During shoot growth all plants progress through morphologically and physiologically distinct juvenile and adult developmental phases. The mechanism regulating the expression of these phases and the transition from one phase to another is poorly understood, particularly in herbaceous plants where the juvenile phase is often brief. The Teopod (Tp) mutations of maize prolong the expression of juvenile traits, and thereby provide an opportunity to study the genetic basis of phase change in a herbaceous species. To determine the function of these genes it is necessary to identify their products and study how they are expressed during shoot growth. Ac-induced mutations of Tp2 will be identified and used to clone this gene. The structure and the sequence of this gene will be determined and transcribed regions of the locus will be used as probes to study its expression in both normal and mutant plants. These experiments will initially be performed by Northern analysis and later by in situ hybridization. To facilitate the cloning and genetic analysis of both this and the other Tp genes, an RFLP map of the region surrounding each gene will be constructed. The function of the Tp loci will also be studied by determining their effect on the expression of genes whose expression is normally limited to either the juvenile or adult phase of shoot growth. These latter studies will reveal whether the character of the shoot is determined by a series of sequential programs, or in a combinatorial fashion by parallel developmental programs.
