75.IAAの酸化および抱合体化に関する植物種間差(口頭発表)

概要

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Endogenous level of indole-3-acetic acid (IAA) (1) is strictly controlled by multiple mechanisms, of which metabolism represents one of key factors. To date, many metabolites of IAA have been identified in various plants, but the whole picture of IAA metabolic pathways, or metabolite profile in each plant has not been well investigated. We conducted a comparative study of IAA metabolite profile using Arabidopsis and several gramineous plants including rice, wheat and maize, in order to demonstrate the diversity of IAA metabolism among plants. Plant seedlings were homogenized in liquid N_2 and extracted with 80% acetone. The extracts were purified with solid phase C18 cartridges, and free IAA and its metabolites were quantified by LC-ESI-MS/MS operated in the MRM mode. The obtained quantitative metabolite profiles depended on the tested plants, characteristic major metabolites being OxIAA-Glc (7), amino acid conjugates of IAA-N-Glc (3) (5), and 7-O-Glc-OxIAA (9) in Arabidopsis, rice and maize respectively. No known compounds were detected as major metabolites for the case of wheat. Independently of the plant species, exogenous IAA was mainly metabolized into IAA-Asp (2) and/or IAA-Glu (4). Further search for unknown IAA metabolites using LC-ESI-MS/MS led to detection of DiOxIAA (10), the level of which was considerably high in rice. Thus, one of the major catabolic routes in rice is proposed as follows: IAA (1)→OxIAA (6)→DiOxIAA (10).
2008-10-06