On October 18, 2022, Deng Xin’s research group of City University of Hong Kong published a paper in Cell Reports, revealing the elastic regulation function of two-component system networks in Pseudomonas syringae, and providing a reference and basis for the study of elastic regulation of two-component systems in other species.
Signaling molecules from the environment and the host are extremely important for pathogenic bacteria to establish infection in the host. Widely present in microbial and plant cells, two-component systems (TCS) as important signal receptors can sense a variety of signals (including pH, osmotic pressure, light signal, temperature, small molecules, etc.) to regulate life activities in cells. Two-component systems typically consist of a signal-sensing histidine kinase and a response regulator adjacent to it. Histidine kinases perform autophosphorylation on their histidine residues after sensing external signals, and after self-phosphorylation, phosphate groups are transferred to the arginine residues of their adjacent reaction regulators, thereby regulating the expression of downstream genes in the two-component system.
Pseudomonas syringae is the causative agent of bacterial spot disease in many major crops and fruits around the world, and due to its invasion of infection, resulting in reduced yields, Pseudomonas syringae is a great threat to food security worldwide. Pseudomonas syringa mainly relies on the type III secretion system (T3SS) to infect the host, and previous studies have shown that the expression of the type III gene in Pseudomonas syloves is upregulated during host infection and under nutrient deficiency conditions (such as mineral medium, MM), but in a high pH, osmolal, and nutrient-rich environment (King’s B medium, KB). Type 3 gene expression is greatly inhibited. Based on the previous study that the expression of type III genes is largely regulated by the two-component system, Deng Xin’s group and collaborators have long focused on the regulatory system related to the expression of pseudomonas virulence genes, and have now identified a series of important two-component systems or transcription factors and molecular mechanisms (Nature Communications 2019, 2020; Cell Reports 2021; EMBO Reports 2021; eLife 2021; mBio 2019a, 2019b, 2020, 2022; Nucleic Acids Research 2014, 2015; Cell & Bioscience 2022; Environmental Microbiology 2019, 2020）。
As the largest type of signal transduction system in organisms, although the two-component system plays an important role as a signal receptor in the process of maintaining life activities and generating virulence, at the level of the entire two-component system in the cell, how the two-component system network in organisms can achieve regulatory diversity, conservation and synergy at the whole gene level by sensing different external signals has not been carefully studied.
In this paper, Deng Xin’s research group of City University of Hong Kong selected the plant model pathogen Pseudomonas syringa as the research object, and analyzed and verified the transcriptome library sequencing data (RNA-seq) and chromatin immunoprecipitation library sequencing data (ChIP-seq) of all RR cells in Pseudomonas syringae cells, revealing the mechanism of two-component system network elasticity regulating gene expression in different environments. For example, the FimS/AlgR is a typical elastically regulated two-component system. In KB, the carbon metabolism system and the chemical signaling system are positively regulated by it; But in MM, the quorum sensing system is normalized by it. This regulatory model illustrates the important biological function of elastic regulation of two-component systems in bacteria.
Two-component system network resilience regulation mechanism mode
In this study, the authors established a two-component system network in bacteria based on the conservation and variability of bacterial gene expression by environmental changes, which revealed that Pseudomonas syringae was directly regulated in nutrient-rich medium (KB) and nutrient-poor medium (MM), with 232 and 297 genes in two different media, respectively. At the same time, seven TCS were involved in the regulation of multiple virulence pathways: ErcS, Dcsbis, PhoBR and CzcSR regulated T3SS; KinB/AlgB, MerS and PhoBR regulate the extracellular polysaccharide synthesis system; KinB/AlgB, MerS and CopRS regulate the motor system.
Professor Deng Xin from the Department of Biomedical Sciences, City University of Hong Kong is the corresponding author of this paper, which is mainly co-authored by Dr. Xie Yingpeng of Deng Xin’s research group of the Department of Biomedical Sciences, City University of Hong Kong, and doctoral students Li Jingwei and Ding Yiqing. Dr. Shao Xiaolong, PhD student Yue Sun, Professor Shaojun Tang of the Hong Kong University of Science and Technology, and PhD students Xie Fangzhou and Liu Shiyi participated in some of the work. The work was supported by the National Natural Science Foundation of China and the University of Hong Kong Education Grants Committee. (Source: Web of Science)
Related Paper Information:https://doi.org/10.1016/j.celrep.2022.111502
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