Gene duplication in the carotenoid biosynthetic pathway preceded evolution of the grasses
Gene duplication in the carotenoid biosynthetic pathway preceded evolution of the grasses
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DOI：
10.1104/pp.104.039818
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发表时间：
2004-07-01
期刊：
影响因子：
7.4
通讯作者：
Wurtzel, ET
中科院分区：
文献类型：
--
作者：
Gallagher, CE;Matthews, PD;Wurtzel, ET
尽管在模式生物中正在进行类胡萝卜素生物合成的研究，但在禾本科植物（包括具有世界范围农学重要性的植物）中操作的途径调节的信息缺乏。因此，对谷类作物中类胡萝卜素含量或组成的育种或代谢工程改进的努力导致了意想不到的结果。与玉米（Zea mays）相比，水稻（Oryza sativa）不积累胚乳类胡萝卜素，尽管在叶绿体中具有功能途径。为了更好地理解为什么这两种相关的草在胚乳类胡萝卜素含量上不同，我们开始表征编码八氢番茄红素合酶（PSY）的基因，因为这种核编码的酶似乎催化质体定位的生物合成途径中的速率控制步骤。该酶以前曾与玉米Y1位点相关联，被认为是控制PSY积累的唯一功能基因，尽管Y1基因产物的功能从未得到证实。我们发现，玉米和水稻都拥有和表达产品从重复PSY基因，PSY 1（Y1）和PSY 2; PSY 1转录积累与含类胡萝卜素胚乳。使用异源细菌系统，我们证明了酶的PSY 1和PSY 2的功能，在很大程度上保守的序列，除了N-和C-末端结构域。通过数据库挖掘和使用直向同源特异性通用PCR引物，我们发现PSY重复是普遍存在于至少8个亚科的禾本科，这表明这种重复事件之前的禾本科进化。这些发现将影响对全球粮食安全至关重要的整个植物作物分类组中的草的生殖和类胡萝卜素含量增加的育种研究。
Despite ongoing research on carotenoid biosynthesis in model organisms, there is a paucity of information on pathway regulation operating in the grasses (Poaceae), which include plants of world-wide agronomic importance. As a result, efforts to either breed for or metabolically engineer improvements in carotenoid content or composition in cereal crops have led to unexpected results. In comparison to maize (Zea mays), rice (Oryza sativa) accumulates no endosperm carotenoids, despite having a functional pathway in chloroplasts. To better understand why these two related grasses differ in endosperm carotenoid content, we began to characterize genes encoding phytoene synthase (PSY), since this nuclear-encoded enzyme appeared to catalyze a rate-controlling step in the plastid-localized biosynthetic pathway. The enzyme had been previously associated with the maize Y1 locus thought to be the only functional gene controlling PSY accumulation, though function of the Y1 gene product had never been demonstrated. We show that both maize and rice possess and express products from duplicate PSY genes, PSY1 (Y1) and PSY2; PSY1 transcript accumulation correlates with carotenoid-containing endosperm. Using a heterologous bacterial system, we demonstrate enzyme function of PSY1 and PSY2 that are largely conserved in sequence except for N- and C-terminal domains. By database mining and use of ortholog-specific universal PCR primers, we found that the PSY duplication is prevalent in at least eight subfamilies of the Poaceae, suggesting that this duplication event preceded evolution of the Poaceae. These findings will impact study of grass phylogeny and breeding of enhanced carotenoid content in an entire taxonomic group of plant crops critical for global food security.