Tobacco Breeding Center, Yunnan Academy of Tobacco Agricultural Sciences, Kunming, China.
Technology Center, Baoshan Oriental Tobacco Company, Baoshan, China.
Plant Biol (Stuttg). 2021 Mar;23(2):317-326. doi: 10.1111/plb.13223. Epub 2021 Jan 13.
The biosynthesis and transport of nicotine has been shown to be coordinately upregulated by jasmonate (JA). MYC2, a member of basic helix-loop-helix (bHLH) transcription factor family, is well-documented as the core player in the JA signalling pathway to regulate diverse plant development processes. Four MYC2 genes were found in the tobacco genome, NtMYC2a/2b and 1a/1b. In this study, we tested whether one of them, NtMYC2a, acts as a 'master switch' in the regulation of nicotine biosynthesis and transport in tobacco. We generated NtMYC2a knockout tobacco plants using the CRISPR-Cas9 technique and analysed the effect of NtMYC2a knockout on expression of the nicotine biosynthesis genes (NtAO, NtQS, NtPMT1a, NtQPT2, NtODC2, NtMPO1, NtA622 and NtBBLa) and transport genes (NtMATE2 and NtJAT1), as well as leaf accumulation of nicotine in the NtMYC2a knockout plants. We found that all the nicotine biosynthesis and transport genes tested in this study were significantly downregulated (>50% reduction compared with wild-type control) in the NtMYC2a knockout plants. Moreover, the leaf nicotine content in knockout plants was dramatically reduced by ca 80% compared with the wild-type control. These results clearly show that NtMYC2a acts as a 'master switch' to coordinate JA-induced nicotine accumulation in tobacco and suggests that NtMYC2a might play an important role in tobacco nicotine-mediated defence against herbivory.
茉莉酸（JA）被证明能协调上调尼古丁的生物合成和运输。MYC2 是基本螺旋-环-螺旋（bHLH）转录因子家族的成员，它是 JA 信号通路中调节多种植物发育过程的核心因子，这一点已有充分的文献记载。在烟草基因组中发现了四个 MYC2 基因，即 NtMYC2a/2b 和 1a/1b。在这项研究中，我们测试了其中一个基因，NtMYC2a 是否在烟草中尼古丁生物合成和运输的调节中充当“主开关”。我们使用 CRISPR-Cas9 技术生成了 NtMYC2a 敲除烟草植物，并分析了 NtMYC2a 敲除对尼古丁生物合成基因（NtAO、NtQS、NtPMT1a、NtQPT2、NtODC2、NtMPO1、NtA622 和 NtBBLa）和运输基因（NtMATE2 和 NtJAT1）表达以及 NtMYC2a 敲除植物叶片中尼古丁积累的影响。我们发现，在 NtMYC2a 敲除植物中，所有测试的尼古丁生物合成和运输基因均显著下调（与野生型对照相比，下调超过 50%）。此外，与野生型对照相比，敲除植物的叶片尼古丁含量降低了约 80%。这些结果清楚地表明，NtMYC2a 作为“主开关”协调 JA 诱导的烟草中尼古丁积累，并表明 NtMYC2a 可能在烟草尼古丁介导的抗食草性防御中发挥重要作用。
