负调节基因nsdA在链霉菌中同源性及激活沉默抗生素合成基因簇的研究

nsdA基因是在天蓝色链霉菌中发现的抗生素合成负调控基因。以nsdA基因片段为探针,通过Southern杂交发现nsdA存在于多种链霉菌中。根据天蓝色链霉菌和阿维链霉菌的nsdA序列设计PCR引物,扩增多种链霉菌中nsdA基因并测序。发现在不同链霉菌中nsdA基因的相似性高达77%~100%。其中变铅青链霉菌与天蓝色链霉菌A3(2)的nsdA序列100%一致。变铅青链霉菌通常不合成放线紫红素,中断nsdA获得的突变菌株WQ2能够合成放线紫红素;在WQ2中重新引入野生型nsdA,又失去产抗生素能力。表明nsdA的中断可以激活变铅青链霉菌中沉默的放线紫红素生物合成基因簇的表达;nsdA的广泛存在及其序列高度保守则提示可以尝试用于这些菌种的抗生素高产育种。

Activation of Silent Antibiotic Synthesis in Streptomyces lividans by Disruption of a Negative Regulator nsdA, a Gene Conserved in Streptomyces

The global regulatory gene,nsdA,negatively regulates antibiotics production in Streptomyces coelicolor. Southern blot experiment,using an nsdA fragment of S. coelicolor as probe,indicated that nsdA gene existed in many Streptomyces. Primers were designed based on the published sequences of S. coelicolor and S. avermitilis. PCR amplification and sequencing showed that nsdA in Streptomyces was conservative and that of S. lividans ZX64 has a 100% identity in the nucleotide sequence comparing with that of S. coelicolor A3 (2). The nsdA disrupted mutant of S. lividans was constructed named as WQ2. WQ2 was able to produce actinorhodin but the wild-type strain ZX64 did not,which has a silent gene cluster contributing to the biosynthesis of actinorhodin. However,the ability was lost when another copy of the wild nsdA gene was introduced into WQ2. All the results above indicate that nsdA homologous gene is wildly existent and conserved in Streptomyces. And it plays a role in negatively regulating the actinorhodin synthesis in S. lividans and disruption of it can activate the silent gene cluster.