RIKEN Center for Sustainable Resource Science, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.
Division of Biological Science, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101, Japan.
Plant J. 2022 Sep;111(6):1768-1779. doi: 10.1111/tpj.15923. Epub 2022 Aug 11.
In tobacco, the homologous ETHYLENE RESPONSE FACTOR (ERF) transcription factors ERF199 and ERF189 coordinate the transcription of multiple metabolic genes involved in nicotine biosynthesis. Natural alleles at the NIC1 and NIC2 loci greatly affect alkaloid accumulation and overlap with ERF199 and ERF189 in the tobacco genome, respectively. In this study, we identified several low-nicotine tobacco varieties lacking ERF199 or ERF189 from a tobacco germplasm collection. We characterized the sequence of these new nic1 and nic2 alleles, as well as the previously defined alleles nic1-1 and nic2-1. Moreover, we examined the influence of different nic alleles on alkaloid contents and expression levels of genes related to nicotine biosynthesis. We also demonstrated that the deletion of a distal genomic region attenuates ERF199 expression, resulting in a moderately negative effect on the alkaloid phenotype. Our study provides new insights into the regulation of nicotine biosynthesis and novel genetic resources to breed low-nicotine tobacco.
在烟草中，同源的 ETHYLENE RESPONSE FACTOR（ERF）转录因子 ERF199 和 ERF189 协调参与尼古丁生物合成的多个代谢基因的转录。NIC1 和 NIC2 基因座的天然等位基因极大地影响生物碱的积累，并且分别与烟草基因组中的 ERF199 和 ERF189 重叠。在这项研究中，我们从烟草种质资源中鉴定出几种缺乏 ERF199 或 ERF189 的低尼古丁烟草品种。我们对这些新的 nic1 和 nic2 等位基因的序列进行了表征，以及先前定义的 nic1-1 和 nic2-1 等位基因。此外，我们还研究了不同 nic 等位基因对生物碱含量和与尼古丁生物合成相关基因表达水平的影响。我们还证明，远端基因组区域的缺失会削弱 ERF199 的表达，从而对生物碱表型产生适度的负面影响。我们的研究为尼古丁生物合成的调控提供了新的见解，并为培育低尼古丁烟草提供了新的遗传资源。
