Plant photomorphogenesis is a complex developmental process under the control of at least three distinct photoreceptors and involving differential gene expression in both nuclear and organellar genomes. During this process a characteristic "greeting" of place. We are interested in understanding the biochemical and molecular genetic control of chlorophyll formation in higher plants. We have identified cDNAs and/or cloned genomic sequences encoding three enzymes of the chlorophyll biosynthetic pathway. These enzymes participate in this pathway either as regulatory (e.g., NADPH- protochlorophyllide oxidoreductase (PCR) or non-rate-limiting steps (e.g., ALA-dehydratase (ALAD), PBG deaminase (PBGD) and are thought to be under phytochrome-mediated photoregulation either in a positive manner (ALAD), a negative manner (PCR), or to be unaffected by light (PBGD). We propose to continue our characterization of the structure, complexity, and organization of the gene families that encode these three chloroplast proteins. The expression characteristics of the individual family members will be analyzed with respect to light, extent of plastid differentiation and cell type. Since substantial evidence supporting the presence of a dual pathway for tetrapyrrole formation in higher plants exists, we will determine whether individual members of these gene families give rise to proteins localized in different subcellular compartments (chloroplastic versus cytosolic) and if so, whether members of a gene family giving rise to proteins compartmentalized in different subcellular locations are under different regulatory programs. Green plants produce chlorophyll both in response to light in their environment, and as part of their own normal developmental processes. The control of chlorophyll biosynthesis is complex, but poorly understood. This is a proposal to elucidate that control.***
