ppGpp Metabolism Is Involved in Heterocyst Development in the Cyanobacterium Anabaena sp. Strain PCC 7120
ppGpp Metabolism Is Involved in Heterocyst Development in the Cyanobacterium Anabaena sp. Strain PCC 7120
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DOI：
10.1128/jb.00724-13
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发表时间：
2013-08
影响因子：
3.2
通讯作者：
Shaojuan Zhang;G. Lin;Wen-Li Chen;Li Wang;Cheng‐Cai Zhang
中科院分区：
文献类型：
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作者：
Shaojuan Zhang;G. Lin;Wen-Li Chen;Li Wang;Cheng‐Cai Zhang
摘要丝状蓝藻Anabaena sp. PCC 7120（Anabaena）在缺乏结合氮源的条件下，可以形成具有固氮能力的异形胞。异形胞的分化过程大约需要20到24小时，在此期间发生广泛的代谢和形态变化。鸟苷四磷酸（ppGpp）是严格应答的信号，其通过响应细菌中的营养饥饿调节主要细胞活性来确保细胞存活，并且ppGpp在异形胞分化的早期阶段积累（J. Akinyanju，R. J. Smith，FEBS Lett. 107：173-176，1979; J Akinyanju，R. J. Smith，New Phytol。105：117-122，1987）。在这里，我们表明，所有1549（在这里指定relana）鱼腥藻，同源relA/spoT，上调响应氮剥夺和主要定位在营养细胞。破坏relana强烈影响ppGpp的合成，并且所产生的突变体all 1549 Ωsp/sm不能形成异形胞，并且在缺乏结合氮源的情况下不能生长。这种表型可以通过relana的野生型拷贝来补充。虽然hetR的上调在突变体中受到影响，但hetR的异位过表达不能挽救表型。然而，我们发现，突变体迅速失去其活力，在3至6小时的时间窗口内，结合氮的剥夺。我们建议，ppGpp起着重要的作用，在重新平衡的细胞的代谢活动中的氮源供应的情况下，这种调节是必要的细丝的生存，从而为异形胞分化的成功。
ABSTRACT When deprived of a combined-nitrogen source in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 (Anabaena) can form heterocysts capable of nitrogen fixation. The process of heterocyst differentiation takes about 20 to 24 h, during which extensive metabolic and morphological changes take place. Guanosine tetraphosphate (ppGpp) is the signal of the stringent response that ensures cell survival by adjusting major cellular activities in response to nutrient starvation in bacteria, and ppGpp accumulates at the early stage of heterocyst differentiation (J. Akinyanju, R. J. Smith, FEBS Lett. 107:173–176, 1979; J Akinyanju, R. J. Smith, New Phytol. 105:117–122, 1987). Here we show that all1549 (here designated relana) in Anabaena, homologous to relA/spoT, is upregulated in response to nitrogen deprivation and predominantly localized in vegetative cells. The disruption of relana strongly affects the synthesis of ppGpp, and the resulting mutant, all1549Ωsp/sm, fails to form heterocysts and to grow in the absence of a combined-nitrogen source. This phenotype can be complemented by a wild-type copy of relana. Although the upregulation of hetR is affected in the mutant, ectopic overexpression of hetR cannot rescue the phenotype. However, we found that the mutant rapidly loses its viability, within a time window of 3 to 6 h, following the deprivation of combined nitrogen. We propose that ppGpp plays a major role in rebalancing the metabolic activities of the cells in the absence of the nitrogen source supply and that this regulation is necessary for filament survival and consequently for the success of heterocyst differentiation.