Journal Article

Arabidopsis CYP707As Encode (+)-Abscisic Acid 8′-Hydroxylase, a Key Enzyme in the Oxidative Catabolism of Abscisic Acid

Shigeki Saito, Daisaku Ohta, Ohigashi, Hajime, Nobuhiro Hirai, Kanzo Sakata, Masaharu Mizutani, Chiaki Matsumoto

2004

Overview

Abscisic acid (ABA) is involved in a number of critical processes in normal growth and development as well as in adaptive responses to environmental stresses. For correct and accurate actions, a physiologically active ABA level is controlled through fine-tuning of de novo biosynthesis and catabolism. The hydroxylation at the 8′-position of ABA is known as the key step of ABA catabolism, and this reaction is catalyzed by ABA 8′-hydroxylase, a cytochrome P450. Here, we demonstrate CYP707As as the P450 responsible for the 8′-hydroxylation of (+)-ABA. First, all four CYP707A cDNAs were cloned from Arabidopsis and used for the production of the recombinant proteins in insect cells using a baculovirus system. The insect cells expressing CYP707A3 efficiently metabolized (+)-ABA to yield phaseic acid, the isomerized form of 8′-hydroxy-ABA. The microsomes from the insect cells exhibited very strong activity of 8′-hydroxylation of (+)-ABA (Km = 1.3 μM and kcat = 15 min-1). The solubilized CYP707A3 protein bound (+)-ABA with the binding constant $K_{\\text{s}}$ = 3.5 μM, but did not bind (-)-ABA. Detailed analyses of the reaction products confirmed that CYP707A3 does not have the isomerization activity of 8′-hydroxy-ABA to phaseic acid. Further experiments revealed that Arabidopsis CYP707A1 and CYP707A4 also encode ABA 8′-hydroxylase. The transcripts of the CYP707A genes increased in response to salt, osmotic, and dehydration stresses as well as ABA. These results establish that the CYP707A family plays a key role in regulating the ABA level through the 8′-hydroxylation of (+)-ABA.

• Publisher: American Society of Plant Biologists
• Subject: abscisic acid / Abscisic Acid - metabolism / Abscisic Acid - pharmacology / Animals / Arabidopsis / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis Proteins / Arabidopsis Proteins - genetics / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / Binding Sites / Binding Sites - drug effects / Binding Sites - genetics / biochemical pathways / Biochemical Processes and Macromolecular Structures / Biosynthesis / Brassinosteroids / Catabolism / chemistry / Cholestanols / Cholestanols - pharmacology / Cloning, Molecular / Complementary DNA / Cultured cells / cytochrome P-450 / Cytochrome P-450 Enzyme System / Cytochrome P-450 Enzyme System - genetics / Cytochrome P-450 Enzyme System - metabolism / Cytochromes / DNA, Complementary / DNA, Complementary - chemistry / DNA, Complementary - genetics / drug effects / enzyme activity / enzyme substrates / Enzymes / enzymology / gene expression regulation / Gene Expression Regulation, Enzymologic / Gene Expression Regulation, Enzymologic - drug effects / Gene Expression Regulation, Plant / Gene Expression Regulation, Plant - drug effects / Genes / genetics / gibberellic acid / Gibberellins / Gibberellins - pharmacology / hydroxylation / Insect viruses / Insecta / Insecta - genetics / Insecta - metabolism / Isoenzymes / Isoenzymes - genetics / Isoenzymes - metabolism / Isomerization / metabolism / Microsomes / Microsomes - enzymology / Mixed Function Oxygenases / Mixed Function Oxygenases - genetics / Mixed Function Oxygenases - metabolism / Molecular Sequence Data / Multigene Family / nucleotide sequences / oxidation / Oxidation-Reduction / Oxidation-Reduction - drug effects / oxygenases / pharmacology / Phylogeny / Plant Growth Regulators / Plant Growth Regulators - pharmacology / plant proteins / Protein Binding / Protein Binding - drug effects / Protein Binding - genetics / recombinant fusion proteins / salt stress / Spodoptera frugiperda / Steroids, Heterocyclic / Steroids, Heterocyclic - pharmacology / tissue distribution / water stress