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the plant journal：植物陆地化过程中香豆酰共轭体系3-羟化酶的演化

已有 2702 次阅读 2019-5-9 16:03 |个人分类:每日摘要|系统分类:论文交流

Evolution of coumaroyl conjugate 3‐hydroxylases in land plants: Lignin biosynthesis and defense

First author: Annette V. Alber; Affiliations: University of Strasbourg (斯特拉斯堡大学): Strasbourg, France

Corresponding author: Jürgen Ehlting

When plants conquered land, multiple adaptations were necessary. Among them were soluble phenylpropanoids related to plant protection and lignin necessary for upright growth and long‐distance water transport. The cytochrome P450 monooxygenase CYP98 catalyses a rate‐limiting step in phenylpropanoid biosynthesis. Phylogenetic reconstructions suggest that a single copy CYP98 founded each major land plant lineage (bryophytes, lycophytes, monilophytes, gymnosperms, and angiosperms), which was maintained in single copy in all lineages but the angiosperms. In angiosperms, a series of independent gene duplications and losses occured. Based on biochemical assays, in each of four angiosperm species tested, 4‐coumaroyl‐shikimate, a known intermediate in lignin biosynthesis, was the preferred substrate of one member, while independent duplicates in Populus trichocarpa and Amborella trichopoda each showed broad substrate ranges, accepting numerous 4‐coumaroyl‐esters and ‐amines, and thus were capable of producing a wide range of hydroxycinnamoyl‐conjugates. The gymnosperm CYP98 from Pinus taeda showed a broad substrate range, but prefered 4‐coumaroyl‐shikimate as its best substrate. In contrast, CYP98s from the lycophyte Selaginella moellendorffii and the fern Pteris vittata converted 4‐coumaroyl‐shikimate poorly in vitro, but were able to use alternative substrates, in particular 4‐coumaroyl‐anthranilate. Thus, caffeoyl‐shikimate appears unlikely to be an intermediate in monolignol biosynthesis in non‐seed vascular plants including ferns. 4‐coumaroyl‐anthranilate was also the best substrate for CYP98A34 from the moss Physcomitrella patens, while 4‐coumaroyl‐shikimate was converted to lower extents. Despite having in vitro activity with 4‐coumaroyl‐shikimate, CYP98A34 was unable to complement the Arabidopsis thaliana cyp98a3 loss of function phenotype, suggesting distinct properties also in vivo.

当植物开始征服陆地时，必需经历多个适应性演化。其中就有可溶性苯丙烷类物质，这类物质与植物保护和木质素的合成息息相关，而木质素则是植物向上生长以及长距离水分运输的必需成分。细胞色素P450单加氧酶CYP98催化一个苯丙烷生物合成通路中的限速反应。系统发育学分析显示在苔藓类、石松类、广义真蕨类、裸子植物和被子植物等所有主要的陆地植物谱系中均有一个CYP98的拷贝，而其除了在被子植物中，在其他所有谱系中均只保持了一个拷贝。在被子植物中，发生了一系列独立的基因复制和丢失事件。基于生化试验的结果，在四个被子植物物种中，一个木质素合成通路上的中间产物4-香豆酰-莽草酸酯是优先被选择的底物，而在毛果杨和无油樟中的独立基因复制事件产生了各种类型的底物，包括各种各样的4-香豆酰-酯类和4-香豆酰-胺类，因此能产生各种各样的羟基肉桂基-共轭物。来自裸子植物火炬松中的CYP98显示出广泛的底物范围，但4-香豆酰-莽草酸酯依旧是其首选的底物。相反，来自石松类植物江南卷柏和蕨类植物羊齿蕨的CYP98在体外对于4-香豆酰-莽草酸酯的转化率很低，但可以使用代替性的底物，尤其是4-香豆酰-邻氨基苯甲酸。因此，咖啡酰-莽草酸酯显然不可能是包括蕨类植物在内的非种子维管植物木质素单体生物合成的中间产物。4-香豆酰-邻氨基苯甲酸同时也是苔藓植物小立碗藓CYP98A34的最优底物，而CYP98A34对于4-香豆酰-莽草酸酯的转化率很低。除了体外对于4-香豆酰-莽草酸酯的酶活很低之外，CYP98A34不能互补拟南芥的cyp98a3功能缺失突变体表型，说明体内这两个酶也具有明显不同的特性。