title: Plasma membrane aquaporin AqpZ protein is essential for glucose metabolism during photomixotrophic growth of Synechocystis sp. PCC 6803.
abstract: The genome of Synechocystis PCC 6803 contains a single gene encoding an aquaporin, aqpZ. The AqpZ protein functioned as a water-permeable channel in the plasma membrane. However, the physiological importance of AqpZ in Synechocystis remains unclear. We found that growth in glucose-containing medium inhibited proper division of ΔaqpZ cells and led to cell death. Deletion of a gene encoding a glucose transporter in the ΔaqpZ background alleviated the glucose-mediated growth inhibition of the ΔaqpZ cells. The ΔaqpZ cells swelled more than the wild type after the addition of glucose, suggesting an increase in cytosolic osmolarity. This was accompanied by a down-regulation of the pentose phosphate pathway and concurrent glycogen accumulation. Metabolite profiling by GC/TOF-MS of wild-type and ΔaqpZ cells revealed a relative decrease of intermediates of the tricarboxylic acid cycle and certain amino acids in the mutant. The changed levels of metabolites may have been the cause for the observed decrease in growth rate of the ΔaqpZ cells along with decreased PSII activity at pH values ranging from 7.5 to 8.5. A mutant in sll1961, encoding a putative transcription factor, and a Δhik31 mutant, lacking a putative glucose-sensing kinase, both exhibited higher glucose sensitivity than the ΔaqpZ cells. Examination of protein expression indicated that sll1961 functioned as a positive regulator of aqpZ gene expression but not as the only regulator. Overall, the ΔaqpZ cells showed defects in macronutrient metabolism, pH homeostasis, and cell division under photomixotrophic conditions, consistent with an essential role of AqpZ in glucose metabolism.
authors.affiliation: Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University Aobayama 6-6-07, Sendai 980-8579, Japan.
authors.forename: Masaro
authors.initials: M
authors.lastname: Akai
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Onai
authors.forename: Miyako
authors.initials: M
authors.lastname: Kusano
authors.forename: Mayuko
authors.initials: M
authors.lastname: Sato
authors.forename: Henning
authors.initials: H
authors.lastname: Redestig
authors.forename: Kiminori
authors.initials: K
authors.lastname: Toyooka
authors.forename: Megumi
authors.initials: M
authors.lastname: Morishita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyake
authors.forename: Akihiro
authors.initials: A
authors.lastname: Hazama
authors.forename: Vanessa
authors.initials: V
authors.lastname: Checchetto
authors.forename: Ildikò
authors.initials: I
authors.lastname: Szabò
authors.forename: Ken
authors.initials: K
authors.lastname: Matsuoka
authors.forename: Kazuki
authors.initials: K
authors.lastname: Saito
authors.forename: Masato
authors.initials: M
authors.lastname: Yasui
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ishiura
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Uozumi
mesh_terms: D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D017353:Gene Deletion; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000235:genetics / Q000378:metabolism; D009994:Osmolar Concentration; D010427:Pentose Phosphate Pathway / Q000502:physiology; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D001426:Bacterial Proteins; D051246:Glucose Transport Proteins, Facilitative; D005947:Glucose