σBldN, an extracytoplasmic function RNA polymerase sigma factor required for aerial mycelium formation in Streptomyces coelicolor A3(2)
σBldN, an extracytoplasmic function RNA polymerase sigma factor required for aerial mycelium formation in Streptomyces coelicolor A3(2)
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DOI：
10.1128/jb.182.16.4606-4616.2000
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发表时间：
2000-08-01
影响因子：
3.2
通讯作者：
Buttner, MJ
中科院分区：
文献类型：
--
作者：
Bibb, MJ;Molle, V;Buttner, MJ
天蓝色链霉菌的孢子形成突变体呈现白色，因为它们在灰色聚酮化合物孢子色素的合成中有缺陷，并且这种白色（whi）突变体已被用于定义13个孢子形成位点。whiN是在NTG（N-methyl-N '-nitro-N-nitrosoguanidine）诱导的whi菌株（N. J. Ryding等人，J. Bacteriol. 181：5419-5425，1999）由两种突变体R112和R650定义。R650产生频繁的孢子，比野生型的孢子长。相比之下，R112产生长，直，未分化的菌丝，虽然罕见的孢子链观察到，有时表现出高度不规则的隔膜位置。亚克隆和测序表明，whiN编码的RNA聚合酶σ因子的细胞质外功能亚家族的成员，σ因子具有不寻常的N-末端延伸约86个残基，这是不存在于其他σ因子。构建的whiN无效突变体未能形成气生菌丝体（“秃”表型），因此，whiN被重命名为bldN。这一观察结果并非完全出乎意料，因为在某些培养基上，R112点突变体产生的气生菌丝体比其亲本M145少得多。bldN无效突变体不能简单地适应S.天蓝色bid突变体。在野生型和气生菌丝缺陷型bid菌株的菌落发育过程中分析bldN的表达。bldN由单个启动子bldNp转录。bldN转录受到发育调节，大约在气生菌丝形成时开始，并且依赖于bldG和bldH，但不依赖于bldA、bids、bldC、bldF、bldK或bldJ或bldN本身。从pi启动子的反应调节基因bldM的转录依赖于bldN在体内，和bldMp 1启动子被证明是一个直接的生物化学目标，在体外的西格玛（BldN）全酶。
Sporulation mutants of Streptomyces coelicolor appear white because they are defective in the synthesis of the gray polyketide spore pigment, and such white (whi) mutants have been used to define 13 sporulation loci. whiN, one of five new whi loci identified in a recent screen of NTG (N-methyl-N'-nitro-N-nitrosoguanidine)induced whi strains (N. J. Ryding et al., J. Bacteriol. 181:5419-5425, 1999), was defined by two mutants, R112 and R650. R650 produced frequent spores that were longer than those of the wild type. In contrast, R112 produced long, straight, undifferentiated hyphae, although rare spore chains were observed, sometimes showing highly irregular septum placement. Subcloning and sequencing showed that whiN encodes a member of the extracytoplasmic function subfamily of RNA polymerase sigma factors and that the sigma factor has an unusual N-terminal extension of approximately 86 residues that is not present in other sigma factors. A constructed whiN null mutant failed to form aerial mycelium (the "bald" phenotype) and, as a consequence, whiN was renamed bldN. This observation was not totally unexpected because, on some media, the R112 point mutant produced substantially less aerial mycelium than its parent, M145. The bldN null mutant did not fit simply into the extracellular signaling cascade proposed for S. coelicolor bid mutants. Expression of bldN was analyzed during colony development in wild-type and aerial mycelium-deficient bid strains. bldN was transcribed from a single promoter, bldNp. bldN transcription was developmentally regulated, commencing approximately at the time of aerial mycelium formation, and depended on bldG and bldH, but not on bldA, bids, bldC, bldF, bldK, or bldJ or on bldN itself. Transcription from the pi promoter of the response-regulator gene bldM depended on bldN in vivo, and the bldMp1 promoter was shown to be a direct biochemical target for sigma(BldN) holoenzyme in vitro.