Chapter seven Multiple levels of control in the regulation of alkaloid biosynthesis

Abstract

Summary Alkaloid biosynthetic pathways are under strict regulation in plants. Until now, our limited knowledge of the fundamental mechanisms involved in the control of alkaloid metabolism has severely restricted our ability to harness the vast biotechnological potential of these important secondary pathways. For example, the use of plant cell cultures for the commercial production of pharmaceutical alkaloids has not become a reality despite decades of empirical research. The application of traditional and modern biochemical, molecular, and cellular techniques has revealed important clues about the reasons why C. roseus cultures accumulate tabersonine and catharanthine, but not vindoline or vinblastine, and why opium poppy cultures produce sanguinarine, but not codeine or morphine. The inability of dedifferentiated cells to accumulate certain metabolites was interpreted as evidence that the operation of many alkaloid pathways is tightly coupled to the development of specific tissues. Recent studies have shown that alkaloid pathways are regulated at multiple levels, including cell type-specific gene expression, induction by light and elicitors, enzymatic controls, and other poorly understood metabolic mechanisms. Our ability to exploit the biosynthetic capacity of plants through, for example, metabolic engineering will require a thorough understanding of the mechanisms that allow a cell to produce specific alkaloids. Advances in genomics will provide a more rapid and efficient means to identify new biosynthetic and regulatory genes involved in alkaloid pathways. The apparently unique aspects of alkaloid biosynthesis also provide intriguing targets for plant cell biology research, in general. Novel insights obtained using a combination of traditional and modern technologies, including biochemistry, molecular biology, cell biology, and genetic engineering, highlight the importance of a multifaceted approach in studying the regulation of alkaloid biosynthesis in plants.