ABA Biosynthetic and Catabolic Pathways - Abscisic Acid: Metabolism, Transport and Signaling - page 21

Chapter 2
ABA Biosynthetic and Catabolic Pathways

Akira Endo, Masanori Okamoto and Tomokazu Koshiba

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 catab-
olism 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 bio-
chemical, 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 bio-
synthesis and catabolism are introduced. These inhibitors can be used to manipulate
endogenous ABA levels and are useful tools to investigate ABA action in plants.

Keywords ABA · Biosynthesis · Catabolism