Developing plant embryos have the capacity to germinate or to mature. Dr. Rivin is investigating how embryo abscisic acid level, hormone sensitivity and changing water relations modulate the expression of these two developmental potentials. Her goals are to define, at the molecular level, the developmental pathways that are modulated by these physiological cues during maize embryo maturation, and to identify the genetic mechanisms that regulate their expression. To address this problem she will follow a three part program that involves both molecular and genetic approaches, focussing on mutants that fail to develop successfully through maturation phase. The specific objectives are the following: 1) Identify cDNA clones of mRNAs that are specific to embryo maturation, using her previous observations about the synthesis of maturation phase polypeptides in wild type and viviparous mutants as a basis for selection of co-regulated message sets. 2) Measure the expression of maturation mRNAs during normal maize embryogenesis and examine how this program is altered when development is disrupted genetically in viviparous and defective kernel mutants, or by manipulation of physiological factors in tissue culture. 3) Search for new transposon tagged embryo lethal mutants to collect additional loci for genetic dissection of embryo maturation, and to provide a means of cloning genes essential to embryo development. %%% In flowering plants the developing seed creates a morphologically complete embryo which goes on eventually to germinate. Embryo development takes place in two stages, the second of which is termed maturation. This project is aimed at an understanding of the factors that control this maturation process.
