Summary

Apart from serving as protein building blocks, amino acids play multiple regulatory roles in plant growth, including nitrogen assimilation and transport, carbon/nitrogen balance, production of hormones and secondary metabolites, stress-associated metabolism, and many other processes. Some of the amino acids are of particular importance not only for plant growth but also for the nutritional quality of plant foods and feeds because human and its ruminant and nonruminant livestock cannot synthesize them and depend on their availability in their diets. Genetic and metabolic engineering approaches have contributed tremendously to the understanding of the regulation of amino acid metabolism in plants. This chapter discusses how amino acid metabolism is regulated by complex regulatory networks that operate in concert with other regulatory networks of carbon and likely also lipid metabolism. These networks are, however, also subjected to concerted spatial, temporal, developmental, and environmental controls. The combined application of genomic, proteomic, and metabolomic approaches coupled with genetic and metabolic engineering, as well as analysis of dynamic fluxes in different intracellular organelles, offers a promising future for the dissection of these compound regulatory networks.