Luck Katrin, Jia Qidong, Huber Meret, Handrick Vinzenz, Wong Gane Ka-Shu, Nelson David R, Chen Feng, Gershenzon Jonathan, Köllner Tobias G
Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, 07745, Jena, Germany.
Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN, 37996, USA.
Plant Mol Biol. 2017 Sep;95(1-2):169-180. doi: 10.1007/s11103-017-0646-0. Epub 2017 Aug 9.
Conifers contain P450 enzymes from the CYP79 family that are involved in cyanogenic glycoside biosynthesis. Cyanogenic glycosides are secondary plant compounds that are widespread in the plant kingdom. Their biosynthesis starts with the conversion of aromatic or aliphatic amino acids into their respective aldoximes, catalysed by N-hydroxylating cytochrome P450 monooxygenases (CYP) of the CYP79 family. While CYP79s are well known in angiosperms, their occurrence in gymnosperms and other plant divisions containing cyanogenic glycoside-producing plants has not been reported so far. We screened the transcriptomes of 72 conifer species to identify putative CYP79 genes in this plant division. From the seven resulting full-length genes, CYP79A118 from European yew (Taxus baccata) was chosen for further characterization. Recombinant CYP79A118 produced in yeast was able to convert L-tyrosine, L-tryptophan, and L-phenylalanine into p-hydroxyphenylacetaldoxime, indole-3-acetaldoxime, and phenylacetaldoxime, respectively. However, the kinetic parameters of the enzyme and transient expression of CYP79A118 in Nicotiana benthamiana indicate that L-tyrosine is the preferred substrate in vivo. Consistent with these findings, taxiphyllin, which is derived from L-tyrosine, was the only cyanogenic glycoside found in the different organs of T. baccata. Taxiphyllin showed highest accumulation in leaves and twigs, moderate accumulation in roots, and only trace accumulation in seeds and the aril. Quantitative real-time PCR revealed that CYP79A118 was expressed in plant organs rich in taxiphyllin. Our data show that CYP79s represent an ancient family of plant P450s that evolved prior to the separation of gymnosperms and angiosperms. CYP79A118 from T. baccata has typical CYP79 properties and its substrate specificity and spatial gene expression pattern suggest that the enzyme contributes to the formation of taxiphyllin in this plant species.
针叶树含有来自CYP79家族的细胞色素P450酶，这些酶参与生氰糖苷的生物合成。生氰糖苷是植物界广泛存在的次生植物化合物。它们的生物合成始于芳香族或脂肪族氨基酸在CYP79家族的N-羟基化细胞色素P450单加氧酶（CYP）催化下转化为各自的醛肟。虽然CYP79在被子植物中广为人知，但迄今为止尚未报道它们在裸子植物和其他含有生氰糖苷的植物类群中的存在情况。我们筛选了72种针叶树的转录组，以鉴定该植物类群中假定的CYP79基因。从得到的7个全长基因中，选择了欧洲红豆杉（Taxus baccata）的CYP79A118进行进一步表征。在酵母中产生的重组CYP79A118能够分别将L-酪氨酸、L-色氨酸和L-苯丙氨酸转化为对羟基苯乙醛肟、吲哚-3-乙醛肟和苯乙醛肟。然而，该酶的动力学参数以及CYP79A118在本氏烟草中的瞬时表达表明，L-酪氨酸是体内的首选底物。与这些发现一致，源自L-酪氨酸的紫杉叶素是在欧洲红豆杉不同器官中发现的唯一生氰糖苷。紫杉叶素在叶片和嫩枝中积累最高，在根中积累适中，在种子和假种皮中仅微量积累。定量实时PCR显示CYP79A118在富含紫杉叶素的植物器官中表达。我们的数据表明，CYP79代表了一个古老的植物P450家族，在裸子植物和被子植物分离之前就已进化。欧洲红豆杉的CYP79A118具有典型的CYP79特性，其底物特异性和空间基因表达模式表明该酶有助于该植物物种中紫杉叶素的形成。
