Chapter 1 Regulation of Alkaloid Biosynthesis in Plants

Abstract

Publisher Summary This chapter focuses on recent advances in the metabolic regulation involved in the biosynthesis of six groups of alkaloids—benzylisoquinoline (BA), monoterpenoid indole, tropane, purine, pyrrolizidine, and quinolizidine alkaloids for which biosynthetic and regulatory genes have been reported and characterized. BA biosynthesis begins with the conversion of tyrosine into both dopamine and 4–hydroxyphenylacetaldehyde by a lattice of decarboxylations, ortho-hydroxylations, and deaminations. Monoterpenoid indole alkaloids consist of an indole moiety provided by tryptamine and a terpenoid component derived from the iridoid glucoside secologanin. The regulation of alkaloid biosynthesis includes: developmental and environmental controls, signal transduction, promoter elements and transcriptional regulators, metabolic channels and enzyme complexes, and cellular compartmentalization and trafficking. The application of genomics to the study of alkaloid biosynthesis focuses on BA metabolism in opium poppy and C. japonica, monoterpenoid indole alkaloid metabolism in C. roseus, and nicotine metabolism in tobacco. Metabolic engineering is broadly defined as the improvement of cellular activities by the manipulation of enzymatic, transport, or regulatory functions using recombinant DNA technology. Several alkaloid biosynthetic genes have been used to genetically alter the production of various secondary metabolites in plants. Transgenic plants with altered or novel enzyme activities have also become a powerful tool to study the metabolic control architecture of alkaloid pathways.