N. crassa produces IAA and other related indolic compounds when supplemented with tryptophan. (A) TLC analysis to find the lowest concentration of tryptophan that can be used by N. crassa to produce IAA. White arrows in lane 1 and 2 indicate traces of IAA. Different tryptophan concentrations were used in lane 1 (5 μM), 2 (1 μM), 3 (100 nM), 4 (50 nM), 5 (25 nM), and 6 (without tryptophan). (B) HPLC analysis of the metabolites produced by wild type N. crassa with and without tryptophan supplementation for 72 hours. (C) Metabolite profiling of wild type as well as single knock-out N. crassa strains using HPLC. Single knock-outs for the genes specifically present in the IPA pathway of IAA biosynthesis were used. The following standards were used: tryptophan (Trp), indole-3-lactic acid (ILA), indole-3-acetic acid (IAA), tryptophol (TOL) and indole-3-acetonitrile (IAN).