State Key Laboratory of Animal Biotech Breeding and College of Biological Sciences, China Agricultural University, Beijing, China.
Microb Biotechnol. 2024 Jan;17(1):e14319. doi: 10.1111/1751-7915.14319. Epub 2023 Nov 20.
Streptomyces species have a complex life cycle and are the producers of ~70% of commercial antibiotics. Global regulators AfsR and AfsS are widespread among Streptomyces and have been identified as key activators of antibiotic production in several species. However, their roles as repressors of antibiotic production are unclear; in particular, nothing is known regarding the regulatory mechanism of AfsS, despite many decades of research, because it has no DNA-binding domain. Here, we demonstrate that AfsR and AfsS negatively regulate avermectin production and morphological development in the industrially important species S. avermitilis. AfsR directly represses ave structural genes (aveA1, aveA4), cluster-situated activator gene aveR, and eight key developmental genes, whereas it directly activates afsS, aco (for autoregulator avenolide biosynthesis), and avaR1 (encoding avenolide receptor). GST pull-down, microscale thermophoresis, co-immunoprecipitation, and chromatin immunoprecipitation-quantitative PCR assays demonstrated that AfsS interacts with AfsR to co-regulate target genes involved in avermectin production and development and that this interaction requires intact AfsS repeated sequences and enhances the binding affinity of AfsR to target promoters. AfsR/AfsS interaction also occurs in model species S. coelicolor and S. roseosporus (producer of daptomycin, a cyclic lipopeptide antibiotic widely used for the treatment of human infections), suggesting that such interaction is conserved in Streptomyces species. The master developmental repressor BldD acts as a direct activator of both afsR and afsS. Deletion of afsR or afsS strongly enhances avermectin production in wild-type and industrial S. avermitilis strains. Our findings demonstrate novel regulatory roles and mechanisms of AfsR and AfsS in Streptomyces and facilitate methods for antibiotic overproduction.
链霉菌具有复杂的生命周期，是~70%商业抗生素的生产者。全球调节剂 AfsR 和 AfsS 在链霉菌中广泛存在，并被确定为几种抗生素生产的关键激活剂。然而，它们作为抗生素生产抑制剂的作用尚不清楚；特别是，尽管已经进行了几十年的研究，但由于没有 DNA 结合域，对于 AfsS 的调节机制仍一无所知。在这里，我们证明 AfsR 和 AfsS 负调控工业上重要的链霉菌物种 S. avermitilis 中阿维菌素的产生和形态发育。AfsR 直接抑制 aver 结构基因（aveA1、aveA4）、簇定位激活基因 aveR 和八个关键发育基因，而直接激活 afsS、aco（用于 autoregulator avenolide 生物合成）和 avaR1（编码 avenolide 受体）。GST 下拉、微尺度热泳、共免疫沉淀和染色质免疫沉淀定量 PCR 实验表明，AfsS 与 AfsR 相互作用，共同调节参与阿维菌素产生和发育的靶基因，这种相互作用需要完整的 AfsS 重复序列，并增强 AfsR 与靶启动子的结合亲和力。AfsR/AfsS 相互作用也发生在模型物种 S. coelicolor 和 S. roseosporus（生产广泛用于人类感染治疗的环脂肽抗生素达托霉素）中，表明这种相互作用在链霉菌中是保守的。主发育抑制剂 BldD 作为 afsR 和 afsS 的直接激活剂。afsR 或 afsS 的缺失强烈增强野生型和工业 S. avermitilis 菌株中阿维菌素的产生。我们的研究结果表明了 AfsR 和 AfsS 在链霉菌中的新的调节作用和机制，并为抗生素的过量生产提供了方法。
