Inactivation of the extracytoplasmic function sigma factor Sig6 stimulates avermectin production in Streptomyces
Libin Jiang1, Yanping Liu, Pan Wang
1State Key Laboratories for Agro-biotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, People's Republic of China. jianglibin1984@163.com
Abstract:
The role of the extracytoplasmic function (ECF) σ factor Sig6 (SAV663) in avermectin production by Streptomyces avermitilis was investigated by gene-deletion, complementation and over-expression experiments. Inactivation of Sig6 had no major effect on growth, stress responses, or morphology. Avermectin yield was increased 2- to 2.7-fold (~680 μg/ml) relative to the wild-type strain by deletion of the sig6 gene, and was restored to the wild-type level by introduction of a single copy of sig6. Introduction of extra multi-copy or integrative sig6 vectors into the wild-type decreased avermectin yield by 56-63%. Taken together, these findings indicate that Sig6 plays a negative regulatory role in avermectin production in S. avermitilis. RT-PCR analysis demonstrated that this role of Sig6 is mediated by the pathway-specific activator gene aveR.
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