Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The development of maize embryos from 15 DAP until maturation, at approximately 50 DAP, has been examined at the level of gene expression. Three subsets of embryonic polypeptides have been identified. Subset 1 exhibits little or no variation during the period of study. Subset 2 is prominent in the earlier stages of development but shows reduced relative levels of synthesis as the embryo matures. Subset 3 exhibits novel and/or enhanced synthesis during the later stages of development. Some polypeptides among subsets 1 and 2 appear to show tissue specificity in the seedling and maturing plant indicating that molecular differentiation has occurred in the embryo. All polypeptides of subset 3 appear to be embryo specific.;Results obtained from plants grown in different field seasons and under greenhouse conditions indicated that environmental conditions can significantly influence the growth and development of maize embryos. More rapid growth and development were correlated with increased temperatures. Similar patterns of growth and development were observed for 2 inbred cultivars of maize and the hybrids derived from their reciprocal crosses. Differences detected between inbreds appeared to be heteroallelic since the products of both parents were expressed in the reciprocal hybrids.;Comparison of polypeptides synthesized in situ with those translated in vitro from total cellular and polysomal RNA indicated that reduction in synthesis of many subset 2 polypeptides is accompanied by a decrease in the relative abundance of their mRNAs. Differences between in situ and in vitro patterns suggested that the expression of many subset 3 polypeptides may be under translational and/or post-translational control. The absence of translatable free polysomes in 52 DAP embryos may be indicative of the general shut-down in embryo metabolism associated with maturation.



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