A partner-switching regulatory system controls hormogonium development in the filamentous cyanobacterium Nostoc punctiforme
A partner-switching regulatory system controls hormogonium development in the filamentous cyanobacterium Nostoc punctiforme
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DOI：
10.1111/mmi.14061
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发表时间：
2018-08-01
影响因子：
3.6
通讯作者：
Risser, Douglas D.
中科院分区：
文献类型：
--
作者：
Riley, Kelsey W.;Gonzalez, Alfonso;Risser, Douglas D.
丝状蓝藻具有发育的复杂性，包括在许多物种的运动藻殖体的短暂分化。使用正向遗传学方法，一个三人组的基因独特的丝状蓝藻编码一个假定的RSB样的合作伙伴转换调节系统（PSRS）涉及在调节藻殖体的发展模式丝状蓝藻Nostoc点状念珠藻。框内缺失菌株的分析表明，HmpU（推定的丝氨酸磷酸酶）和HmpV（STAS结构域）增强，而HmpW（推定的丝氨酸激酶）抑制运动和持久性的Hormogonium状态。蛋白质-蛋白质相互作用研究证明了HmpW和HmpV之间的特异性。hmpW和hmpV之间的上位性分析与HmpV作为系统的下游效应物而不是由HmpW调节σ因子一致。缺失hmpU或hmpV减少细胞外PilA和藻殖子多糖（HPS）的积累，IV型菌毛和HPS特异性基因的表达在hmpV菌株中减少。Hmp PSRS的表达在藻殖子中被诱导，并且HmpV-GFPuv的细胞质定位意味着其下游靶标也可能是细胞质。总的来说，这些结果支持HmpU和HmpW拮抗调节HmpV的磷酸化状态的模型，随后，未磷酸化的HmpV正调节不确定的下游靶点，以影响Hormogonium特异性基因表达。
Filamentous cyanobacteria exhibit developmental complexity, including the transient differentiation of motile hormogonia in many species. Using a forward genetic approach, a trio of genes unique to filamentous cyanobacteria encoding a putative Rsb-like partner-switching regulatory system (PSRS) was implicated in regulating hormogonium development in the model filamentous cyanobacterium Nostoc punctiforme. Analysis of in-frame deletion strains indicated that HmpU (putative serine phosphatase) and HmpV (STAS domain) enhance, while HmpW (putative serine kinase) represses motility and persistence of the hormogonium state. Protein-protein interaction studies demonstrated specificity between HmpW and HmpV. Epistasis analysis between hmpW and hmpV was consistent with HmpV acting as the downstream effector of the system, rather than regulation of a sigma factor by HmpW. Deletion of hmpU or hmpV reduced accumulation of extracellular PilA and hormogonium polysaccharide (HPS), and expression of type IV pilus- and HPS-specific genes was reduced in the hmpV strain. Expression of the Hmp PSRS is induced in hormogonia, and the cytoplasmic localization of HmpV-GFPuv implies that its downstream target is probably cytoplasmic as well. Collectively, these results support a model where HmpU and HmpW antagonistically regulate the phosphorylation state of HmpV, and subsequently, unphosphorylated HmpV positively regulates an undefined downstream target to affect hormogonium-specific gene expression.