Zhou Baifeng, Shima Hiroki, Igarashi Kazuhiko, Tanaka Kan, Imamura Sousuke
School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan.
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan.
Front Plant Sci. 2022 Mar 11;13:821947. doi: 10.3389/fpls.2022.821947. eCollection 2022.
Nitrogen assimilation is an essential process that controls plant growth and development. Plant cells adjust the transcription of nitrogen assimilation genes through transcription factors (TFs) to acclimatize to changing nitrogen levels in nature. However, the regulatory mechanisms of these TFs under nitrogen-repleted (+N) conditions in plant lineages remain largely unknown. Here, we identified a negative domain (ND) of CmMYB1, the nitrogen-depleted (-N)-activated TF, in a unicellular red alga . The ND deletion changed the localization of CmMYB1 from the cytoplasm to the nucleus, enhanced the binding efficiency of CmMYB1 to promoters of nitrate assimilation genes, and increased the transcripts of nitrate assimilation genes under +N condition. A pull-down assay using an ND-overexpressing strain combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis helped us to screen and identify an unknown-function protein, the CmNDB1. Yeast two-hybrid analysis demonstrated that CmNDB1 interacts with ND. Similar to ND deletion, deletion also led to the nucleus localization of CmMYB1, enhanced the promoter-binding ratio of CmMYB1 to the promoter regions of nitrate assimilation genes, and increased transcript levels of nitrate assimilation genes under +N condition. Thus, these presented results indicated that ND and CmNDB1 negatively regulate CmMYB1 functions under the +N condition in .
氮同化是控制植物生长发育的一个重要过程。植物细胞通过转录因子（TFs）来调节氮同化基因的转录，以适应自然界中不断变化的氮水平。然而，在植物谱系中，这些转录因子在氮充足（+N）条件下的调控机制仍 largely 未知。在这里，我们在单细胞红藻中鉴定出了氮缺乏（-N）激活的转录因子 CmMYB1 的一个负调控域（ND）。ND 的缺失将 CmMYB1 的定位从细胞质改变到细胞核，增强了 CmMYB1 与硝酸盐同化基因启动子的结合效率，并在 +N 条件下增加了硝酸盐同化基因的转录本。使用过表达 ND 的菌株结合液相色谱 - 串联质谱（LC-MS/MS）分析的下拉实验帮助我们筛选并鉴定了一种功能未知的蛋白质 CmNDB1。酵母双杂交分析表明 CmNDB1 与 ND 相互作用。与 ND 缺失类似，[此处原文缺失部分内容]缺失也导致 CmMYB1 的细胞核定位，增强了 CmMYB1 与硝酸盐同化基因启动子区域的启动子结合比例，并在 +N 条件下增加了硝酸盐同化基因的转录水平。因此，这些呈现的结果表明，在 +N 条件下，ND 和 CmNDB1 在[此处原文缺失部分内容]中对 CmMYB1 的功能起负调控作用。
