Takagi Hiroshi, Ito Shogo, Shim Jae Sung, Kubota Akane, Hempton Andrew K, Lee Nayoung, Suzuki Takamasa, Yang Chansie, Nolan Christine T, Bubb Kerry L, Alexandre Cristina M, Kurihara Daisuke, Sato Yoshikatsu, Tada Yasuomi, Kiba Takatoshi, Pruneda-Paz Jose L, Queitsch Christine, Cuperus Josh T, Imaizumi Takato
Department of Biology, University of Washington, Seattle, Washington, 98195, USA.
Center for Gene Research, Nagoya University, Nagoya, 464-8602, Japan.
bioRxiv. 2024 Aug 19:2024.08.17.608367. doi: 10.1101/2024.08.17.608367.
The precise onset of flowering is crucial to ensure successful plant reproduction. The gene () encodes florigen, a mobile signal produced in leaves that initiates flowering at the shoot apical meristem. In response to seasonal changes, is induced in phloem companion cells located in distal leaf regions. Thus far, a detailed molecular characterization of the -expressing cells has been lacking. Here, we used bulk nuclei RNA-seq and single nuclei RNA (snRNA)-seq to investigate gene expression in -expressing cells and other phloem companion cells. Our bulk nuclei RNA-seq demonstrated that -expressing cells in cotyledons and in true leaves differed transcriptionally. Within the true leaves, our snRNA-seq analysis revealed that companion cells with high expression form a unique cluster in which many genes involved in ATP biosynthesis are highly upregulated. The cluster also expresses other genes encoding small proteins, including the flowering and stem growth inducer FPF1-LIKE PROTEIN 1 (FLP1) and the anti-florigen BROTHER OF FT AND TFL1 (BFT). In addition, we found that the promoters of and the genes co-expressed with in the cluster were enriched for the consensus binding motifs of NITRATE-INDUCIBLE GARP-TYPE TRANSCRIPTIONAL REPRESSOR 1 (NIGT1). Overexpression of the paralogous and repressed expression and significantly delayed flowering under nitrogen-rich conditions, consistent with NIGT1s acting as nitrogen-dependent repressors. Taken together, our results demonstrate that major -expressing cells show a distinct expression profile that suggests that these cells may produce multiple systemic signals to regulate plant growth and development.
精确的开花起始对于确保植物繁殖成功至关重要。基因（）编码成花素，这是一种在叶片中产生的可移动信号，它在茎尖分生组织处启动开花。响应季节变化，在位于远端叶区域的韧皮部伴胞中被诱导。到目前为止，一直缺乏对表达该基因的细胞的详细分子特征描述。在这里，我们使用批量细胞核RNA测序和单核RNA（snRNA）测序来研究表达该基因的细胞和其他韧皮部伴胞中的基因表达。我们的批量细胞核RNA测序表明，子叶和真叶中表达该基因的细胞在转录上存在差异。在真叶中，我们的snRNA测序分析表明，高表达该基因的伴胞形成了一个独特的簇，其中许多参与ATP生物合成的基因被高度上调。该簇还表达其他编码小蛋白的基因，包括开花和茎生长诱导因子类成花素结合蛋白1（FLP1）和抗成花素FT和TFL1的同源蛋白（BFT）。此外，我们发现该基因以及在该簇中与它共表达的基因的启动子富含硝酸盐诱导型GARP类转录抑制因子1（NIGT1）的共有结合基序。同源基因和的过表达抑制了该基因的表达，并在富氮条件下显著延迟了开花，这与NIGT1作为氮依赖性该基因的抑制因子的作用一致。综上所述，我们的结果表明，主要表达该基因的细胞呈现出独特的表达谱，这表明这些细胞可能产生多种系统性信号来调节植物的生长和发育。
