The aims of this research are to isolate and characterize intact cDNAs and genes coding for trans- cinnamic acid hydroxylase in pea seedlings; to characterize, at the nucleotide level, the isolated gene(s) and the adjacent regulatory regions through cloning and complete sequence analysis; and to characterize the immunological level of the plant microsomal P-450s.%%% The broad, overall goal of the proposed research is to elucidate the molecular mechanisms for the regulation and control of gene expression in plant tissue, focusing the near term objectives on the cytochrome P-450 monoxygenase systems found ubiquitously in the plant kingdom. These enzymes play paramount roles in the detoxification of plant xenobiotics, in the biosynthesis of plant hormones, and in the production of key intermediates in the synthesis of lignins, terpenes, flavonoids and phenolic acids. The de novo synthesis of some cytochrome P-450 monoxygenases appear to be regulated by light and by the administration of a variety of synthetic auxins and herbicides. Control over the P-450 mediated metabolism of these compounds could lead to physiologically relevant herbicide resistance and plant hormone regulation events. Many general features of the regulatory processes elucidated through these studies will have general application to other mechanistic questions in plant gene expression.***//