A Novel AdpA Homologue Negatively Regulates Morphological Differentiation in Streptomyces xiamenensis 318

Abstract

The pleiotropic transcriptional regulator AdpA positively controls morphological differentiation and regulates secondary metabolism in most Streptomyces species. Streptomyces xiamenensis 318 has a linear chromosome 5.96 Mb in size. How AdpA affects secondary metabolism and morphological differentiation in such a naturally minimized genomic background is unknown. Here, we demonstrated that AdpASx, an AdpA orthologue in S. xiamenensis, negatively regulates cell growth and sporulation and bidirectionally regulates the biosynthesis of xiamenmycin and polycyclic tetramate macrolactams (PTMs) in S. xiamenensis 318. Overexpression of the adpASx gene in S. xiamenensis 318 had negative effects on morphological differentiation and resulted in reduced transcription of putative ssgA, ftsZ, ftsH, amfC, whiB, wblA1, wblA2, wblE, and a gene encoding sporulation-associated protein (sxim_29740), whereas the transcription of putative bldD and bldA genes was upregulated. Overexpression of adpASx led to significantly enhanced production of xiamenmycin but had detrimental effects on the production of PTMs. As expected, the transcriptional level of the xim gene cluster was upregulated, whereas the PTM gene cluster was downregulated. Moreover, AdpASx negatively regulated the transcription of its own gene. Electrophoretic mobility shift assays revealed that AdpASx can bind the promoter regions of structural genes of both the xim and PTM gene clusters as well as to the promoter regions of genes potentially involved in the cell growth and differentiation of S. xiamenensis 318. We report that an AdpA homologue has negative effects on morphological differentiation in S. xiamenensis 318, a finding confirmed when AdpASx was introduced into the heterologous host Streptomyces lividans TK24. IMPORTANCE AdpA is a key regulator of secondary metabolism and morphological differentiation in Streptomyces species. However, AdpA had not been reported to negatively regulate morphological differentiation. Here, we characterized the regulatory role of AdpASx in Streptomyces xiamenensis 318, which has a naturally streamlined genome. In this strain, AdpASx negatively regulated cell growth and morphological differentiation by directly controlling genes associated with these functions. AdpASx also bidirectionally controlled the biosynthesis of xiamenmycin and PTMs by directly regulating their gene clusters rather than through other regulators. Our findings provide additional evidence for the versatility of AdpA in regulating morphological differentiation and secondary metabolism in Streptomyces.

AdpA Positively Regulates Morphological Differentiation and Chloramphenicol Biosynthesis in Streptomyces venezuelae

“…At the transcriptional level, adpA expression is subject to autoregulatory control, as demonstrated in several previous reports ( 17 , 23 , 32 , 33 ). However, the autoregulatory effect that AdpA exerts on its own gene expression seems to differ across Streptomyces species.…”

“…AdpA orthologs are ubiquitously present in the members of genus Streptomyces and play essential roles in their morphological differentiation ( 10 – 16 ). Most of the AdpA orthologs positively regulate morphogenesis, with the exception of that recently reported in Streptomyces xiamenensis ( 17 ). Colonies of Streptomyces mutants devoid of AdpA are characterized by their inability to produce fluffy aerial hyphae on solid media; such mutants were historically described as “bald” ( 18 , 19 ) and are unable to produce spores.…”

AdpAlin, a Pleiotropic Transcriptional Regulator, Is Involved in the Cascade Regulation of Lincomycin Biosynthesis in Streptomyces lincolnensis

“…On the other hand, AdpA has a negative impact on oviedomycin biosynthesis in S. ansochromogenes by repressing the transcription of CSR (Xu et al, 2017). Very recently, it was reported that AdpA from S. xiamenensis 318 negatively regulates morphological differentiation as well as polycyclic tetramate macrolactams (PTMs) production, while positively regulates xiamenmycin production by activating the transcription of two of the structural genes ximA and ximB (Bu et al, 2019). As we can speculate from previous studies, AdpA typically controls the CSR and/or some structural genes in an antibiotic BGC.…”

Combination of atmospheric and room temperature plasma (ARTP) mutagenesis, genome shuffling and dimethyl sulfoxide (DMSO) feeding to improve FK506 production in Streptomyces tsukubaensis

“…Combined with previous research (Mo et al, 2009;Schumacher et al, 2017), the regulatory mechanism of cdgB and c-di-GMP on morphological differentiation and antibiotic synthesis of S.tsukubaensis needs further investigation. Of course, there may also other growth factors and genes associated with morphology (such as whiB and adpA) (Davis et al, 1992;Xuliang et al, 2019) and sporulation (Dongxu et al, 2018), which were not studied in this study. Moreover, it was found that in slant culture and fermentation, high-yielding fusion strains, altered the secondary metabolism, and tacrolimus production was enhanced, also producing a pink pigment, which deserved further analysis.…”