The Growth Reduction Associated with Repressed Lignin Biosynthesis in Arabidopsis thaliana Is Independent of Flavonoids
The Growth Reduction Associated with Repressed Lignin Biosynthesis in Arabidopsis thaliana Is Independent of Flavonoids
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DOI：
10.1105/tpc.110.074161
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发表时间：
2010-05-01
期刊：
影响因子：
11.6
通讯作者：
Chapple, Clint
中科院分区：
文献类型：
--
作者：
Li, Xu;Bonawitz, Nicholas D.;Chapple, Clint
由羟基肉桂酰CoA：莽草酸羟基肉桂酰转移酶（HCT）或对香豆酰莽草酸3 '-羟化酶（C3' H）缺乏引起的苯丙素类生物合成缺陷导致拟南芥中木质素减少、类黄酮过度积累和生长抑制。以前有报道，类黄酮介导的生长素运输抑制是HCT-RNA干扰（RNAi）植物生长减少的原因。这一结论是基于观察到HCT和查耳酮合酶（CHS）（类黄酮生物合成所必需的酶）的同时RNAi沉默导致比单独HCT沉默更不严重的矮化。在尝试使用C39 H突变体（ref 8）和CHS无效突变体（tt 4 -2）扩展这些结果时，我们发现缺乏类黄酮的ref 8 tt 4 -2双突变体的生长表型与ref 8的生长表型无法区分。此外，使用RNAi，我们发现HCT沉默和生长抑制之间的关系在野生型和tt 4 -2中是相同的。我们从这些结果中得出结论，在HCT-RNAi植物和ref 8突变体中观察到的生长抑制与黄酮类化合物无关。最后，我们表明，一个新的特点绕过HCT和C39 H基因的表达部分恢复了HCT-RNAi植物中的木质素生物合成和生长，表明松柏醛下游的生化途径，可能是木质化，是植物正常生长所必需的。
Defects in phenylpropanoid biosynthesis arising from deficiency in hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HCT) or p-coumaroyl shikimate 3'-hydroxylase (C3'H) lead to reduced lignin, hyperaccumulation of flavonoids, and growth inhibition in Arabidopsis thaliana. It was previously reported that flavonoid-mediated inhibition of auxin transport is responsible for growth reduction in HCT-RNA interference (RNAi) plants. This conclusion was based on the observation that simultaneous RNAi silencing of HCT and chalcone synthase (CHS), an enzyme essential for flavonoid biosynthesis, resulted in less severe dwarfing than silencing of HCT alone. In an attempt to extend these results using a C39H mutant (ref8) and a CHS null mutant (tt4-2), we found that the growth phenotype of the ref8 tt4-2 double mutant, which lacks flavonoids, is indistinguishable from that of ref8. Moreover, using RNAi, we found that the relationship between HCT silencing and growth inhibition is identical in both the wild type and tt4-2. We conclude from these results that the growth inhibition observed in HCT-RNAi plants and the ref8 mutant is independent of flavonoids. Finally, we show that expression of a newly characterized gene bypassing HCT and C39H partially restores both lignin biosynthesis and growth in HCT-RNAi plants, demonstrating that a biochemical pathway downstream of coniferaldehyde, probably lignification, is essential for normal plant growth.