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烟草C2H2-ZFP转录因子家族鉴定及NtZFP26基因调控烟碱合成的功能分析

Identification of the C2H2-ZFP Transcription Factor Family and Functional Analysis of NtZFP26 in Regulating Nicotine Synthesis in Tobacco

  • 摘要: 为明确C2H2型锌指蛋白(C2H2-ZFP)在烟草烟碱合成中的作用,基于普通烟草K326全基因组鉴定出131个NtC2H2-ZFP成员,系统进化分析将其分为6个亚家族。启动子与转录组分析表明,家族成员表达具有显著的组织特异性与胁迫响应特性,且启动子区域富含光响应与激素响应元件。结合表达模式与共表达网络分析,筛选出候选基因NtZFP26。该基因在烟碱合成关键部位根部皮层组织中特异性高表达,其表达受打顶与茉莉酸甲酯(MeJA)显著诱导,且与烟碱合成关键基因NtPMT2NtPMT3NtPMT4NtBBL共表达。功能验证显示,CRISPR/Cas9敲除突变体ntzfp26根和叶中烟碱含量显著降低,相关合成基因表达下调。酵母单杂交和双荧光素酶报告实验表明,NtZFP26可直接结合烟碱合成限速酶基因NtQPT2启动子并激活其转录。综上,NtZFP26是烟草烟碱合成通路的关键正调控因子,通过激活NtQPT2表达促进烟碱积累。

     

    Abstract: To elucidate the role of C2H2-type zinc finger proteins (C2H2-ZFP) in tobacco nicotine synthesis, 131 transcription factor family members of NtC2H2-ZFP were identified from the genome of common tobacco K326 via genome-wide identification. Phylogenetic analysis classified these members into 6 subfamilies. Promoter and transcriptome analyses revealed that NtC2H2-ZFP family members exhibited distinct expression patterns characterized by significant tissue specificity and stress responsiveness, and their promoter regions were enriched in light- and hormone-responsive elements. Through further integration of expression pattern and co-expression analyses, NtZFP26 was selected as a candidate gene associated with nicotine synthesis. It showed specific high expression in the root cortex—the key site of nicotine synthesis—and was significantly induced by topping and methyl jasmonate (MeJA). Moreover, NtZFP26 was co-expressed with key nicotine biosynthesis genes, including NtPMT2, NtPMT3, NtPMT4 and NtBBL. Functional verification demonstrated that the ntzfp26 mutant generated by CRISPR/Cas9 technology showed a marked decrease in nicotine content in both roots and leaves compared with the wild type, accompanied by downregulated expression of key nicotine synthesis genes. Yeast one‑hybrid and dual‑luciferase reporter assays confirmed that NtZFP26 directly binds to the promoter of the rate‑limiting enzyme gene NtQPT2 and activates its transcription. In summary, NtZFP26 acts as a key positive regulator in the tobacco nicotine biosynthesis pathway, and regulates nicotine accumulation by activating NtQPT2 expression.

     

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