Metabolism of indole-3-acetic acid in rice: identification and characterization of N-beta-D-glucopyranosyl indole-3-acetic acid and its conjugates.
A search was made for conjugates of indole-3-acetic acid (IAA) in rice (Oryza sativa) using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) in order to elucidate unknown metabolic pathways for IAA. N-beta-d-Glucopyranosyl indole-3-acetic acid (IAA-N-Glc) was found in an alkaline hydrolysate of rice extract. A quantitative analysis of 3-week-old rice demonstrated that the total amount of IAA-N-Glc was equal to that of IAA. A LC-ESI-MS/MS-based analysis established that the major part of IAA-N-Glc was present as bound forms with aspartate and glutamate. Their levels were in good agreement with the total amount of IAA-N-Glc during the vegetative growth of rice. Further detailed analysis showed that both conjugates highly accumulated in the root. The free form of IAA-N-Glc accounted for 60% of the total in seeds but could not be detected in the vegetative tissue. An incorporation study using deuterium-labeled compounds showed that the amino acid conjugates of IAA-N-Glc were biosynthesized from IAA-amino acids. IAA-N-Glc and/or its conjugates were also found in extracts of Arabidopsis, Lotus japonicus, and maize, suggesting that N-glucosylation of indole can be the common metabolic pathway of IAA in plants.
Kai
Kenji
K
Division of Applied Life Science, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Wakasa
Kyo
K
Miyagawa
Hisashi
H
D000577:Amides / Q000378:metabolism; D001224:Aspartic Acid / Q000378:metabolism; D002853:Chromatography, Liquid; D018698:Glutamic Acid / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D007211:Indoles / Q000138:chemical synthesis / Q000302:isolation & purification; D009005:Monosaccharides / Q000096:biosynthesis / Q000138:chemical synthesis / Q000302:isolation & purification; D012275:Oryza / Q000254:growth & development / Q000378:metabolism*; D010936:Plant Extracts / Q000737:chemistry; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
D000577:Amides; D007210:Indoleacetic Acids; D007211:Indoles; D009005:Monosaccharides; C525890:N-beta-D-glucopyranosyl indole-3-acetic acid; D010936:Plant Extracts; D001224:Aspartic Acid; D018698:Glutamic Acid; C030737:indoleacetic acid