Grant: Discovery Grants Program - Individual

Higher plants are remarkable organisms for their ability to generate highly complex and biologically innovative biochemistry that is responsible for the biosynthesis and accumulation of diverse pigments, aromas and biologically active organic molecules. while most molecules are not directly essential for survival many play key roles in plant adaptation to the biotic and abiotic environment. The unique biological activities of this chemical diversity have provided medicinal and disease preventing molecules that have been used by humanity to prevent/cure many devastating diseases. The monoterpenoid indole alkaloids (MIAs) make up the largest and most diverse class of compounds that are characteristically found within many members of the Apocynaceae (4700 species), the Loganiaceae (600 species) and the Rubiaceae (>10,000 species) plant families. The complexity of MIA chemistry is matched by their remarkably diverse biological activity on living organisms and that has led to their use as drugs for preventing malaria (quinine), for treating neurological disorders (reserpine, cancer (camptothecin, vincristine, vinblastine), as a vasodilator and as potential analgesics and novel pain killers (conolidine and akuammicine) in human beings. Over the past 30 years my research group has made numerous discoveries about MIA biosynthesis in the Madagascar periwinkle (Catharanthus roseus) that has recently culminated in our recent functional characterization and elucidation of 10 genes and their biochemical roles in the formation of Catharanthus anticancer MIAs (vinblastine and vincristine that have bee used in chemotherapy treatments over the past 45 years. These discoveries have revealed numerous biologically active intermediates that fuel alternative MIA pathways responsible for their diversity in Nature. Present studies will use virus induced gene silencing of target genes to probe how MIA intermediates may alter overall gene expression in affected tissues. In some cases, accumulation of the intermediate is likely to activate alternative MIA pathways that were silent or if the MIA is toxic, the primary stress responses may be activated and will be studied. The results obtained will be used in the discovery of new MIA pathway genes and in identifying biological activities of the MIA intermediates in the affected tissues. A separate project will continue the identification of mutants for MIA biosynthesis from a C. roseus population treated with ethyl methanesulphonate mutagen. This approach has already proven successful in the previous grant cycle and it will provide new insights into the biological properties of MIA intermediates and of the biochemical pathway involved while making the intermediate reproducibly available in reasonable quantities by extraction from the mutant plant.