The general objective of this research is to develop an understanding of the mechanisms of regulation of the biosynthesis of diterpenoid substances of physiological importance in the life of the plant. The first experimental target is kaurene synthetase, a key regulatory enzyme in the biosynthetic pathway leading to the gibberellin family of plant hormones. A new approach to assessing the levels of this activity is being attempted. Components of the kaurene synthetase complex will be purified to homogenity, antibodies prepared and cDNA clones isolated. These tools will then be utilized to measure the levels of translatable and total hybridizable kaurene synthetase mRNAs in plant organs, and their changes under different physiological circumstances. The biosynthetic pathways involved in diterpenoid phytoalexin biosynthesis in rice (Oryza sativa) is a second area of interest. The biochemical characteristics of these biosynthetic pathways will be further defined. The nature of elicitor molecules that initiate diterpenoid phytoalexin biosynthesis will be investigated. And the role of transcriptional regulation in the expression of the enzymes involved in cyclization of diterpene hydrocarbon intermediates will be investigated. These results will contribute to our knowledge of the manner in which plants respond to environmental and biological stresses.%%% Cyclic diterpenoid metabolites are often characterized as secondary metabolites. Such substances appear to serve the organism that produces them in specialized regulatory roles that enable the organism to adapt to environmental changes and biological stresses associated with encroachments by pathogens, predators and competitors. Consistent with this view, many cyclic diterpenoid compounds isolated from higher plants have been shown to be physiologically active. The diterpenoid substances whose metabolism is being considered in this research are examples. ent-Kaurene is the cyclic diterpene precursor of the gibberellin family of natural plant growth regulators, while casbene, the momilactones and the oryzalexins are phytoalexins that are thought to be important in the host plant's resistance to microbial pathogens.***//
