The Evolution and Function of Carotenoid Hydroxylases in Arabidopsis
The Evolution and Function of Carotenoid Hydroxylases in Arabidopsis
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DOI：
10.1093/pcp/pcp005
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发表时间：
2009-03-01
影响因子：
4.9
通讯作者：
DellaPenna, Dean
中科院分区：
文献类型：
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作者：
Kim, Joonyul;Smith, James J.;DellaPenna, Dean
为了深入了解拟南芥中叶黄素合成的进化，我们分析了拟南芥中两对重复的类胡萝卜素羟化酶：细胞色素P450酶CYP 97 A3和CYP 97 C1，以及非血红素二铁酶BCH 1和BCH 2。羟基化胡萝卜素在这四个基因的四重突变体中没有积累，表明它们编码A. thaliana.因此，我们能够明确地推断活性的每种酶在体内的基础上选择的双重和三重突变基因型的表型。CYP 97和BCH基因对主要负责羟基化的-和-胡萝卜素，分别，但表现出一些重叠的活动，最显着的羟基化的-环的-胡萝卜素。令人惊讶的是，只含有CYP 97 C1或CYP 97 A3活性的三重突变体产生了野生型叶黄素水平的74和6，表明CYP 97 C1可以有效地羟基化β-胡萝卜素的β-和β-环，CYP 97 A3对β-胡萝卜素的β-环也具有低活性。基因对的功能分化模式似乎不同，CYP 97重复被强烈共表达，但编码的酶与不同的体内底物，而BCH重复编码的同工酶，在生殖器官中表现出显着的表达分化。通过整合的进化历史和底物特异性的每一个现存的酶与各种突变基因型的表型反应，高光胁迫，我们提出了两个可能的情况下的进化-叶黄素生物合成的植物从祖先的生物。
To gain insight into the evolution of xanthophyll synthesis in Arabidopsis thaliana, we analyzed two pairs of duplicated carotenoid hydroxylase enzymes in Arabidopsis thaliana: the cytochrome P450 enzymes CYP97A3 and CYP97C1, and non-heme di-iron enzymes, BCH1 and BCH2. Hydroxylated carotenes did not accumulate in a quadruple mutant for these four genes, demonstrating that they encode the full complement of carotenoid hydroxylases in A. thaliana. We were thus able to infer definitively the activity of each enzyme in vivo based on the phenotypes of selected double and triple mutant genotypes. The CYP97 and BCH gene pairs are primarily responsible for hydroxylation of - and -carotenes, respectively, but exhibit some overlapping activities, most notably in hydroxylation of the -ring of -carotene. Surprisingly, triple mutants containing only CYP97C1 or CYP97A3 activity produced 74 and 6 of the wild-type lutein level, indicating that CYP97C1 can efficiently hydroxylate both the - and -rings of -carotene and that CYP97A3 also has low activity toward the -ring of -carotene. The modes of functional divergence for the gene pairs appear distinct, with the CYP97 duplicates being strongly co-expressed but encoding enzymes with different in vivo substrates, while the BCH duplicates encode isozymes that show significant expression divergence in reproductive organs. By integrating the evolutionary history and substrate specificities of each extant enzyme with the phenotypic responses of various mutant genotypes to high light stress, we propose two likely scenarios for the evolution of -xanthophyll biosynthesis in plants from ancestral organisms.