Biosynthesis of Terpenoids By Plants

Terpenoids are a class of chemicals with over 50,000 individual compounds, highly diverse in chemical structure, founded in all kingdoms of life, and are the largest group of secondary plant metabolites. Also known as isoprenoids, their structure began to be elucidated between the 1940s and 1960s, when their basic isoprenoid building blocks were characterized. They play several basic and specialized physiological functions in plants through direct and indirect interactions. Terpenoids are essential to metabolic processes, including post-translational protein modifications, photosynthesis, and intracellular signaling. All terpenoids are built through C5 units condensed to prenyl diphosphate intermediates. The fusion of these C5 units generates short C15-C25, medium C30-C35, and long-chain C40-Cn terpenoids. Along with the extension of the chain, the introduction of functional groups, such as ketones, alcohol, esters and, ethers, forms the precursors to hormones, sterols, carotenoids, and ubiquinone synthesis. The biosynthesis of terpenoids is regulated by spatial, temporal, transcriptional, and post-transcriptional factors. This chapter gives an overview of terpenoid biosynthesis, focusing on both cytoplasmic and plastid pathways, and highlights recent advances in the regulation of its metabolic pathways.