Transport of Indole-3-Butyric Acid and Indole-3-Acetic Acid in Arabidopsis Hypocotyls Using Stable Isotope Labeling
Transport of Indole-3-Butyric Acid and Indole-3-Acetic Acid in Arabidopsis Hypocotyls Using Stable Isotope Labeling
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DOI：
10.1104/pp.111.191288
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发表时间：
2012-04-01
期刊：
影响因子：
7.4
通讯作者：
Cohen, Jerry D.
中科院分区：
文献类型：
--
作者：
Liu, Xing;Barkawi, Lana;Cohen, Jerry D.
利用放射性示踪技术研究了天然生长素吲哚丁酸（IBA）和吲哚乙酸（IAA）在拟南芥下胚轴中的极性运输。由于单独的放射性测定不能区分IBA及其代谢物，因此检测到的来自应用的[H-3] IBA的转运可能是由IBA代谢物（包括IAA）的转运引起的。为了验证这一假设，我们使用基于质谱的方法通过跟踪[C-13（1）] IBA和来源于[C-13（1）]IBA的[C-13（1）]IAA的运动来定量IBA在拟南芥下胚轴中的运输。我们还在平行对照实验中测定了[C-13（6）]IAA的转运。结果表明，[C-13（1）]IBA的运输量明显低于[C-13（6）]IAA，且生长素运输抑制剂N-1-naphthalamic acid对IBA的运输无明显影响。大量的[C-13（1）]IBA在运输过程中转化为[C-13（1）]IAA，但[C-13（1）]IBA的运输不依赖于IBA转化为IAA。在下胚轴顶端，[C-13（1）]IBA大部分转化为酯键[C-13（1）]IBA，基端酯键[C-13（1）]IBA的含量高于游离[C-13（1）]IBA。相反，下胚轴顶端的[C-13（6）]IAA大部分转化为酰胺连接的[C-13（6）]IAA，而基端的共轭[C-13（6）]IAA很少。结果表明，IBA在拟南芥下胚轴中的极性运输远低于IAA，其运输机制与IAA不同。这些实验还建立了一种使用稳定同位素标记来定量植物中小分子运动的方法。
The polar transport of the natural auxins indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA) has been described in Arabidopsis (Arabidopsis thaliana) hypocotyls using radioactive tracers. Because radioactive assays alone cannot distinguish IBA from its metabolites, the detected transport from applied [H-3] IBA may have resulted from the transport of IBA metabolites, including IAA. To test this hypothesis, we used a mass spectrometry-based method to quantify the transport of IBA in Arabidopsis hypocotyls by following the movement of [C-13(1)] IBA and the [C-13(1)]IAA derived from [C-13(1)]IBA. We also assayed [C-13(6)]IAA transport in a parallel control experiment. We found that the amount of transported [C-13(1)]IBA was dramatically lower than [C-13(6)]IAA, and the IBA transport was not reduced by the auxin transport inhibitor N-1-naphthylphthalamic acid. Significant amounts of the applied [C-13(1)]IBA were converted to [C-13(1)]IAA during transport, but [C-13(1)]IBA transport was independent of IBA-to-IAA conversion. We also found that most of the [C-13(1)]IBA was converted to ester-linked [C-13(1)]IBA at the apical end of hypocotyls, and ester-linked [C-13(1)]IBA was also found in the basal end at a level higher than free [C-13(1)]IBA. In contrast, most of the [C-13(6)]IAA was converted to amide-linked [C-13(6)]IAA at the apical end of hypocotyls, but very little conjugated [C-13(6)]IAA was found in the basal end. Our results demonstrate that the polar transport of IBA is much lower than IAA in Arabidopsis hypocotyls, and the transport mechanism is distinct from IAA transport. These experiments also establish a method for quantifying the movement of small molecules in plants using stable isotope labeling.