Regulation and manipulation of ABA biosynthesis in roots
Regulation and manipulation of ABA biosynthesis in roots
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DOI：
10.1111/j.1365-3040.2006.01606.x
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发表时间：
2007-01-01
影响因子：
7.3
通讯作者：
Taylor, Ian B.
中科院分区：
文献类型：
--
作者：
Thompson, Andrew J.;Mulholland, Barry J.;Taylor, Ian B.
已知9-顺式环氧类胡萝卜素双加氧酶（NCED）的过表达导致叶片、种子和整株植物中脱落酸（阿坝）的积累。在这里，我们调查了阿坝生物合成的操纵根。组成型过表达LeNCED 1的整个番茄植株的根具有比野生型（WT）根更高的阿坝含量。这可以解释为增强原位阿坝的生物合成，而不是进口的阿坝从地上部，因为根培养物也有较高的阿坝含量，因为四环素（Tc）诱导的LeNCED 1的表达引起阿坝积累在孤立的烟草根。然而，Tc诱导的表达导致叶片中阿坝的积累大于根。这表明第一次，NCED是限速的根组织，但表明，其他步骤也限制了途径通量，更多的是在根比叶。脱水和NCED过表达协同作用，提高番茄根培养中阿坝的积累。一种解释是，叶黄素合成增加根脱水，并在支持这一点，脱水处理增加β-胡萝卜素羟化酶mRNA水平。整株过表达LeNCED 1表现出大大降低气孔导度和嫁接实验从这项研究表明，这主要是由于阿坝合成增加，而不是在根中的叶子。叶黄素供应和环氧类胡萝卜素裂解的遗传操作可能需要加强根阿坝的生物合成足以在拍摄信号气孔关闭。
Overexpression of 9-cis-epoxycarotenoid dioxygenase (NCED) is known to cause abscisic acid (ABA) accumulation in leaves, seeds and whole plants. Here we investigated the manipulation of ABA biosynthesis in roots. Roots from whole tomato plants that constitutively overexpress LeNCED1 had a higher ABA content than wild-type (WT) roots. This could be explained by enhanced in situ ABA biosynthesis, rather than import of ABA from the shoot, because root cultures also had higher ABA content, and because tetracycline (Tc)-induced LeNCED1 expression caused ABA accumulation in isolated tobacco roots. However, the Tc-induced expression led to greater accumulation of ABA in leaves than in roots. This demonstrates for the first time that NCED is rate-limiting in root tissues, but suggests that other steps were also restrictive to pathway flux, more so in roots than in leaves. Dehydration and NCED overexpression acted synergistically in enhancing ABA accumulation in tomato root cultures. One explanation is that xanthophyll synthesis was increased during root dehydration, and, in support of this, dehydration treatments increased beta-carotene hydroxylase mRNA levels. Whole plants overexpressing LeNCED1 exhibited greatly reduced stomatal conductance and grafting experiments from this study demonstrated that this was predominantly due to increased ABA biosynthesis in leaves rather than in roots. Genetic manipulation of both xanthophyll supply and epoxycarotenoid cleavage may be needed to enhance root ABA biosynthesis sufficiently to signal stomatal closure in the shoot.