Molecular genetic basis of pod corn ( Tunicate maize)

Pod corn is a classic morphological mutant of maize in which the mature kernels of the cob are covered by glumes, in contrast to generally grown maize varieties in which kernels are naked. Pod corn, known since pre-Columbian times, is the result of a dominant gain-of-function mutation at theTunicate (Tu ) locus. Some classic articles of 20th century maize genetics reported that the mutantTu locus is complex, but molecular details remained elusive. Here, we show that pod corn is caused by acis -regulatory mutation and duplication of theZMM19 MADS-box gene. Although the WT locus contains a single-copy gene that is expressed in vegetative organs only, mutation and duplication ofZMM19 inTu lead to ectopic expression of the gene in the inflorescences, thus conferring vegetative traits to reproductive organs.