Gloria Coruzzi
Robert Last

In addition to their obvious role in protein synthesis (see Chapter 9), amino acids perform essential functions in both primary and secondary plant metabolism. Some amino acids serve to assimilate nitrogen and transport it from sources to sinks; others serve as precursors to secondary products such as hormones and compounds involved in plant defense. Thus, the synthesis of amino acids directly or indirectly controls various aspects of plant growth and development. Recent investigations of genes involved in amino acid biosynthesis reveal that this is a dynamic process controlled by metabolic, environmental, and developmental factors. This chapter will highlight examples in which combined molecular, biochemical, and genetic approaches have helped define the pathways and uncover regulatory mechanisms of amino acid biosynthesis in plants. These studies have implications for both basic and applied research because amino acid biosynthesis genes are targets for herbicide action and metabolic engineering of transgenic crop plants. A comprehensive review of the biochemistry of amino acid synthesis can be found elsewhere (see Further Reading).