Streptomyces sahachiroi ATCC 33158中Ⅱ型聚酮合酶基因sahA的功能分析

Functional analysis of a type Ⅱ polyketide synthase gene sahA in Streptomyces sahachiroi ATCC 33158

以酮基合酶基因KSa的简并性引物对Streptomyces sahachiroi基因组进行扩增,发现除了已知的阿嗪霉素B生物合成基因簇以外,还存在一个潜在的聚酮合酶(PKS)基因sahA。对sahA编码的氨基酸序列进行同源性比对及进化树分析,结果表明,sahA属于Ⅱ型聚酮合酶基因家族,与合成孢子色素的基因亲缘关系较近。通过单交换中断sahA基因后,链霉菌孢子的颜色由铅灰色变为白色,而产孢时间、孢子的产量以及其抗紫外线的能力都没有变化,对抗生素阿嗪霉素B的产量也没有影响。初步证实这个潜在的Ⅱ型聚酮合酶基因sahA很可能与S.sahachiroi孢子色素的生物合成有关。

A putative polyketide synthase（PKS） gene sahA was found in the Streptomyces sahachiroi genome by PCR using degenerated primers for the ketosynthase alpha（KSα） gene.The phylogenetic tree and blast analysis revealed that sahA was belonged to the type Ⅱ PKS gene family and closely related with the subgroup of spore-pigment biosynthetic PKS genes.Once sahA was disrupted by single crossover,the spores color of Streptomyces turned into white from leaden but the time of spore-forming,quantity of sporulation,UV-resistant ability of spores and azinomycin B production had no change.It demonstrated that the putative type Ⅱ PKS gene sahA might be involved in the biosynthesis of S.sahachiroi spore-pigment.