Recruitment of a duplicated primary metabolism gene into the nicotine biosynthesis regulon in tobacco
Recruitment of a duplicated primary metabolism gene into the nicotine biosynthesis regulon in tobacco
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DOI：
10.1111/j.1365-313x.2011.04647.x
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发表时间：
2011-09-01
期刊：
影响因子：
7.2
通讯作者：
Hashimoto, Takashi
中科院分区：
文献类型：
--
作者：
Shoji, Tsubasa;Hashimoto, Takashi
基因复制是植物表型多样性的一个重要来源，但在复制基因中产生新功能的分子机制还没有完全记录。在这里，我们分析了重复的基因编码的喹啉磷酸核糖转移酶（QPT），参与烟酰胺腺嘌呤二核苷酸（NAD）和尼古丁的吡啶部分的合成酶，是由茉莉酸响应转录因子ERF 189，在烟草（烟草）尼古丁生物合成的关键功能调节。烟草基因组含有重复的QPT基因; QPT 1在组成性基础水平表达，而QPT 2与参与尼古丁生物合成的其他结构基因在组织特异性、茉莉酸诱导和ERF 189调节方面协调调节。利用烟草腐胺N-甲基转移酶启动子将ERF 189的结合位点特异性定义为5 '-（A/C）GC（A/C）（A/C）NCC-3'，并在QPT启动子中寻找潜在的结合位点。涉及体外DNA结合，瞬时反式激活，和转基因毛状根的分析表明，QPT 2启动子含有三个功能ERF 189结合位点，分别赋予增量ERF 189介导的激活启动子。QPT 1启动子不受ERF 189的结合和调节。这些结果表明，重复的QPT基因的一个拷贝被招募到烟草生物碱调节子的ERF 189在其启动子中的多个目标顺式调节元件的演变，以科普增加的代谢需求吡啶前体活性生物碱生物合成过程中。
Gene duplication is a powerful source of phenotypic diversity in plants, but the molecular mechanisms that generate new functions in duplicated genes are not fully documented. Here, we analyzed how duplicated genes encoding quinolinate phosphoribosyltransferase (QPT), an enzyme involved in the synthesis of nicotinamide adenine dinucleotide (NAD) and the pyridine moiety of nicotine, are regulated by the jasmonate-responsive transcriptional factor ERF189 that functions critically for nicotine biosynthesis in tobacco (Nicotiana tabacum). The tobacco genome contains duplicated QPT genes; QPT1 is expressed at a constitutive basal level, whereas QPT2 is regulated coordinately with other structural genes involved in nicotine biosynthesis, in terms of tissue specificity, jasmonate induction, and regulation by ERF189. The binding-site specificity of ERF189 was defined as 5'-(A/C) GC(A/C)(A/C) NCC-3' by using a characterized tobacco putrescine N-methyltransferase promoter, and was then used to search for potential binding sites in the QPT promoters. Assays involving in vitro DNA binding, transient transactivation, and transgenic hairy roots revealed that the QPT2 promoter contains three functional ERF189-binding sites, which individually confer incremental ERF189-mediated activation to the promoter. The QPT1 promoter is not bound and regulated by ERF189. These results indicate that one copy of the duplicated QPT genes was recruited to a tobacco alkaloid regulon by evolving multiple target cis-regulatory elements of ERF189 in its promoter, to cope with an increased metabolic demand for pyridine precursors during active alkaloid biosynthesis.