Present study investigated the regulation and production of phytohormone indole-3-acetic acid (IAA) and other indole derivatives by the fungus Colletotrichum acutatum. Using HPLC and chromogenic stains after fluorescence thin-layer chromatography, biosynthesis of IAA and other indoles, including indole-acetaldehyde (IAAld), indole-acetamide (IAM), indole-lactic acid (ILA), indole-pyruvic acid (IPA) and tryptophol (TOL) were solely dependent on the presence of tryptophan (Trp) and were highly regulated by carbon and nitrogen sources by C. acutatum. As compared to other sources, the production of IAA increased drastically (up to 12-fold) using mannitol or galactose as the sole carbon source, or using ammonium nitrate as the sole nitrogen source, whereas IAA was completely suppressed in the presence of ammonium chloride. The putative pathways for IAA biosynthesis by C. acutatum likely proceeded via Trp/IPA/IAAld and Trp/IAM intermediates. This study provides an opportunity to identify genes involved in IAA biosynthesis by using suppression subtractive hybridization approach and provides a nutrient base for screening IAA non-producing mutants of C. acutatum.
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Turksen Shilts, Umran Erturk, Nickash J. Patel and Kuang-Ren Chung, 2005. Physiological Regulation of Biosynthesis of Phytohormone Indole-3-acetic Acid and Other Indole Derivatives by the Citrus Fungal Pathogen Colletotrichum acutatum. Journal of Biological Sciences, 5: 205-210.