indole-3-acetonitrile and tryptamine

Fusarium graminearum is a devastating pathogenic fungus causing fusarium head blight (FHB) of wheat. This fungus can produce indole-3-acetic acid (IAA) and a very large amount of IAA accumulates in wheat head tissues during the first few days of infection by F. graminearum. Using liquid culture conditions, we have determined that F. graminearum can use tryptamine (TAM) and indole-3-acetonitrile (IAN) as biosynthetic intermediates to produce IAA. It is the first time that F. graminearum is shown to use the l-tryptophan-dependent TAM and IAN pathways rather than the indole-3-acetamide or indole-3-pyruvic acid pathways to produce IAA. Our experiments also showed that exogenous IAA was metabolized by F. graminearum. Exogenous IAA, TAM, and IAN inhibited mycelial growth; IAA and IAN also affected the hyphae branching pattern and delayed macroconidium germination. IAA and TAM had a small positive effect on the production of the mycotoxin 15-ADON while IAN inhibited its production. Our results showed that IAA and biosynthetic intermediates had a significant effect on F. graminearum physiology and suggested a new area of exploration for fungicidal compounds.

Topics: Biosynthetic Pathways; Fusarium; Indoleacetic Acids; Indoles; Mycelium; Plant Growth Regulators; Spores, Fungal; Trichothecenes; Triticum; Tryptamines; Tryptophan

A simple, quick and reliable method is proposed for the detection and quantitation of indole-3-acetate (IAA) and indole-3-butyrate (IBA), an auxin phytohormone produced by rhizobacteria from l-tryptophan (Trp) metabolism using high performance thin-layer chromatography (HPTLC). Microbial auxin biosynthesis routes involve Trp as a precursor where other than IAA and IBA, products such as indole-3-pyruvate (IPA), indole-3-acetamide (IAM), tryptamine, indole-3-acetonitrile (IAN), indole-3-lactic acid (ILA) and indole-3-acetaldehyde (IAAld) are also produced. In traditional spectrophotometric method, Salkowski reagent develops color by reacting with indolic compounds. The color development is non-specific contributed by several Trp derivatives produced by rhizobacteria rather than IAA only. To overcome this limitation, HPTLC based protocol is developed to precisely detect and quantify IAA and IBA in the range of 100 to 1000ng per spot. This protocol is applicable to detect and quantify IAA and IBA from microbial samples ignoring other Trp derivatives. For microbial samples, the spectrophotometric method gives larger values as compared to HPTLC derived values which may be attributed by total indolic compounds reacting with Salkowski reagent rather than only IAA and/or IBA.

Topics: Bacillus; Chromatography, Thin Layer; Indoleacetic Acids; Indoles; Limit of Detection; Micrococcaceae; Pseudomonas aeruginosa; Rhizobium; Spectrophotometry; Tryptamines; Tryptophan