This research analyzes gibberellin (GA) biosynthesis in relation to shoot growth in maize. The approach combines the disciplines of chemistry (organic synthesis), biochemistry (radiolabelled feeds and enzymology) and genetics (molecular and physiological). The specific goals of this research are to use GA mutants (and normals): (1) to analyze gene expression in callus tissue cultures; (2) to identify maize GA conjugates and analyze conjugation in seedlings; (3) to correlate levels of GA1 with the short and intermediate alleles of d1 mutant seedlings; (4) to locate the steps in the GA biosynthetic pathway blocked by the d2, d3 and an1 mutants; (5) to analyze the biosynthetic origin of GA3 in maize shoots from feeding studies with labelled GA4, GA7 and 2,3-dehydro-GA9; (6) to study the properties of normal and mutant hydroxylase, the enzyme controlling the step GA20 to GA1; (7) to continue preliminary studies on cloning the dwarfing genes; and (8) to continue classical genetic studies with mutants of maize concerned with GA metabolism. GAs are plant hormones that regulate many plant responses including shoot elongation. In maize, plants lacking endogenous GA1 possess a dwarf habit of growth. Five dwarf mutants (GA mutants) are used to unravel details of the GA biosynthetic pathway, and to define the role of specific GAs in the control of GA dependent shoot elongation.
