《植物生理学报》 2021, 57(1): 169-177
通信作者：金维环；E-mail: firstname.lastname@example.org；郭红祥；E-mail: email@example.com
烟碱的合成受到众多因素的调控, 打顶是提高烟草(Nicotiana tabacum)中烟碱合成能力的一项重要栽培措施。为了阐述打顶调控烟碱合成的机制, 本文研究了NtMYC1在打顶调控烟碱生物合成中的功能。结果表明, 打顶和茉莉酸甲酯(MeJA)能显著增加NtMYC1a/1b的表达, 过表达NtMYC1a/1b能够显著提高NtPMT1/2的表达, 增加烟碱的含量, 而沉默NtMYC1a/1b能够降低NtPMT1/2的表达, 减少烟碱的含量, 说明该基因参与了烟碱的生物合成调控过程。酵母单杂交和凝胶迁移实验(EMSA)结果显示, NtMYC1a/1b转录因子能够与NtPMT1/2启动子的G-box识别结合, 说明NtMYC1a/1b通过与启动子G-box的结合调控NtPMT1/2基因的表达。以上结果证明烟草打顶诱导的茉莉酸除了激活释放NtMYC1a/1b外, 还能上调NtMYC1a/1b的表达, 增加烟草体内活性NtMYC1a/1b的含量, 进而提高NtPMT的表达, 促进烟碱的合成。
关键词：烟草; 打顶; 烟碱合成; NtMYC1; 调控
Corresponding author: JIN Weihuan; E-mail: firstname.lastname@example.org; GUO Hongxiang; E-mail: email@example.com
Nicotine synthesis can be regulated by many factors, and topping is an important cultural practices for improving the capability of nicotine synthesis in tobacco (Nicotiana tabacum). To illustrate the mechanism of topping-induced nicotine synthesis, the NtMYC1 function in topping-induced nicotine biosynthesis was studied. It was found that topping and MeJA could significantly increase the expression of NtMYC1a/1b. The research results of transgenic plants showed that the overexpression of NtMYC1a/1b could significantly increase the expression of NtPMT1/2 and the content of nicotine, and that the silence of NtMYC1a/1b could reduce the expression of NtPMT1/2 and the content of nicotine, indicating that NtMYC1a/1b was involved in the biosynthesis of nicotine. The results of yeast one-hybrid assay and EMSA showed that the NtMYC1a/1b transcription factors could recognize and bind to G-box in NtPMT1/2 promoter, illustrating that NtMYC1a/1b can regulate the expression of NtPMT1/2 through by combining with the G-box. Therefore, topping and the induced JA can not only activate NtMYC1a/1b through its release from the ternary complex, but also raise the expression of NtMYC1a/1b. The increase of active NtMYC1a/1b could enhance the expression of NtPMT, and then promote the synthesis of nicotine.
Key words: Nicotiana tabacum; topping; nicotine synthesis; NtMYC1; regulation
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