Instituto de Bioquímica Vegetal y Fotosíntesis, Consejo Superior de Investigaciones Científicas and Universidad de Sevilla, Américo Vespucio 49, E-41092, Seville, Spain.
Laboratory for Microbiology, Faculty of Biology, Philipps University, Marburg, Germany.
Sci Rep. 2019 Feb 26;9(1):2744. doi: 10.1038/s41598-019-39336-6.
The organismic unit of heterocyst-forming cyanobacteria is a filament of communicating cells connected by septal junctions, proteinaceous structures bridging the cytoplasms of contiguous cells. This distinct bacterial organization is preserved during cell division. In Anabaena, deletion of the zipN gene could not be segregated. We generated strain CSL109 that expresses zipN from a synthetic regulatable promoter. Under conditions of ZipN depletion, cells progressively enlarged, reflecting restricted cell division, and showed drastic morphological alterations including cell detachment from the filaments, to finish lysing. In contrast to the wild-type localization in midcell Z-rings, FtsZ was found in delocalized aggregates in strain CSL109. Consistently, the proportion of membrane-associated to soluble FtsZ in fractionated cell extracts was lower in CSL109. Bacterial two-hybrid analysis showed that ZipN interacts with FtsZ and other cell-division proteins including cytoplasmic Ftn6 and SepF, and polytopic FtsW, FtsX, FtsQ and FtsI. Additionally, ZipN interacted with the septal protein SepJ, and in CSL109 depletion of ZipN was concomitant with a progressive loss of septal specificity of SepJ. Thus, in Anabaena ZipN represents an essential FtsZ membrane tether and an organizer of the divisome, and it contributes to the conformation of septal structures for filament integrity and intercellular communication.
异形胞形成蓝藻的有机体细胞单位是由隔膜连接的沟通细胞丝，由桥接相邻细胞细胞质的蛋白质结构组成。这种独特的细菌组织在细胞分裂过程中得以保留。在鱼腥藻中，zipN 基因的缺失不能被分离。我们生成了表达合成可调控启动子 zipN 的 CSL109 菌株。在 ZipN 耗尽的条件下，细胞逐渐增大，反映出细胞分裂受限，并显示出剧烈的形态改变，包括从丝状体上脱离，最终裂解。与野生型在中细胞 Z 环中的定位相比，FtsZ 在 CSL109 中被发现存在于定位不定的聚集体中。一致地，在 CSL109 中，膜相关可溶性 FtsZ 在分级细胞提取物中的比例较低。细菌双杂交分析表明，ZipN 与 FtsZ 以及其他细胞分裂蛋白相互作用，包括细胞质 Ftn6 和 SepF，以及多拓扑结构的 FtsW、FtsX、FtsQ 和 FtsI。此外，ZipN 与隔膜蛋白 SepJ 相互作用，在 CSL109 中 ZipN 的耗竭伴随着 SepJ 隔膜特异性的逐渐丧失。因此，在鱼腥藻中，ZipN 代表了必需的 FtsZ 膜系绳和分裂体的组织者，它有助于隔膜结构的构象完整性和细胞间通讯。
