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A cytoplasmic chemoreceptor and Reactive Oxygen Species mediate bacterial chemotaxis to copper

ABSTRACT: Chemotaxis is a widespread strategy used by unicellular and multicellular living organisms to maintain their fitness in stressful environments. We previously showed that bacteria can trigger a negative chemotactic response to a copper (Cu)-rich environment. Cu ions toxicity on bacterial cell physiology has been mainly linked to mismetallation events and ROS production, although the precise role of Cu-generated ROS remains largely debated. Here, we found that the cytoplasmic Cu ions content mirrors variations of the extracellular Cu ions concentration and triggers a dose-dependent oxidative stress, which can be abrogated by superoxide dismutase and catalase overexpression. The inhibition of ROS production in the cytoplasm not only improves bacterial growth but also impedes Cu-chemotaxis, indicating that ROS derived from cytoplasmic Cu ions mediate the control of bacterial chemotaxis to Cu. We also identified the Cu chemoreceptor McpR, which binds Cu ions with low affinity, suggesting a labile interaction. In addition, we demonstrate that the cysteine 75 and histidine 99 within the McpR sensor domain are key residues in Cu chemotaxis and Cu coordination. Finally, we discovered that in vitro both Cu(I) and Cu(II) ions modulate McpR conformation in a distinct manner. Overall,our study provides mechanistic insights on a redox-based control of Cu chemotaxis, indicating that the cellular redox status can play a key role in bacterial chemotaxis.

INSTRUMENT(S): timsTOF Pro

ORGANISM(S): Caulobacter Vibrioides Bacteria

SUBMITTER: Marc Dieu

LAB HEAD: Prof. Jean-Yves MATROULE

PROVIDER: PXD044512 | Pride | 2023-09-05

REPOSITORIES: Pride

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Project description:The transition metal copper (Cu) is an essential element for all living organisms. In plants, Cu plays key roles in electron transport chains of chloroplasts and mitochondria, as well as in cell wall metabolism, ethylene perception, molybdenum cofactor synthesis and oxidative stress protection. Because of its physiological importance, suboptimal concentrations of Cu trigger a re-organization of metabolism to economize on Cu, and pronounced Cu deficiency causes severe growth reduction and defects in male fertility. However, when present in excess, Cu can be highly toxic. Therefore, Cu uptake, utilization and cellular concentrations are strictly regulated. A number of components of the Cu-homeostatic network of Arabidopsis have already been identified. However, the mechanisms that control responses of plant gene expression to Cu-deficiency are only partly understood. In Chlamydomonas reinhardtii, the transcription factor Crr1 is required for activating and/or repressing the expression of a number of genes in response to Cu deficiency. This protein contains a plant-specific DNA-binding domain (SBP domain), ankyrin repeats and a C-terminal cysteine-rich region with similarity to a Drosophila metallothionein (MT). In Arabidopsis, there is a family of 16 proteins with SBP domains named SPL family (SBP-like) of which a subset of proteins have been implicated in flowering time control and floral development. Among all of them, AtSPL7 is the most similar to Crr1 (27 % identity), and AtSPL1 (25 % identity), AtSPL12 (24 % identity) and AtSPL14 (23 % identity) share a common protein architecture. The goal of this work was to obtain a complete account of the response of the Arabidopsis thaliana transcriptome to Cu deficiency, as well as to determine the role of AtSPL7 in the transcriptional response to Cu deficiency. For this purpose, three independent experiments were carried out including Col-0 wild-type and spl7-2 mutant plants grown in Cu-sufficient and Cu-deficient hydroponic media, respectively. Root and shoot transcriptomes were established by RNA-Seq for quantitative comparisons. Sampling of root and shoot tissues of wild-type (WT, Col-0) and spl7-2 mutant plants (the mutant is knock-down for the transcription factor SPL7, which plays a key role in the transcriptional regulation of the copper deficiency responses) cultivated hydroponically in a modified Hoagland's solution under Cu-sufficient (control) and Cu-deficient conditions.

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A cytoplasmic chemoreceptor and Reactive Oxygen Species mediate bacterial chemotaxis to copper

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