Altering expression of cinnamic acid 4-hydroxylase in transgenic plants provides evidence for a feedback loop at the entry point into the phenylpropanoid pathway
Altering expression of cinnamic acid 4-hydroxylase in transgenic plants provides evidence for a feedback loop at the entry point into the phenylpropanoid pathway
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DOI：
10.1104/pp.122.1.107
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发表时间：
2000-01-01
期刊：
影响因子：
7.4
通讯作者：
Dixon, RA
中科院分区：
文献类型：
--
作者：
Blount, JW;Korth, KL;Dixon, RA
药理学证据表明，反式肉桂酸是类苯丙烷途径中第一种酶L-苯丙氨酸解氨酶（PAL）的表达和酶活性的反馈调节剂。为了测试这一假设独立的方法，利用潜在的非特异性抑制剂，我们产生了转基因烟草株系的第二种酶的途径，肉桂酸C-羟化酶（C4 H），通过正义或反义表达的苜蓿C4 H cDNA的活性水平改变。PAL活性和苯丙素类化合物的水平降低的植物，其中C4 H活性已被遗传下调的叶和茎。然而，C4 H活性并没有减少在植物中，PAL活性已下调基因沉默。在来自菜豆PAL转基因的过表达PAL的烟草品系和C4 H反义品系之间的杂交中，携带菜豆PAL正义和C4 H反义转基因的后代群体比仅携带PAL转基因的后代群体具有显著更低的可提取的PAL活性。我们的数据提供了一个反馈回路的遗传证据，在进入苯丙烷途径，以前推断从潜在的人工药理学实验的入口点。
Pharmacological evidence implicates trans-cinnamic acid as a feedback modulator of the expression and enzymatic activity of the first enzyme in the phenylpropanoid pathway, L-phenylalanine ammonia-lyase (PAL). To test this hypothesis independently of methods that utilize potentially non-specific inhibitors, we generated transgenic tobacco lines with altered activity levels of the second enzyme of the pathway, cinnamic acid C-hydroxylase (C4H), by sense or antisense expression of an alfalfa C4H cDNA. PAL activity and levels of phenylpropanoid compounds were reduced in leaves and stems of plants in which C4H activity had been genetically down-regulated. However, C4H activity was not reduced in plants in which PAL activity had been down-regulated by gene silencing. In crosses between a tobacco line over-expressing PAL from a bean PAL transgene and a C4H antisense line, progeny populations harboring both the bean PAL sense and C4H antisense transgenes had significantly tower extractable PAL activity than progeny populations harboring the PAL transgene alone. Our data provide genetic evidence for a feedback loop at the entry point into the phenylpropanoid pathway that had previously been inferred from potentially artifactual pharmacological experiments.