title: Loss of the SPHF homologue Slr1768 leads to a catastrophic failure in the maintenance of thylakoid membranes in Synechocystis sp. PCC 6803.
abstract: BACKGROUND
  In cyanobacteria the photosystems are localised to, and maintained in, specialist membranes called the thylakoids. The mechanism driving the biogenesis of the thylakoid membranes is still an open question, with only two potential biogenesis factors, Vipp1 and Alb3 currently identified.
  
  
  RESULTS
  We generated a slr1768 knockout using the pGEM T-easy vector and REDIRECT. By comparing growth and pigment content (chlorophyll a fluoresence) of the Δslr1768 mutant with the wild-type, we found that Δslr1768 has a conditional phenotype; specifically under high light conditions (130 µmol m(-2) s(-1)) thylakoid biogenesis is disrupted leading to cell death on a scale of days. The thylakoids show considerable disruption, with loss of both structure and density, while chlorophyll a density decreases with the loss of thylakoids, although photosynthetic efficiency is unaffected. Under low light (30 µmol m(-2) s(-1)) the phenotype is significantly reduced, with a growth rate similar to the wild-type and only a low frequency of cells with evident thylakoid disruption.
  
  
  CONCLUSIONS
  This is the first example of a gene that affects the maintenance of the thylakoid membranes specifically under high light, and which displays a phenotype dependent on light intensity. Our results demonstrate that Slr1768 has a leading role in acclimatisation, linking light damage with maintenance of the thylakoids.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, London, United Kingdom.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Bryan
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Burroughs
authors.forename: Carol
authors.initials: C
authors.lastname: Evered
authors.forename: Joanna
authors.initials: J
authors.lastname: Sacharz
authors.forename: Anja
authors.initials: A
authors.lastname: Nenninger
authors.forename: Conrad W
authors.initials: CW
authors.lastname: Mullineaux
authors.forename: Edward M
authors.initials: EM
authors.lastname: Spence
mesh_terms: D000064:Acclimatization; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002462:Cell Membrane / Q000502:physiology*; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D008027:Light; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000502:physiology*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D002734:Chlorophyll; D000077194:Chlorophyll A