title: Involvement of Potassium Transport Systems in the Response of Synechocystis PCC 6803 Cyanobacteria to External pH Change, High-Intensity Light Stress and Heavy Metal Stress.
abstract: The unicellular photosynthetic cyanobacterium, able to survive in varying environments, is the only prokaryote that directly converts solar energy and CO2 into organic material and is thus relevant for primary production in many ecosystems. To maintain the intracellular and intrathylakoid ion homeostasis upon different environmental challenges, the concentration of potassium as a major intracellular cation has to be optimized by various K(+)uptake-mediated transport systems. We reveal here the specific and concerted physiological function of three K(+)transporters of the plasma and thylakoid membranes, namely of SynK (K(+)channel), KtrB (Ktr/Trk/HKT) and KdpA (Kdp) in Synechocystis sp. strain PCC 6803, under specific stress conditions. The behavior of the wild type, single, double and triple mutants was compared, revealing that only Synk contributes to heavy metal-induced stress, while only Ktr/Kdp is involved in osmotic and salt stress adaptation. With regards to pH shifts in the external medium, the Kdp/Ktr uptake systems play an important role in the adaptation to acidic pH. Ktr, by affecting the CO2 concentration mechanism via its action on the bicarbonate transporter SbtA, might also be responsible for the observed effects concerning high-light stress and calcification. In the case of illumination with high-intensity light, a synergistic action of Kdr/Ktp and SynK is required in order to avoid oxidative stress and ensure cell viability. In summary, this study dissects, using growth tests, measurement of photosynthetic activity and analysis of ultrastructure, the physiological role of three K(+)transporters in adaptation of the cyanobacteria to various environmental changes.
authors.affiliation: Department of Biology, University of Padova, Padova 35121, Italy Department of Biomedical Sciences, University of Padova, Padova 35121, Italy.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Checchetto
authors.affiliation: Department of Biology, University of Padova, Padova 35121, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Segalla
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sato
authors.affiliation: Department of Biology, University of Padova, Padova 35121, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Bergantino
authors.affiliation: Department of Biology, University of Padova, Padova 35121, Italy ildi@bio.unipd.it.
authors.forename: Ildiko
authors.initials: I
authors.lastname: Szabo
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai, 980-8579 Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Uozumi
mesh_terms: D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000633:toxicity*; D009154:Mutation; D009997:Osmotic Pressure; D010788:Photosynthesis; D011188:Potassium / Q000378:metabolism*; D013312:Stress, Physiological / Q000187:drug effects; D046939:Synechocystis / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; C113206:KtrB protein, Bacteria; D019216:Metals, Heavy; D011188:Potassium; D002118:Calcium
keywords: Cyanobacteria; Light stress; Potassium transport systems; Resistance to heavy metals; pH changes