The objective of this project is to characterize genetic control of the transition, termed "phase change", from juvenile to adult vegetative growth habit in maize. This attempt to dissect genetic regulation of the temporal gene expression program will be accomplished via analysis of mutations (Tp1, Tp2 and Tp3) that prolong the juvenile growth phase. The function of these mutations will be investigated by study of the autonomy of their expression, and their effect on maize leaf growth, morphology and cell lineage. The phenotypes and genetic interactions of putative loss.of.function derivatives of the primary mutations will be characterized as an additional approach to definition of their function. Information from these studies will be used to evaluate growth transition models which involve: 1) overlapping juvenile and adult programs; and 2) sequential, mutually exclusive juvenile and adult programs. This study has the potential to advance fundamental knowledge of the genetic control of maize development, and possible pathways of its evolution.
