Secondary Metabolites as Plant Traits: Current Assessment and Future Perspectives

Referee: Dr. Peter B. Kaufman, Dept. of Biology, University of Michigan, Ann Arbor, MI 48109-1048 Traditionally, secondary metabolites in plants have been investigated by phytochemists. Originally classified as waste products, these compounds more recently have been investigated extensively by ecologists and pharmacologists, and many complex biological functions have been discovered. Secondary metabolites occur nearly in all living organisms, within bacteria as well as in mammals, and are especially prominent in those organisms lacking an immune system. Functions of plant secondary metabolites comprise attractants, such as color pigments and scents, repellents such as antifeedants against insects and mammals, or toxins that affect growth and development of animal and microbial predators. Conversely, insects can employ plant-synthesized compounds to their own advantage, such as signals for feeding and oviposition and location of prey. Microbes also use secondary metabolites as carbon sources, and bacteria utilize them for quorum-sensing, an aspect recently discovered. Despite the diversity of recognized functions, the biochemical processes underlying these interactions are few. Primarily, they relate to the ability of these small molecules to bind to receptor regions of various proteins such as keys into locks. This review attempts a summary of current knowledge of secondary plant metabolism with focus on history of discovery, development of analytical techniques, theories of origin and function, signal pathways, biosynthesis, and assessment of biological activities. Outlined is current utilization by, and future perspectives in, different disciplines, such as chemosystematics, chemical ecology, and agricultural biotechnology. Examples illustrate the strong potential of research in secondary metabolism, particularly in comparison to more established disciplines such as developmental biology and physiology.