ABA Biosynthetic and Catabolic Pathways

© Springer Science+Business Media Dordrecht 2014 D.-P. Zhang (ed.), Abscisic Acid: Metabolism, Transport and Signaling, DOI 10.1007/978-94-017-9424-4_2 Abstract Abscisic acid (ABA) is a phytohormone that regulates physiological processes such as seed maturation, seed dormancy, and stress adaptation. These physiological responses are triggered by the fluctuation of endogenous ABA levels in accordance with changing surroundings or developmental stimuli. Endogenous ABA levels are largely controlled by the balance between biosynthesis and catabolism. ABA is also synthesized in various kinds of organisms other than plants. To manipulate ABA levels, we first need to understand the pathways for ABA biosynthesis and catabolism in each organism. The biosynthetic pathway has been extensively studied in plants and phytopathogenic fungi. The catabolic pathway has been mostly established in plants. Extensive investigations of mutants defective in ABA metabolism using biochemical, molecular genetic, and genomic approaches have helped to reveal the main framework of these pathways. This chapter reviews our current understanding of the pathways of ABA biosynthesis and catabolism. In addition, inhibitors of ABA biosynthesis and catabolism are introduced. These inhibitors can be used to manipulate endogenous ABA levels and are useful tools to investigate ABA action in plants.