Study of "IQ" perceived signals of plant pathogenic bacteria: kinase activity that activates the RpfC protein.

Bacteria are often thought of as a class of "low-class" single-celled organisms that live in simple ways.
, however, modern microbiology research has changed this misbetation, finding that bacteria have many properties similar to those of advanced organisms.
For example, in signaling cognition, a key issue related to survival and death of life, bacteria not only perceive environmental stimuli, but also use compounds as molecular "languages" for intercellular communication between different bacterial individuals (i.e., population sensing, quorum-sensing), sensing the presence and population size of the same species, so as to communicate with each other in the process of host infection, free survival and adaptation to adversity, and exhibit distinct groups and sociality.
The molecular "language" of known bacteria includes high-serine esters, peptides, ketones, etc., among which, a class of compounds known as "diffusion control factors (DSF)" are jaundice, prosthetic monocytobacteria, malt-narrow monocytobacteria and Bockles bacteria and other dynamic, phytopathic bacteria to communicate between cells signaling substances.
Over the past 30 years, scientists have been analyzing step by step the process and principles by which bacteria perceive DSF signals: in 1991, during a study in the United Kingdom, Tang Jiliang, a professor at Guangxi University, first discovered that plant pathogenic bacteria (wild rape monocytobacteria) were the same as animal pathogenic bacteria, and that the two-component signal transducting system (RpfC-RpfG) was the main control mechanism for regulating pathogenicity; Research by MJ. Daniels, a professor at the research center, and colleagues suggest that RpfC should be a subject that recognizes extracellular DSF signals, but the exact nature of DSF is still unknown; They were found not only as signaling compounds for communication between bacterial individuals, but also as signaling substances for cross-border signaling between bacteria and fungi, bacteria and plants.
although subsequent studies have found proteins that bind to DSF molecules such as RpfR and RpfS, they are both cytocytoproteins that do not look like DSF subjects located on the surface of cells that sense extracellular DSF.
And for RpfC, which has long been speculated by researchers to sense extracellulose DSF signals, because of its complex structure, it is a histase kinase containing five transmeral regions, which is technically difficult to conduct enzymatic analysis and membrane protein-fatty acid interaction studies, so there has been a lack of direct evidence that RpfC is indeed a bacterial-perceived DSF subject.
Qian Wei Research Group of the Institute of Microbiology of the Chinese Academy of Sciences is engaged in the study of the sensory signals of plant pathogenic bacteria, and is dedicated to analyzing how the bacterial two-component signal transducting system (i.e., the "IQ" of bacteria) recognizes host plant and environmental signals.
recently, they successfully assembled full-length RpfC histase kinases into lipid bimolecules or nanodisc to obtain an enzymaticly active protein lipid body, providing an analytical platform for studying RpfC from biochemical levels.
Based on this platform, they used analytical techniques such as microthermal swimming (MST), thermal migration (TSA) and circular spectrometry to demonstrate that DSF molecules were directly integrated into an area of 22 amino acids in the RpfC signal sensing region, activating the kinase activity of the RpfC protein.
Particularly interesting was the discovery that the near-membrane region (juxtamembrane) of RpfC inhibited its own kinase activity when the bacterial population density was low, but when the bacterial population density was high, DSF stimulation removed the inhibition, thereby activating the population sensing signaling path, regulating the expression of bacterial pathogenic factors and the formation of biofilm.
Therefore, the study presents strong evidence from the perspective of enzymatics and biochemistry, not only proves that RpfC is indeed a membrane subject of DSF signal molecules, solves a difficult problem in the study of bacterial intercellular communication, but also establishes a biochemical analysis platform for membrane-fatty acid interaction, which opens a breakthrough for the further study of the regulation function of DSF family signal molecules in cell-to-cell communication, and the development of new antibacterial compounds that can block the process of bacterial group induction.
the results follow the recent discovery by the Qianwei research team that the "IQ" (i.e. two-component signal transducting system) of jaundia is perceived by high salt stress (Wang et al, 2014, Environ Microbiol.16:21) 26-2144), after sensing the iron deficiency environment in the host plant (Wang et al, 2016.PLoS Pathogens.12:e1006133), again made important progress in this area.
results have been published in the journal PLos Pathogens (Cai et al, 2017.Fatty Acid DSF Binds and Allosterically Activates Histidine Kinase RpfC of Phytopathogenic Bacterium Xantonhomas campris pv.campestris Regulation to Quorum-Sensing and Virulence).
, Ph.D. students at the Institute of Microbiology, is the co-first author of the paper.
research has been funded by the Chinese Academy of Sciences strategic pilot science and technology special category B and the National Natural Science Foundation of China.
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