxin homeostasis by mediating CME through its interaction with the ZmAP2 σ subunit, which is crucial for kernel development and vegetative growth of maize.