Thylakoid potassium channel is required for efficient photosynthesis in cyanobacteria.
A potassium channel (SynK) of the cyanobacterium Synechocystis sp. PCC 6803, a photoheterotrophic model organism for the study of photosynthesis, has been recently identified and demonstrated to function as a potassium selective channel when expressed in a heterologous system and to be located predominantly to the thylakoid membrane in cyanobacteria. To study its physiological role, a SynK-less knockout mutant was generated and characterized. Fluorimetric experiments indicated that SynK-less cyanobacteria cannot build up a proton gradient as efficiently as WT organisms, suggesting that SynK might be involved in the regulation of the electric component of the proton motive force. Accordingly, measurements of flash-induced cytochrome b(6)f turnover and respiration pointed to a reduced generation of ΔpH and to an altered linear electron transport in mutant cells. The lack of the channel did not cause an altered membrane organization, but decreased growth and modified the photosystem II/photosystem I ratio at high light intensities because of enhanced photosensitivity. These data shed light on the function of a prokaryotic potassium channel and reports evidence, by means of a genetic approach, on the requirement of a thylakoid ion channel for optimal photosynthesis.
Department of Biology,  University of Padova, 35121 Padova,  Italy.
Vanessa
V
Checchetto
Anna
A
Segalla
Guillaume
G
Allorent
Nicoletta
N
La Rocca
Luigi
L
Leanza
Giorgio Mario
GM
Giacometti
Nobuyuki
N
Uozumi
Giovanni
G
Finazzi
Elisabetta
E
Bergantino
Ildikò
I
Szabò
D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D055786:Gene Knockout Techniques; D008564:Membrane Potentials / Q000502:physiology; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000502:physiology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000502:physiology; D045331:Photosystem I Protein Complex / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000502:physiology; D015221:Potassium Channels / Q000235:genetics / Q000502:physiology*; D011522:Protons; D046939:Synechocystis / Q000235:genetics / Q000502:physiology*; D020524:Thylakoids / Q000502:physiology*
D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D015221:Potassium Channels; D011522:Protons; D002734:Chlorophyll; D010100:Oxygen