ZmEHD1 Is Required for Kernel Development and Vegetative Growth through Regulating Auxin Homeostasis

Abstract

The roles of C-terminal Eps15 homology domain (EHD) proteins in clathrin-mediated endocytosis in plants are poorly understood. Here, we isolated a maize (<i>Zea mays</i>) mutant, designated <i>ehd1</i>, which showed defects in kernel development and vegetative growth. Positional cloning and transgenic analysis revealed that <i>ehd1</i> encodes an EHD protein. Internalization of the endocytic tracer FM4-64 was substantially reduced in the <i>ehd1</i> mutant and <i>ZmEHD1</i> knockout mutants. We further demonstrated that ZmEHD1 and the ZmAP2 σ subunit physically interact at the plasma membrane. Auxin distribution and ZmPIN1a-YFP localization were altered in the <i>ehd1</i> mutant. Kernel indole-3-acetic acid levels were substantially lower in the <i>ehd1</i> mutant than in wild-type maize. Exogenous application of 1-naphthaleneacetic acid, but not GA₃ or 2-naphthaleneacetic acid, rescued the seed germination and seedling emergency phenotypic defects of <i>ehd1</i> mutants. Taken together, these results indicate that ZmEHD1 regulates auxin homeostasis by mediating clathrin-mediated endocytosis through its interaction with the ZmAP2 σ subunit, which is crucial for kernel development and vegetative growth of maize.