Müller A, Hillebrand H, Weiler E W
Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität, Bochum, Germany.
Planta. 1998 Oct;206(3):362-9. doi: 10.1007/s004250050411.
The promoter of the nit1 gene, encoding the predominantly expressed isoform of the Arabidopsis thaliana (L.) Heynh. nitrilase isoenzyme family, fused to the beta-glucuronidase gene (uidA) drives beta-glucuronidase expression in the root system of transgenic A. thaliana and tobacco plants. This expression pattern was shown to be controlled developmentally, suggesting that the early differentiation zone of root tips and the tissue surrounding the zone of lateral root primordia formation may constitute sites of auxin biosynthesis in plants. The root system of A. thaliana was shown to express functional nitrilase enzyme. When sterile roots were fed [2H]5-L-tryptophan, they converted this precursor to [2H]5-indole-3-acetonitrile and [2H]5-indole-3-acetic acid. This latter metabolite was further metabolized into base-labile conjugates which were the predominant form of [2H]5-indole-3-acetic acid extracted from roots. When [1-13C]-indole-3-acetonitrile was fed to sterile roots, it was converted to [1-13C]-indole-3-acetic acid which was further converted to conjugates. The results prove that the A. thaliana root system is an autonomous site of indole-3-acetic acid biosynthesis from L-tryptophan.
编码拟南芥（Arabidopsis thaliana (L.) Heynh.）腈水解酶同工酶家族中主要表达异构体的nit1基因的启动子，与β-葡萄糖醛酸酶基因（uidA）融合后，驱动转基因拟南芥和烟草植株根系中β-葡萄糖醛酸酶的表达。这种表达模式显示受发育调控，表明根尖的早期分化区和侧根原基形成区周围的组织可能构成植物生长素生物合成的位点。研究表明拟南芥的根系表达有功能的腈水解酶。当无菌根被饲喂[2H]5-L-色氨酸时，它们将这种前体转化为[2H]5-吲哚-3-乙腈和[2H]5-吲哚-3-乙酸。后一种代谢产物进一步代谢为对碱不稳定的共轭物，这是从根中提取的[2H]5-吲哚-3-乙酸的主要形式。当将[1-13C]-吲哚-3-乙腈饲喂给无菌根时，它被转化为[1-13C]-吲哚-3-乙酸，后者进一步转化为共轭物。结果证明拟南芥根系是从L-色氨酸生物合成吲哚-3-乙酸的自主位点。
