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Dissection of the network of indolic defence compounds in Arabidopsis thaliana by multiple mutant analysis

Müller, Teresa M., Böttcher, Christoph, Glawischnig, Erich
Phytochemistry 2019 v.161 pp. 11-20
4-pyridoxic acid, Arabidopsis thaliana, aldehyde oxidoreductases, aldehydes, biosynthesis, cytochrome P-450, genes, genotype, glucosinolates, leaves, metabolites, mutants, phenotype, pyridoxine, ultraviolet radiation
Characteristic for cruciferous plants is the synthesis of a complex array of defence-related indolic compounds. In Arabidopsis, these include indol-3-ylmethyl glucosinolates (IMGs), as well as stress-inducible indole-3-carbaldehyde (ICHO)/indole-3-carboxylic acid (ICOOH) derivatives and camalexin. Key enzymes in the biosynthesis of the inducible metabolites are the cytochrome P450 enzymes CYP71A12, CYP71A13 and CYP71B6 and Arabidopsis Aldehyde Oxidase 1 (AAO1). Multiple mutants in the corresponding genes were generated and their metabolic phenotypes were comprehensively analysed in untreated, UV exposed and silver nitrate-treated leaves. Most strikingly, ICOOH and ICHO derivatives synthesized in response to UV exposure were not metabolically related. While ICHO concentrations correlated with IMGs, ICOOH derivatives were anti-correlated with IMGs and partially dependent on CYP71B6. The AAO1 genotype was shown to not only be important for ICHO metabolism but also for the accumulation of 4-pyridoxic acid, suggesting a dual role of AAO1 in vitamin B6 metabolism and IMG degradation in Arabidopsis.