Nitrogen regulator GlnR controls uptake and utilization of non-phosphotransferase-system carbon sources in actinomycetes

Abstract

The regulatory mechanisms underlying the uptake and utilization of multiple types of carbohydrates in actinomycetes remain poorly understood. In this study, we show that GlnR (central regulator of nitrogen metabolism) serves as a universal regulator of nitrogen metabolism and plays an important, previously unknown role in controlling the transport of non-phosphotransferase-system (PTS) carbon sources in actinomycetes. It was observed that GlnR can directly interact with the promoters of most (13 of 20) carbohydrate ATP-binding cassette (ABC) transporter loci and can activate the transcription of these genes in response to nitrogen availability in industrial, erythromycin-producing Saccharopolyspora erythraea. Deletion of the glnR gene resulted in severe growth retardation under the culture conditions used, with select ABC-transported carbohydrates (maltose, sorbitol, mannitol, cellobiose, trehalose, or mannose) used as the sole carbon source. Furthermore, we found that GlnR-mediated regulation of carbohydrate transport was highly conserved in actinomycetes. These results demonstrate that GlnR serves a role beyond nitrogen metabolism, mediating critical functions in carbon metabolism and crosstalk of nitrogen-and carbon-metabolism pathways in response to the nutritional states of cells. These findings provide insights into the molecular regulation of transport and metabolism of non-PTS carbohydrates and reveal potential applications for the cofermentation of biomass-derived sugars in the production of biofuels and bio-based chemicals.actinomycetes | GlnR | carbon sources utilization | ABC transport system | nitrogen metabolism

GlnR and PhoP Directly Regulate the Transcription of Genes Encoding Starch-Degrading, Amylolytic Enzymes in Saccharopolyspora erythraea

“…The regulation of starch utilization in soil microorganisms is under GlnR and PhoP control, indicating that nitrogen/ phosphate limitation triggers the PhoP-and GlnR-mediated response, resulting in the expression of nitrogen/phosphate-related genes, as well as genes involved in degradation and utilization of starch. Our previous work also found that GlnR exerts a regulatory effect on uptake and utilization of carbon sources in S. erythraea (36) and could influence production of acetyl coenzyme A (acetyl-CoA), as it directly regulated the transcription of three acs genes encoding acetyl-CoA synthetases (unpublished data). Why do nitrogen/phosphate-sensing regulators activate expression of the genes involved in transport and degradation of carbon sources, as well as acetyl-CoA synthesis?…”

“…(C and D) Curves of growth (C) and consumption of starch (D) of wt, ⌬glnR, ⌬glnR::glnR, wt::glnR, and wt::phoP strains grown in balanced Evans medium supplemented with 0.5% starch as the sole carbon source. Samples for growth and starch digestion curve analysis were harvested at nine time points (12,24,36,48,60,72,84,96, and 108 h). Data are representative of those from three independent biological replicates.…”

“…Interestingly, we have previously shown that S. erythraea possesses an extensive cross talk mechanism between PhoP and GlnR that is involved in the global coordination of nitrogen and phosphate metabolism (34,35). Recently, we found that GlnR controlled the transport of nonphosphotransferase system carbon sources by directly activating the transcription of most carbohydrate ABC transporter loci in response to nitrogen starvation in actinobacteria (36). In the present study, we further demonstrated that most starch-degrading enzymes are subject to upregulation by at least two nutrient-sensing regulators, GlnR and PhoP, in response to nitrogen and phosphate starvation in S. erythraea.…”

The pleiotropic transcriptional regulator NlpR contributes to the modulation of nitrogen metabolism, lipogenesis and triacylglycerol accumulation in oleaginous rhodococci

“…In this context, the NlpR protein may be considered as a pleiotropic regulator since it can influence the expression of genes of multiple pathways. A similar behaviour have been reported for several other regulators in actinobacteria (Martín and Liras, ; Allenby et al ., ; Martín et al , ; Rabyk et al ., ; Liao et al ., ). In contrast to local specific regulators, global and pleiotropic regulators often possess more degenerate binding sites which provide them versatility in their binding affinity, as well as the possibility to control a higher number of genes.…”

Direct Involvement of the Master Nitrogen Metabolism Regulator GlnR in Antibiotic Biosynthesis in Streptomyces

“…Recent reports have demonstrated that GlnR directly regulates the uptake and utilization of non-phosphotransferase system carbon sources in S. erythraea. The expression of most (13 of 20) carbohydrate ATP-binding cassette (ABC) transporters was activated by GlnR in response to nitrogen availability (12). Therefore, GlnR-mediated control of carbohydrate transport may be highly conserved among actinomycetes.…”