Plant natural products include a diverse array of compounds that play important roles in plant metabolism and physiology. After elucidation of biosynthetic pathways and regulatory factors, it has become possible to metabolically engineer new capabilities in planta as well as successfully engineer whole pathways into microbial systems. Microbial expression systems for producing valuable plant compounds have evolved to incorporate polyculture and co-culture consortiums for carrying out robust biosynthesis strategies. This review focuses on four classes of plant secondary metabolites and the recent advances in generating useful compounds in microbial expression platforms and in plant metabolic engineering. They are the flavonoids, alkaloids, betalains, and glucosinolates
