An essential role of caffeoyl shikimate esterase in monolignol biosynthesis in Medicago truncatula
An essential role of caffeoyl shikimate esterase in monolignol biosynthesis in Medicago truncatula
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DOI：
10.1111/tpj.13177
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发表时间：
2016-06-01
期刊：
影响因子：
7.2
通讯作者：
Dixon, Richard A.
中科院分区：
文献类型：
--
作者：
Ha, Chan Man;Escamilla-Trevino, Luis;Dixon, Richard A.
生化和遗传分析已经证实，咖啡酰莽草酸酯酶(CSE)是拟南芥单酚生物合成途径中的一种酶，尽管这一发现的普遍性受到了质疑。在这里，我们展示了木桶草属(Medicago truncatula，Dicot，豆科)、杨树(Pillius deltoides，Dicot，Salicaceae)和柳枝草(Panicum virgatum，Moncot，Poaceae)中CSE基因的存在及其相关的酶活性。在转座子插入系中，CSE功能的丧失导致严重矮化、发育变化、木质素含量降低和木质素中羟基苯基的优先积累，表明CSE酶是该物种正常木质化的关键。然而，模式草Brachypodium disachyon和玉米(Zea Mays)并不具有目前已鉴定的CSE基因的同源基因，而且这些物种的茎粗蛋白提取物只显示出与莽草酸咖啡酰的弱酯酶活性。我们的结果表明，CSE催化的反应可能不是所有植物木质化所必需的。
Biochemical and genetic analyses have previously identified caffeoyl shikimate esterase (CSE) as an enzyme in the monolignol biosynthesis pathway in Arabidopsis thaliana, although the generality of this finding has been questioned. Here we show the presence of CSE genes and associated enzyme activity in barrel medic (Medicago truncatula, dicot, Leguminosae), poplar (Populus deltoides, dicot, Salicaceae), and switchgrass (Panicum virgatum, monocot, Poaceae). Loss of function of CSE in transposon insertion lines of M. truncatula results in severe dwarfing, altered development, reduction in lignin content, and preferential accumulation of hydroxyphenyl units in lignin, indicating that the CSE enzyme is critical for normal lignification in this species. However, the model grass Brachypodium distachyon and corn (Zea mays) do not possess orthologs of the currently characterized CSE genes, and crude protein extracts from stems of these species exhibit only a weak esterase activity with caffeoyl shikimate. Our results suggest that the reaction catalyzed by CSE may not be essential for lignification in all plant species.