Genes required for aerial growth, cell division, and chromosome segregation are targets of WhiA before sporulation in Streptomyces venezuelae.
Genes required for aerial growth, cell division, and chromosome segregation are targets of WhiA before sporulation in Streptomyces venezuelae.
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DOI：
10.1128/mbio.00684-13
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发表时间：
2013-09-24
期刊：
影响因子：
6.4
通讯作者：
Buttner MJ
中科院分区：
文献类型：
--
作者：
Bush MJ;Bibb MJ;Chandra G;Findlay KC;Buttner MJ
WhiA 是一种非常不寻常的转录调节因子，与真核归巢核酸内切酶家族相关。 WhiA 是丝状细菌链霉菌中孢子形成所必需的，但在革兰氏阳性细菌中也发现了功能未知的 WhiA 同源物。为了更好地了解 WhiA 在链霉菌发育中的作用及其作为转录因子的功能，我们通过染色质免疫沉淀测序 (ChIP-seq) 和微阵列转录分析的结合鉴定了 WhiA 调节子，开发了委内瑞拉链霉菌属的新模式生物，该属在液体培养中形成孢子。调节子包含约 240 个转录单位，WhiA 的激活剂和阻抑剂的功能几乎相同。对完整调节子上游区域的生物信息分析，结合 DNase I 足迹，确定了一个短但高度保守的不对称序列 GACAC，它与大多数 WhiA 靶标相关。无效突变体的构建表明，whiA 是委内瑞拉链霉菌孢子形成分隔和染色体分离启动所必需的，并且发现编码链霉菌细胞分裂机制关键蛋白的几个基因（如 ftsZ、ftsW 和 ftsK）在发育过程中直接被 WhiA 激活。编码在发育中具有重要作用的蛋白质的其他几个基因也被确定为 WhiA 靶标，包括孢子形成特异性 σ 因子 σWhiG 和二鸟苷酸环化酶 CdgB。细胞分裂与产孢细胞中顶端生长的有序停滞紧密协调，filP 编码指导顶端生长的极化体的关键成分，是孢子形成过程中 WhiA 介导的抑制的直接目标。自从最初鉴定了链霉菌发育所需的基因位点以来，所有 bld 和 whi 发育主调节因子均已被克隆和表征，并且在了解驱动形态发生的细胞生物过程方面取得了重大进展。现在的一个主要挑战是通过剖析连接细胞生物过程和发育主调节因子的调节网络来将两者联系起来。最近引入的委内瑞拉链霉菌作为该属的新模型系统，极大地促进了对这些调控网络的研究，该属是一种在液体培养中形成孢子的物种。利用委内瑞拉链球菌，我们表征了直接受这些主调节因子之一 WhiA 控制的基因的调节。我们的结果表明 WhiA 直接调节孢子形成的关键步骤，包括空中生长的停止、细胞分裂的启动和染色体分离。
WhiA is a highly unusual transcriptional regulator related to a family of eukaryotic homing endonucleases. WhiA is required for sporulation in the filamentous bacterium Streptomyces, but WhiA homologues of unknown function are also found throughout the Gram-positive bacteria. To better understand the role of WhiA in Streptomyces development and its function as a transcription factor, we identified the WhiA regulon through a combination of chromatin immunoprecipitation-sequencing (ChIP-seq) and microarray transcriptional profiling, exploiting a new model organism for the genus, Streptomyces venezuelae, which sporulates in liquid culture. The regulon encompasses ~240 transcription units, and WhiA appears to function almost equally as an activator and as a repressor. Bioinformatic analysis of the upstream regions of the complete regulon, combined with DNase I footprinting, identified a short but highly conserved asymmetric sequence, GACAC, associated with the majority of WhiA targets. Construction of a null mutant showed that whiA is required for the initiation of sporulation septation and chromosome segregation in S. venezuelae, and several genes encoding key proteins of the Streptomyces cell division machinery, such as ftsZ, ftsW, and ftsK, were found to be directly activated by WhiA during development. Several other genes encoding proteins with important roles in development were also identified as WhiA targets, including the sporulation-specific sigma factor σWhiG and the diguanylate cyclase CdgB. Cell division is tightly coordinated with the orderly arrest of apical growth in the sporogenic cell, and filP, encoding a key component of the polarisome that directs apical growth, is a direct target for WhiA-mediated repression during sporulation. Since the initial identification of the genetic loci required for Streptomyces development, all of the bld and whi developmental master regulators have been cloned and characterized, and significant progress has been made toward understanding the cell biological processes that drive morphogenesis. A major challenge now is to connect the cell biological processes and the developmental master regulators by dissecting the regulatory networks that link the two. Studies of these regulatory networks have been greatly facilitated by the recent introduction of Streptomyces venezuelae as a new model system for the genus, a species that sporulates in liquid culture. Taking advantage of S. venezuelae, we have characterized the regulon of genes directly under the control of one of these master regulators, WhiA. Our results implicate WhiA in the direct regulation of key steps in sporulation, including the cessation of aerial growth, the initiation of cell division, and chromosome segregation.