BldC delays entry into development to produce a sustained period of vegetative growth in Streptomyces venezuelae
BldC delays entry into development to produce a sustained period of vegetative growth in Streptomyces venezuelae
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BldC 延迟进入开发阶段，以在委内瑞拉链霉菌中产生持续的营养生长期
DOI：
10.1101/194126
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发表时间：
2017
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影响因子：
--
通讯作者：
Bush M
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文献类型：
--
作者：
Bush M
链霉菌是丝状细菌，通过产生称为气生菌丝的孢子生殖结构来分化。从营养生长到生殖生长的转变由bld（bald）位点控制，bld基因的突变通过阻止进入发育（典型地是激活子的突变）或通过诱导营养菌丝体中的早熟孢子形成（典型地是阻遏子的突变）来防止气生菌丝的形成。bldC基因编码一个68个氨基酸残基的DNA结合蛋白，与MerR家族转录因子的DNA结合结构域相关。最近的研究表明BldC通过一种新的机制与DNA结合，但对其对链霉菌发育的影响了解较少。在这里，我们使用ChIP-seq与RNA-seq结合来定义模型物种委内瑞拉链霉菌中的BldC调节子，表明BldC既可以作为转录的阻遏物又可以作为转录的激活物。利用电子显微镜和延时成像，我们发现bldC突变体是秃头的，因为他们过早地启动发展，绕过气生菌丝的形成。这与BldC靶基因的过早表达一致，所述BldC靶基因编码在发育中具有关键作用的蛋白（例如，whiD，whiI，sigF），染色体凝聚和分离（例如，smeA-sffA，hupS）和孢子形成特异性细胞分裂（例如，dynAB），这表明Bldc介导的抑制对于在孢子形成之前维持持续的营养生长期是至关重要的。我们讨论了可能的意义BldC作为MerR家族转录因子和DNA architectural proteins.IMPORTANCEUnderstanding驱动细菌形态发生的机制之间的进化联系依赖于解剖的监管网络，支持所涉及的细胞生物学过程。近年来，委内瑞拉链霉菌（Streptomyces venezuelae）已成为链霉菌形态分化研究的一个有吸引力的模式系统。这导致了在鉴定由调节气生菌丝体形成（Bld调节子）和孢子形成（Whi调节子）的转录因子控制的基因方面的重大进展。利用S。在委内瑞拉，我们使用与RNA-seq偶联的ChIP-seq来鉴定直接受BldC控制的基因。因为。委内瑞拉孢子在液体培养中，完整的孢子到孢子的生命周期可以用延时显微镜检查，我们将这种技术应用于bldC突变体。这些组合的方法揭示BldC是Bld调节剂的新兴类别的成员，其功能主要是抑制关键的孢子形成基因，从而延长营养生长并阻断形态分化的发生。
Streptomycetes are filamentous bacteria that differentiate by producing spore-bearing reproductive structures called aerial hyphae. The transition from vegetative to reproductive growth is controlled by thebld(bald) loci, and mutations inbldgenes prevent the formation of aerial hyphae, either by blocking entry into development (typically mutations in activators) or by inducing precocious sporulation in the vegetative mycelium (typically mutations in repressors). One of thebldgenes,bldC, encodes a 68-residue DNA-binding protein related to the DNA-binding domain of MerR-family transcription factors. Recent work has shown that BldC binds DNA by a novel mechanism, but there is less insight into its impact onStreptomycesdevelopment. Here we used ChIP-seq coupled with RNA-seq to define the BldC regulon in the model species Streptomyces venezuelae, showing that BldC can function both as a repressor and as an activator of transcription. Using electron microscopy and time-lapse imaging, we show thatbldCmutants are bald because they initiate development prematurely, bypassing the formation of aerial hyphae. This is consistent with the premature expression of BldC target genes encoding proteins with key roles in development (e.g.,whiD,whiI,sigF), chromosome condensation and segregation (e.g.,smeA-sffA,hupS), and sporulation-specific cell division (e.g.,dynAB), suggesting that BldC-mediated repression is critical to maintain a sustained period of vegetative growth prior to sporulation. We discuss the possible significance of BldC as an evolutionary link between MerR family transcription factors and DNA architectural proteins.IMPORTANCEUnderstanding the mechanisms that drive bacterial morphogenesis depends on the dissection of the regulatory networks that underpin the cell biological processes involved. Recently, Streptomyces venezuelae has emerged as an attractive model system for the study of morphological differentiation inStreptomyces. This has led to significant progress in identifying the genes controlled by the transcription factors that regulate aerial mycelium formation (Bld regulators) and sporulation (Whi regulators). Taking advantage ofS. venezuelae, we used ChIP-seq coupled with RNA-seq to identify the genes directly under the control of BldC. BecauseS. venezuelaesporulates in liquid culture, the complete spore-to-spore life cycle can be examined using time-lapse microscopy, and we applied this technique to thebldCmutant. These combined approaches reveal BldC to be a member of an emerging class of Bld regulators that function principally to repress key sporulation genes, thereby extending vegetative growth and blocking the onset of morphological differentiation.