A genetic and phenotypic characterization of theearly phase change mutation in maize

Vegetative development in maize is divided into two distinct phases that can be distinguished by morphological, histochemical and genetic markers. In maize, leaves formed during the juvenile phase produce epicuticular wax, lack epidermal hairs, and have rounded epidermal cells with thin cuticles. Leaves made during the adult phase lack wax, have epidermal hairs, and have rectangular epidermal cells with thick cuticles. During the switch from juvenile to adult development there is a transition zone in which the shoot produces leaves that express traits specific to both phases. Here I present a phenotypic and genetic analysis of the early phase change (epc) mutation. In epc plants leaves expressing juvenile traits are reduced in number while the number of leaves with adult characteristics is not altered. epc mutants flower at the same time as wild type and the rate of leaf formation during embryogenesis is not affected. However, immediately after germination, there is a brief pause in leaf initiation in epc plants which accounts for the fact that flowering time is not affected. epc maps to the long arm of chromosome 8. It is epistatic to the phase specific aspects of Teopod, viviparous8, and dwarf. This analysis of the epc mutations suggests that EPC plays a crucial role in maintaining the juvenile phase and acts downstream of these genes