APETALA2/ETHYLENE RESPONSE FACTOR and basic helix-loop-helix tobacco transcription factors cooperatively mediate jasmonate-elicited nicotine biosynthesis
APETALA2/ETHYLENE RESPONSE FACTOR and basic helix-loop-helix tobacco transcription factors cooperatively mediate jasmonate-elicited nicotine biosynthesis
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DOI：
10.1111/j.1365-313x.2011.04566.x
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发表时间：
2011-06-01
期刊：
影响因子：
7.2
通讯作者：
Goossens, Alain
中科院分区：
文献类型：
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作者：
De Boer, Kathleen;Tilleman, Sofie;Goossens, Alain
植物特异性 apetala2/乙烯反应因子 (AP2/ERF) 家族的转录因子控制植物次生代谢，通常作为茉莉酸 (JA) 或其他诱导子诱导的信号级联的一部分。在这里，我们对 JA 诱导烟草 (Nicotiana tabacum) AP2/ERF 因子 ORC1 进行了功能表征，ORC1 是控制尼古丁生物合成的 NIC2 位点 ERF 的成员之一，也是 ORCA3 的密切同源物，ORCA3 是长春花中生物碱生物合成的转录激活剂。 ORC1 正向调节编码参与尼古丁生物合成的酶的几个结构基因的转录。因此，ORC1 的过度表达足以刺激烟草植物和烟草 (Nicotiana glauca) 根培养物中的生物碱生物合成。与玫瑰花中的 ORCA3 不同，ORC1 需要烟草尼古丁生物合成基因的启动子中同时存在 GCC 基序和 G-box 元件，以实现最大程度的反式激活。相应地，与结合这些启动子中的 G-box 元件的 JA 诱导型烟草碱性螺旋-环-螺旋 (bHLH) 因子的联合应用增强了 ORC1 的作用。相反，阻断 bHLH 活性的 JAZ 阻遏蛋白的过度积累会降低 ORC1 的功能。最后，ORC1 和 bHLH 蛋白的活性均通过 JA 调节的磷酸化级联进行翻译后上调，其中鉴定出一种特定的丝裂原激活蛋白激酶激酶，即 JA 因子刺激 MAPKK1 (JAM1)。这项研究强调了参与烟草生物碱生物合成调节的分子机制的复杂性，并提供了有关其转录调节因子的机制见解。
Transcription factors of the plant-specific apetala2/ethylene response factor (AP2/ERF) family control plant secondary metabolism, often as part of signalling cascades induced by jasmonate (JA) or other elicitors. Here, we functionally characterized the JA-inducible tobacco (Nicotiana tabacum) AP2/ERF factor ORC1, one of the members of the NIC2-locus ERFs that control nicotine biosynthesis and a close homologue of ORCA3, a transcriptional activator of alkaloid biosynthesis in Catharanthus roseus. ORC1 positively regulated the transcription of several structural genes coding for the enzymes involved in nicotine biosynthesis. Accordingly, overexpression of ORC1 was sufficient to stimulate alkaloid biosynthesis in tobacco plants and tree tobacco (Nicotiana glauca) root cultures. In contrast to ORCA3 in C. roseus, which needs only the GCC motif in the promoters of the alkaloid synthesis genes to induce their expression, ORC1 required the presence of both GCC-motif and G-box elements in the promoters of the tobacco nicotine biosynthesis genes for maximum transactivation. Correspondingly, combined application with the JA-inducible Nicotiana basic helix-loop-helix (bHLH) factors that bind the G-box element in these promoters enhanced ORC1 action. Conversely, overaccumulation of JAZ repressor proteins that block bHLH activity reduced ORC1 functionality. Finally, the activity of both ORC1 and bHLH proteins was post-translationally upregulated by a JA-modulated phosphorylation cascade, in which a specific mitogen-activated protein kinase kinase, JA-factor stimulating MAPKK1 (JAM1), was identified. This study highlights the complexity of the molecular machinery involved in the regulation of tobacco alkaloid biosynthesis and provides mechanistic insights about its transcriptional regulators.