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首页> 外文期刊>Journal of bacteriology >ATP-Binding Cassette Transport System Involved in Regulation of Morphological Differentiation in Response to Glucose in Streptomyces griseus
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ATP-Binding Cassette Transport System Involved in Regulation of Morphological Differentiation in Response to Glucose in Streptomyces griseus

机译：ATP结合盒式运输系统参与对灰链霉菌葡萄糖反应中形态差异的调控

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Streptomyces griseus NP4, which was derived by UV mutagenesis from strain IFO13350, showed a bald and wrinkled colony morphology in response to glucose. Mutant NP4 formed ectopic septa at intervals along substrate hyphae, and each of the compartments developed into a spore which was indistinguishable from an aerial spore in size, shape, and thickness of the spore wall and in susceptibility to lysozyme and heat. The ectopic spores of NP4 formed in liquid medium differed from “submerged spores” in lysozyme sensitivity. Shotgun cloning experiments with a library of the chromosomal DNA of the parental strain and mutant NP4 as the host gave rise to DNA fragments giving two different phenotypes; one complementing the bald phenotype of the host, and the other causing much severe wrinkled morphology in the host. Subcloning identified a gene (dasR) encoding a transcriptional repressor belonging to the GntR family that was responsible for the reversal of the bald phenotype and a gene (dasA) encoding a lipoprotein probably serving as a substrate-binding protein in an ATP-binding cassette (ABC) transport system that was responsible for the severe wrinkled morphology. These genes were adjacent but divergently encoded. Two genes, named dasB and dasC, encoding a membrane-spanning protein were present downstream of dasA, which suggested that dasRABC comprises a gene cluster for an ABC transporter, probably for sugar import. dasR was transcribed actively during vegetative growth, and dasA was transcribed just after commencement of aerial hypha formation and during sporulation, indicating that both were developmentally regulated. Transcriptional analysis and direct sequencing of dasRA in mutant NP4 suggested a defect of this mutant in the regulatory system to control the expression of these genes. Introduction of multicopies of dasA into the wild-type strain caused ectopic septation in very young substrate hyphae after only 1 day of growth and subsequent sporulation in response to glucose. The ectopic spores of the wild type had a thinner wall than those of mutant NP4, in agreement with the observation that the former was sensitive to lysozyme and heat. Disruption of the chromosomal dasA or dasR in the wild-type strain resulted in growth as substrate mycelium, suggesting an additional role of these genes in aerial mycelium formation. The ectopic septation and sporulation in mutant NP4 and the wild-type strain carrying multicopies of dasA were independent of a microbial hormone, A-factor (2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone), that acts as a master switch of aerial mycelium formation and secondary metabolism.
机译：通过紫外线诱变从菌株IFO13350衍生出的灰链霉菌 NP4，表现出对葡萄糖的秃头和皱纹菌落形态。突变的NP4沿底物菌丝间隔形成异位间隔，每个隔室发育成孢子，在大小，形状和壁厚以及对溶菌酶和热的敏感性方面，它与气生孢子没有区别。在液体培养基中形成的NP4异位孢子与溶菌酶敏感性不同于“淹没孢子”。用亲本菌株的染色体DNA文库和突变体NP4作为宿主的弹枪克隆实验产生了产生两种不同表型的DNA片段。一种补充宿主的秃头表型，另一种引起宿主严重的皱纹形态。亚克隆鉴定了一个编码属于GntR家族的转录阻遏物的基因（ dasR ），该转录阻遏物负责秃头表型的逆转，而一个编码脂蛋白的基因（ dasA ）可能是脂蛋白在ATP结合盒（ABC）转运系统中充当底物结合蛋白，导致严重的皱纹形态。这些基因是相邻的但发散编码。在 dasA 的下游存在两个编码跨膜蛋白的基因，分别是 dasB 和 dasC ，这表明 dasRABC 包含ABC转运蛋白的基因簇，可能是糖的进口。营养生长期间， dasR 会被主动转录，而气生菌丝形成后和孢子形成过程中， dasA 则被转录，表明两者均受发育调节。转录分析和 dasRA NP4突变体的直接测序表明该突变体在调控系统中无法控制这些基因的表达。在野生型菌株中引入 dasA 的多份副本仅在生长1天后就对非常年轻的底物菌丝引起了异位分隔，随后对葡萄糖的反应形成了孢子。野生型异位孢子的壁比突变体NP4的壁薄，这与观察到的前者对溶菌酶和热敏感有关。野生型菌株中染色体 dasA 或 dasR 的破坏导致其作为底物菌丝体生长，表明这些基因在气生菌丝体形成中的额外作用。突变体NP4的异位分离和孢子形成以及带有 dasA 多拷贝的野生型菌株与微生物激素A因子（2-isocapryloyl-3 R -羟甲基-γ-丁内酯），它是气生菌丝形成和次级代谢的主要转换。

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