State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, 100193, People's Republic of China.
Appl Microbiol Biotechnol. 2014 Jan;98(1):399-409. doi: 10.1007/s00253-013-5348-1. Epub 2013 Nov 13.
Avermectins produced by Streptomyces avermitilis are used commercially for broad-spectrum parasite control in medical, veterinary, and agricultural fields. Our previous comparative transcriptome analysis of wild-type strain ATCC31267 vs. avermectin-overproducing strain 76-02-e revealed that the gene SAV151, which encodes a TetR family transcriptional regulator, was downregulated in 76-02-e. In the present study, we investigated the role of SAV151 in avermectin production. Deletion of SAV151 increased avermectin yield ~1-fold in ATCC31267, and this phenotype was complemented by a single copy of SAV151. Overexpression of SAV151 in ATCC31267 reduced avermectin yield by ~70%. RT-PCR analysis showed that the promoting effect of SAV151 deletion on avermectin production was not due to alteration of ave genes at the transcriptional level. SAV151 negatively regulated the transcription of itself and of the adjacent transcriptional unit SAV152-SAV153-SAV154. In chromatin immunoprecipitation and gel shift assays, purified His6-tagged SAV151 protein bound to the bidirectional SAV151-SAV152 promoter region. SAV151 bound to two palindromic sequences in this region and thereby repressed transcription from both directions. Two of the SAV151 target genes, SAV152 (which encodes a putative dehydrogenase) and SAV154 (which encodes a putative hydrolase), had promoting effects on avermectin production. Our findings provide the basis for a strategy to increase avermectin production by controlling SAV151 and its target genes.
阿维链霉菌产生的阿维菌素被商业用于医学、兽医和农业领域的广谱寄生虫控制。我们之前对野生型菌株 ATCC31267 与阿维菌素高产菌株 76-02-e 的比较转录组分析表明，编码 TetR 家族转录调节因子的基因 SAV151 在 76-02-e 中下调。在本研究中，我们研究了 SAV151 在阿维菌素生产中的作用。SAV151 的缺失使 ATCC31267 的阿维菌素产量增加了约 1 倍，并且这种表型可以通过单个 SAV151 拷贝来互补。SAV151 在 ATCC31267 中的过表达使阿维菌素产量降低了约 70%。RT-PCR 分析表明，SAV151 缺失对阿维菌素生产的促进作用不是由于转录水平上 ave 基因的改变。SAV151 负调控自身和相邻转录单元 SAV152-SAV153-SAV154 的转录。在染色质免疫沉淀和凝胶迁移分析中，纯化的 His6 标记的 SAV151 蛋白与双向 SAV151-SAV152 启动子区域结合。SAV151 结合到该区域的两个回文序列上，从而抑制了两个方向的转录。SAV151 的两个靶基因，SAV152（编码一种假定的脱氢酶）和 SAV154（编码一种假定的水解酶），对阿维菌素的生产有促进作用。我们的研究结果为通过控制 SAV151 及其靶基因来增加阿维菌素产量提供了依据。
