Indole-3-acetic acid biosynthetic pathways in the basidiomycetous yeast Rhodosporidium paludigenum
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Microorganisms produce plant growth regulators, such as auxins, cytokinins and gibberellins, to promote plant growth. Auxins are a group of compounds with an indole ring that have a positive effect on plant growth. Indole-3-acetic acid (IAA) is a plant growth hormone classified as an indole derivative of the auxin family. IAA biosynthesis pathways have been reported and widely studied in several groups of bacteria. Only a few studies on IAA biosynthesis pathways have been conducted in yeast. This study aimed to investigate IAA biosynthesis pathways in a basidiomycetous yeast (Rhodosporidium paludigenum DMKU-RP301). Investigations were performed both with and without a tryptophan supplement. Indole compound intermediates were detected by gas chromatography–mass spectrometry. Indole-3-lactic acid and indole-3-ethanol were found as a result of the enzymatic reduction of indole-3-pyruvic acid and indole-3-acetaldehyde, in IAA biosynthesis via an indole-3-pyruvic acid pathway. In addition, we also found indole-3-pyruvic acid in culture supernatants determined by high-performance liquid chromatography. Identification of tryptophan aminotransferase activity supports indole-3-pyruvic acid-routed IAA biosynthesis in R. paludigenum DMKU-RP301. We hence concluded that R. paludigenum DMKU-RP301 produces IAA through an indole-3-pyruvic acid pathway.
KeywordsBasidiomycetous yeast Red yeast Rhodosporidium Indole-3-acetic acid Biosynthetic pathway
This work was supported by a Thailand Research Fund/TRF Research Team Promotion Grant (RTA 548009) under the title “Biodiversity and ecology of endophytic and epiphytic yeasts from leaves of agronomic crops in Thailand and production of plant growth promoting auxins by the selected promising strain with the elucidation of its biosynthetic pathway” and the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission.
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