Transcription of the sporulation gene ssgA is activated by the IclR-type regulator SsgR in a whi-independent manner in Streptomyces coelicolor A3(2)
Transcription of the sporulation gene ssgA is activated by the IclR-type regulator SsgR in a whi-independent manner in Streptomyces coelicolor A3(2)
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DOI：
10.1111/j.1365-2958.2004.04186.x
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发表时间：
2004-08-01
影响因子：
3.6
通讯作者：
van Wezel, GP
中科院分区：
文献类型：
--
作者：
Traag, BA;Kelemen, GH;van Wezel, GP
SSgA在控制链霉菌产孢特异性细胞分裂和形态发生中起着重要作用，SSgA缺失突变体具有罕见的条件性非产孢表型。在本文中，我们证明了天蓝色链霉菌中SSgA和位于上游的ICLR型调控基因SSgR的转录在发育过程中受到调控，并在孢子形成开始时被激活。构建的SSgR零突变体的表型与SSgA突变体非常相似。该突变体缺乏SSgA转录可能是其产孢量不足的唯一原因，因为野生型产孢量可以通过Erme启动子上不依赖于SsgR的SSgA表达来恢复。SsgR的一个截短版本与SSgA启动子区域的结合表明，SSgA转录是由SsgR直接激活的；天蓝色链霉菌中SSgA对SsgR的这种依赖与灰色链霉菌的情况形成鲜明对比，在灰色链霉菌中，SSgA转录由A因子激活，其受SsgR同源基因SsfR的控制远没有那么重要。我们未能用灰链霉菌ssfR来补充ssgR突变体，这表明两个基因之间存在功能差异。这些观察结果可能解释了天蓝色链球菌和灰链球菌在发育控制方面的一些重大差异，这在最近的一次微观审查中得到了强调(Chater和Horinouchi(2003)Mol Microbiol 48：9-15)。令人惊讶的是，SSgA和SSgR的转录不依赖于早期的Whi基因(WhiA、WhiB、WHIG、Whih、WhiI和WhiJ)。
SsgA plays an important role in the control of sporulation-specific cell division and morphogenesis of streptomycetes, and ssgA null mutants have a rare conditionally non-sporulating phenotype. In this paper we show that transcription of ssgA and of the upstream-located ssgR, an iclR-type regulatory gene, is developmentally regulated in Streptomyces coelicolor and activated towards the onset of sporulation. A constructed ssgR null mutant was phenotypically very similar to the ssgA mutant. The absence of ssgA transcription in this mutant is probably the sole cause of its sporulation deficiency, as wild-type levels of sporulation could be restored by the SsgR-independent expression of ssgA from the ermE promoter. Binding of a truncated version of SsgR to the ssgA promoter region showed that ssgA transcription is directly activated by SsgR; such a dependence of ssgA on SsgR in S. coelicolor is in clear contrast to the situation in S. griseus, where ssgA transcription is activated by A-factor, and its control by the SsgR orthologue, SsfR, is far less important. Our failure to complement the ssgR mutant with S. griseus ssfR suggests functional differences between the genes. These observations may explain some of the major differences in developmental control between the phylogenetically divergent species S. coelicolor and S. griseus, highlighted in a recent microreview (Chater and Horinouchi (2003) Mol Microbiol 48: 9-15). Surprisingly, transcription of ssgA and ssgR is not dependent on the early whi genes (whiA, whiB, whiG, whiH, whiI and whiJ ).