Li Jinyang, Liu Qian, Li Jingen, Lin Liangcai, Li Xiaolin, Zhang Yongli, Tian Chaoguang
Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Biotechnol Biofuels. 2021 Jan 28;14(1):33. doi: 10.1186/s13068-021-01877-2.
Low- and high-affinity glucose transport system is a conserved strategy of microorganism to cope with environmental glucose fluctuation for their growth and competitiveness. In Neurospora crassa, the dual-affinity glucose transport system consists of a low-affinity glucose transporter GLT-1 and two high-affinity glucose transporters HGT-1/HGT-2, which play diverse roles in glucose transport, carbon metabolism, and cellulase expression regulation. However, the regulation of this dual-transporter system in response to environmental glucose fluctuation is not yet clear.
In this study, we report that a regulation module consisting of a downstream transcription factor COL-26 and an upstream non-transporting glucose sensor RCO-3 regulates the dual-affinity glucose transport system in N. crassa. COL-26 directly binds to the promoter regions of glt-1, hgt-1, and hgt-2, whereas RCO-3 is an upstream factor of the module whose deletion mutant resembles the Δcol-26 mutant phenotypically. Transcriptional profiling analysis revealed that Δcol-26 and Δrco-3 mutants had similar transcriptional profiles, and both mutants had impaired response to a glucose gradient. We also showed that the AMP-activated protein kinase (AMPK) complex is involved in regulation of the glucose transporters. AMPK is required for repression of glt-1 expression in starvation conditions by inhibiting the activity of RCO-3.
RCO-3 and COL-26 form an external-to-internal module that regulates the glucose dual-affinity transport system. Transcription factor COL-26 was identified as the key regulator. AMPK was also involved in the regulation of the dual-transporter system. Our findings provide novel insight into the molecular basis of glucose uptake and signaling in filamentous fungi, which may aid in the rational design of fungal strains for industrial purposes.
低亲和力和高亲和力葡萄糖转运系统是微生物应对环境葡萄糖波动以实现生长和竞争的一种保守策略。在粗糙脉孢菌中，双亲和力葡萄糖转运系统由一个低亲和力葡萄糖转运蛋白GLT-1和两个高亲和力葡萄糖转运蛋白HGT-1/HGT-2组成，它们在葡萄糖转运、碳代谢和纤维素酶表达调控中发挥着不同作用。然而，这种双转运蛋白系统对环境葡萄糖波动的响应调控尚不清楚。
在本研究中，我们报道了一个由下游转录因子COL-26和上游非转运葡萄糖传感器RCO-3组成的调控模块，该模块调控粗糙脉孢菌中的双亲和力葡萄糖转运系统。COL-26直接结合到glt-1、hgt-1和hgt-2的启动子区域，而RCO-3是该模块的上游因子，其缺失突变体在表型上类似于Δcol-26突变体。转录谱分析表明，Δcol-26和Δrco-3突变体具有相似的转录谱，且两个突变体对葡萄糖梯度的响应均受损。我们还表明，AMP激活的蛋白激酶（AMPK）复合物参与葡萄糖转运蛋白的调控。在饥饿条件下，AMPK通过抑制RCO-3的活性来抑制glt-1的表达。
RCO-3和COL-26形成一个从外部到内部的模块，调控葡萄糖双亲和力转运系统。转录因子COL-26被确定为关键调控因子。AMPK也参与双转运蛋白系统的调控。我们的研究结果为丝状真菌中葡萄糖摄取和信号传导的分子基础提供了新的见解，这可能有助于合理设计用于工业目的的真菌菌株。
