Chlorinated Auxins-How Does Arabidopsis Thaliana Deal with Them?

• Published in: International journal of molecular sciences 2020-04, Vol.21 (7), p.2567
• Main Authors: Walter, Antje, Caputi, Lorenzo, O'Connor, Sarah, van Pée, Karl-Heinz, Ludwig-Müller, Jutta
• Format: Article
• Language: English
• Subjects: Acetic acid; Acetonitrile; Amino acids; Amino Acids - metabolism; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; auxin; Auxins; Bacteria; bacterial halogenase; Biological activity; chloro-tryptophan, chloro-indole acetic acid, chloro-indole acetonitrile, plant natural products, plant metabolic engineering; Conjugates; Enzymes; Fabaceae - metabolism; Flavin; Flowers & plants; Fungi; Gene Expression Regulation, Plant - physiology; Halogenation; Halogenation - physiology; Hormones; Indoleacetic acid; Indoleacetic Acids - metabolism; Indoles - metabolism; Legumes; Leguminous plants; Metabolic pathways; Phenotypes; Pisum sativum - metabolism; Plant growth; Plant Growth Regulators - metabolism; Plant Roots - metabolism; Seeds; Transgenic plants; Tryptophan; Tryptophan - metabolism
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21072567

Plant hormones have various functions in plants and play crucial roles in all developmental and differentiation stages. Auxins constitute one of the most important groups with the major representative indole-3-acetic acid (IAA). A halogenated derivate of IAA, 4-chloro-indole-3-acetic acid (4-Cl-IAA), has previously been identified in and other legumes. While the enzymes responsible for the halogenation of compounds in bacteria and fungi are well studied, the metabolic pathways leading to the production of 4-Cl-IAA in plants, especially the halogenating reaction, are still unknown. Therefore, bacterial flavin-dependent tryptophan-halogenase genes were transformed into the model organism . The type of chlorinated indole derivatives that could be expected was determined by incubating wild type with different Cl-tryptophan derivatives. We showed that, in addition to chlorinated IAA, chlorinated IAA conjugates were synthesized. Concomitantly, we found that an auxin conjugate synthetase (GH3.3 protein) from was able to convert chlorinated IAAs to amino acid conjugates in vitro. In addition, we showed that the production of halogenated tryptophan (Trp), indole-3-acetonitrile (IAN) and IAA is possible in transgenic in planta with the help of the bacterial halogenating enzymes. Furthermore, it was investigated if there is an effect (i) of exogenously applied Cl-IAA and Cl-Trp and (ii) of endogenously chlorinated substances on the growth phenotype of the plants.