13.トウモロコシ幼葉鞘先端におけるindole-3-acetic acid(IAA)合成量を指標としたIAA生合成に影響を与える物質のケミカルスクリーニング(口頭発表)

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The plant hormone auxin (IAA) plays important roles in many plant physiological events. In the study of IAA biosynthesis, genetic approaches have identified several IAA biosynthetic genes, but endogenous IAA levels are not significantly reduced in the proposed IAA biosynthetic mutants. Thus, its biosynthetic pathways remain a mess to sort out. We have previously shown that maize coleoptile tips involve active sites for biosynthesis of IAA from tryptophan. To identify compounds which affect the amount of IAA synthesized in the tip, we carried out an IAA quantification-based screening of chemicals by using HitFinder library (10,000 chemicals). Apical 2-mm region of coleoptiles (4-day-old) were sectioned and incubated for 2hrs in a K^+-phosphate buffer (KPB) with or without chemical. The amounts of IAA diffused into a KPB were measured by HPLC-fluorescent photometer. The levels of IAA were about 800pg/tip/2h in the control (KPB without chemical). After the first screening, we selected out 105 candidates that reduced the amounts of IAA to less than 300pg/tip/2h, and 41 candidates that increased the levels to more than 1400pg/tip/2h. Among those, 43 chemicals significantly reduced the levels of IAA in a dose-dependent manner and one chemical increased the levels of IAA. We are currently investigating the effect of these chemicals on IAA production in maize coleoptile tips.
植物化学調節学会の論文
2009-10-06