苏云金芽胞杆菌中Hfq同时调节c-di-GMP与c-di-AMP信号系统的分子机制

RNA伴侣蛋白Hfq是细菌重要的转录后调控因子。c-di-GMP和c-di-AMP均为细菌第二信使分子，统称为c-di-NMP。其胞内水平由相应的代谢酶调控。我们发现苏云金芽胞杆菌中Hfq可同时调控两类c-di-NMP信号通路，其枢纽为调节由营养期到芽胞期的过渡阶段转录因子ScoC，ScoC可同时与c-di-GMP水解酶基因cdgE、cdgF及c-di-AMP水解酶基因gdpP的启动子区结合。本项目拟在苏云金芽胞杆菌中研究ScoC受Hfq及其他转录因子调控后，在过渡阶段调控cdgE、cdgF、gdpP表达，改变胞内c-di-NMP水平，调节细胞生理活性，使细菌平稳进入芽胞期的机制。本项目的实行不仅可揭示Hfq同时调控两种c-di-NMP信号系统的新机制，解析c-di-NMP在过渡阶段的调控功能，丰富Hfq及c-di-NMP信号调控网络，也为有益芽胞杆菌的利用及有害芽胞杆菌的防治提供新思路。

The RNA chaperone protein Hfq is an essential post-transcriptional regulator in bacteria. Both c-di-GMP and c-di-AMP are crucial bacterial nucleoside second messenger molecules, collectively referred to as c-di-NMP. c-di-GMP is synthesized by a diguanylate cyclase with two molecules of GTP as substrate and hydrolyzed by c-di-GMP-specific phosphodiesterases to pGpG or GMP. Similarly, c-di-AMP is produced by a diadenylyl cyclase with two molecules of ATP and hydrolyzed by c-di-AMP-specific phosphodiesterases to either pApA or AMP. In the genome of Bacillus thuringiensis BMB171, there are in total 12 c-di-GMP metabolic enzyme encoding genes for diguanylate cyclase and c-di-GMP-specific phosphodiesterase and six diadenylate cyclase and c-di-AMP-specific phosphodiesterase genes for c-di-AMP metabolisms. c-di-NMP regulates many important physiological functions in bacteria by binding to various target proteins or riboswitches..In our previous work, we found that Hfq knockout strains exhibited many phenotypes similar with c-di-GMP metabolic enzyme knockout strains and c-di-AMP metabolic enzyme knockout strains, suggesting that the physiological functions of Hfq regulation and the physiological functions of c-di-NMP regulation seem to overlap. We thus hypothesize that there is some cross-regulation (or crosstalk) of bacterial metabolism between Hfq and the two types of c-di-NMP in Bacillus thuringiensis, and would like to investigate the underlying mechanism. Through bioinformatics analysis, we found that the binding motif of the transcription factor, ScoC was present in the promoter region of the c-di-GMP-specific phosphodiesterase genes cdgE and cdgF, and c-di-AMP-specific phosphodiesterase gene gdpP. ScoC is a transcriptional factor that regulates the transition from the vegetative phase to the sporulation phase. We wonder whether Hfq can regulate the two types of c-di-NMP signaling pathways at the same time via the hub of ScoC? So, we select Bacillus thuringiensis BMB171 as the model organism. This project thus aims to study how Hfq regulates ScoC in terms of mRNA stability, translation, or protein interaction. At the same time, we also want to explore how ScoC is regulated by Hfq and other transcription factors, and how the expression of cdgE, cdgF, gdpP were regulated in the transitional stage to alter the intracellular c-di-NMP levels to affect the physiological activity of the bacterial cells, leading bacteria to enter the sporulation phase more smoothly..This study shall reveal for the first time a new mechanism by which Hfq regulates both c-di-GMP and c-di-AMP signaling systems, highlights the role of c-di-NMP in the transitional phase, and greatly enriches the regulatory functions of the Hfq, c-di-GMP and c-di-AMP signaling systems. It will provide new ideas for the utilization of beneficial Bacillus, and control of pathogenic Bacillus.