The hetC Gene Is a Direct Target of the NtcA Transcriptional Regulator in Cyanobacterial Heterocyst Development
The hetC Gene Is a Direct Target of the NtcA Transcriptional Regulator in Cyanobacterial Heterocyst Development
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DOI：
10.1128/jb.181.21.6664-6669.1999
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发表时间：
1999-11
影响因子：
3.2
通讯作者：
A. Muro-Pastor;A. Valladares;E. Flores;A. Herrero
中科院分区：
文献类型：
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作者：
A. Muro-Pastor;A. Valladares;E. Flores;A. Herrero
摘要异形胞是某些丝状蓝藻需氧培养物中的固氮部位。鱼腥藻菌株PCC 7120的异形胞发育依赖于全局氮调节因子NtcA，并且需要hetR和hetC基因的产物等。通过RNA-DNA杂交检测，ntcA突变体中hetC的表达受损.相对于hetC翻译起点，氮调节的、NtcA依赖的推定转录起点位于核苷酸-571处。该转录起始点上游的序列显示出由NtcA激活的典型蓝藻启动子的结构，并且纯化的NtcA蛋白特异性地结合到含有该启动子的DNA片段。因此，在异型胞发育过程中hetC表达的激活似乎直接由NtcA操作。NtcA介导的hetR表达的激活在hetC突变体中没有受损，表明HetC不是hetR诱导所需的NtcA依赖性元件。
ABSTRACT The heterocyst is the site of nitrogen fixation in aerobically grown cultures of some filamentous cyanobacteria. Heterocyst development in Anabaena sp. strain PCC 7120 is dependent on the global nitrogen regulator NtcA and requires, among others, the products of the hetR and hetC genes. Expression of hetC, tested by RNA- DNA hybridization, was impaired in an ntcA mutant. A nitrogen-regulated, NtcA-dependent putative transcription start point was localized at nucleotide −571 with respect to the hetC translational start. Sequences upstream from this transcription start point exhibit the structure of the canonical cyanobacterial promoter activated by NtcA, and purified NtcA protein specifically bound to a DNA fragment containing this promoter. Activation of expression of hetC during heterocyst development appears thus to be directly operated by NtcA. NtcA-mediated activation of hetR expression was not impaired in a hetC mutant, indicating that HetC is not an NtcA-dependent element required for hetR induction.