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首页> 外文期刊>Applied Microbiology >GlnR and PhoP Directly Regulate the Transcription of Genes Encoding Starch-Degrading, Amylolytic Enzymes in Saccharopolyspora erythraea
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GlnR and PhoP Directly Regulate the Transcription of Genes Encoding Starch-Degrading, Amylolytic Enzymes in Saccharopolyspora erythraea

机译：GlnR和PhoP直接调节糖多孢红霉中淀粉降解，淀粉分解酶编码基因的转录。

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Starch-degrading enzymes hydrolyze starch- and starch-derived oligosaccharides to yield glucose. We investigated the transcriptional regulation of genes encoding starch-degrading enzymes in the industrial actinobacterium Saccharopolyspora erythraea . We observed that most genes encoding amylolytic enzymes (one α-amylase, one glucoamylase, and four α-glucosidases) were regulated by GlnR and PhoP, which are global regulators of nitrogen and phosphate metabolism, respectively. Electrophoretic mobility shift assays and reverse transcription-PCR (RT-PCR) analyses demonstrated that GlnR and PhoP directly interact with their promoter regions and collaboratively or competitively activate their transcription. Deletion of glnR caused poor growth on starch, maltodextrin, and maltose, whereas overexpression of glnR and phoP increased the total activity of α-glucosidase, resulting in enhanced carbohydrate utilization. Additionally, transcript levels of amylolytic genes and total glucosidase activity were induced in response to nitrogen and phosphate limitation. Furthermore, regulatory effects of GlnR and PhoP on starch-degrading enzymes were conserved in Streptomyces coelicolor A3(2). These results demonstrate that GlnR and PhoP are involved in polysaccharide degradation by mediating the interplay among carbon, nitrogen, and phosphate metabolism in response to cellular nutritional states. Our study reveals a novel regulatory mechanism underlying carbohydrate metabolism, and suggests new possibilities for designing genetic engineering approaches to improve the rate of utilization of starch in actinobacteria.IMPORTANCE The development of efficient strategies for utilization of biomass-derived sugars, such as starch and cellulose, remains a major technical challenge due to the weak activity of associated enzymes. Here, we found that GlnR and PhoP directly regulate the transcription of genes encoding amylolytic enzymes and present insights into the regulatory mechanisms of degradation and utilization of starch in actinobacteria. Two nutrient-sensing regulators may play important roles in creating a direct association between nitrogen/phosphate metabolisms and carbohydrate utilization, as well as modulate the C:N:P balance in response to cellular nutritional states. These findings highlight the interesting possibilities for designing genetic engineering approaches and optimizing the fermentation process to improve the utilization efficiency of sugars in actinobacteria via overexpression of the glnR and phoP genes and nutrient signal stimulation.
机译：淀粉降解酶水解淀粉和淀粉衍生的寡糖以产生葡萄糖。我们研究了在工业放线放线菌Saccharopolyspora erythraea中编码淀粉降解酶的基因的转录调控。我们观察到，大多数编码淀粉分解酶的基因（一种α-淀粉酶，一种葡糖淀粉酶和四种α-葡萄糖苷酶）均受GlnR和PhoP的调节，它们分别是氮和磷酸盐代谢的全局调节剂。电泳迁移率变动分析和逆转录PCR（RT-PCR）分析表明，GlnR和PhoP直接与其启动子区域相互作用，并协同或竞争性地激活其转录。 glnR的缺失导致淀粉，麦芽糊精和麦芽糖的生长不良，而glnR和phoP的过表达增加了α-葡萄糖苷酶的总活性，从而提高了碳水化合物的利用率。另外，响应于氮和磷酸盐的限制，诱导了淀粉分解基因的转录水平和总葡糖苷酶活性。此外，GlnR和PhoP对淀粉降解酶的调节作用在链霉菌A3（2）中得以保留。这些结果表明，GlnR和PhoP通过介导响应细胞营养状态的碳，氮和磷酸盐代谢之间的相互作用而参与多糖降解。我们的研究揭示了碳水化合物代谢的新调控机制，并为设计基因工程方法以提高放线菌中淀粉利用率的可能性提供了新的可能性。重要的是利用生物质衍生糖（例如淀粉和纤维素）的有效策略的发展由于相关酶的活性较弱，因此仍然是主要的技术挑战。在这里，我们发现GlnR和PhoP直接调节编码淀粉分解酶的基因的转录，并提出对放线菌中淀粉降解和利用的调节机制的见解。在建立氮/磷酸盐代谢与碳水化合物利用之间的直接联系以及调节C：N：P平衡以响应细胞营养状态方面，两种营养敏感调节剂可能发挥重要作用。这些发现凸显了设计基因工程方法和优化发酵过程以通过过度表达glnR和phoP基因以及营养信号刺激来提高放线菌中糖的利用效率的有趣可能性。

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