Evolution of a secondary metabolic pathway from primary metabolism: shikimate and quinate biosynthesis in plants
Evolution of a secondary metabolic pathway from primary metabolism: shikimate and quinate biosynthesis in plants
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DOI：
10.1111/tpj.13990
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发表时间：
2018-09-01
期刊：
影响因子：
7.2
通讯作者：
Ehlting, Jurgen
中科院分区：
文献类型：
--
作者：
Carrington, Yuriko;Guo, Jia;Ehlting, Jurgen
莽草酸途径合成蛋白质生物合成所必需的芳香族氨基酸。莽草酸脱氢酶(SDH)是这一主要代谢途径的中心酶，产生莽草酸。结构相似奎尼酸是奎尼酸脱氢酶(QDH)合成的次生代谢物。SDH和qdh属于同一基因家族，在被子植物/裸子植物分裂前的一次决定性基因复制后，这两个基因分化为两个系统发育分支。在这种复制之前分化的非种子植物只有一个这个家族的基因。现存的叶绿藻(Chlamydomonas Reinhardtii)、苔藓植物(Physcomitrella Patens)和番茄(Selaginella Moellendorfii)的代表植物在体外几乎只编码SDH活性。代表基因复制之前节点的重建的祖先序列也编码了SDH活性。奎尼酸脱氢酶活性只有在基因复制后才能在种子植物中获得。裸子植物的奎尼酸脱氢酶，这里以火炬松为代表，可能让人联想到进化的中间产物，因为它们编码相同的SDH和QDH活性。在P.taeda中的第二个拷贝保持了对莽草酸的特异性，类似于在被子植物SDH姊妹分支中发现的活性。活性部位内酪氨酸残基的密码子在定义QDH分支的节点处显示出正选择的特征，在那里它变成了甘氨酸。在高度莽草酸专一性的被子植物SDH中，用甘氨酸取代酪氨酸足以获得一些QDH功能。因此，几乎没有突变是必要的，以促进qdh基因的进化。
The shikimate pathway synthesizes aromatic amino acids essential for protein biosynthesis. Shikimate dehydrogenase (SDH) is a central enzyme of this primary metabolic pathway, producing shikimate. The structurally similar quinate is a secondary metabolite synthesized by quinate dehydrogenase (QDH). SDH and QDH belong to the same gene family, which diverged into two phylogenetic clades after a defining gene duplication just prior to the angiosperm/gymnosperm split. Non-seed plants that diverged before this duplication harbour only a single gene of this family. Extant representatives from the chlorophytes (Chlamydomonas reinhardtii), bryophytes (Physcomitrella patens) and lycophytes (Selaginella moellendorfii) encoded almost exclusively SDH activity invitro. A reconstructed ancestral sequence representing the node just prior to the gene duplication also encoded SDH activity. Quinate dehydrogenase activity was gained only in seed plants following gene duplication. Quinate dehydrogenases of gymnosperms, represented here by Pinus taeda, may be reminiscent of an evolutionary intermediate since they encode equal SDH and QDH activities. The second copy in P. taeda maintained specificity for shikimate similar to the activity found in the angiosperm SDH sister clade. The codon for a tyrosine residue within the active site displayed a signature of positive selection at the node defining the QDH clade, where it changed to a glycine. Replacing the tyrosine with a glycine in a highly shikimate-specific angiosperm SDH was sufficient to gain some QDH function. Thus, very few mutations were necessary to facilitate the evolution of QDH genes.