title: Anaerobiosis induced state transition: a non photochemical reduction of PQ pool mediated by NDH in Arabidopsis thaliana.
abstract: BACKGROUND
  Non photochemical reduction of PQ pool and mobilization of LHCII between PSII and PSI are found to be linked under abiotic stress conditions. The interaction of non photochemical reduction of PQ pool and state transitions associated physiological changes are critically important under anaerobic condition in higher plants.
  
  
  RESULTS
  The present study focused on the effect of anaerobiosis on non-photochemical reduction of PQ pool which trigger state II transition in Arabidopsis thaliana. Upon exposure to dark-anaerobic condition the shape of the OJIP transient rise is completely altered where as in aerobic treated leaves the rise is unaltered. Rise in F(o) and F(J) was due to the loss of oxidized PQ pool as the PQ pool becomes more reduced. The increase in F(o)' was due to the non photochemical reduction of PQ pool which activated STN7 kinase and induced LHCII phosphorylation under anaerobic condition. Further, it was observed that the phosphorylated LHCII is migrated and associated with PSI supercomplex increasing its absorption cross-section. Furthermore, evidences from crr2-2 (NDH mutant) and pgr5 mutants (deficient in non NDH pathway of cyclic electron transport) have indicated that NDH is responsible for non photochemical reduction of the PQ pool. We propose that dark anaerobic condition accelerates production of reducing equivalents (such as NADPH by various metabolic pathways) which reduce PQ pool and is mediated by NDH leading to state II transition.
  
  
  CONCLUSIONS
  Anaerobic condition triggers non photochemical reduction of PQ pool mediated by NDH complex. The reduced PQ pool activates STN7 kinase leading to state II transition in A. thaliana.
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, India.
authors.forename: Sreedhar
authors.initials: S
authors.lastname: Nellaepalli
authors.forename: Sireesha
authors.initials: S
authors.lastname: Kodru
authors.forename: Malavath
authors.initials: M
authors.lastname: Tirupathi
authors.forename: Rajagopal
authors.initials: R
authors.lastname: Subramanyam
mesh_terms: D000693:Anaerobiosis / Q000235:genetics / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism / Q000502:physiology; D004579:Electron Transport / Q000502:physiology; D005453:Fluorescence; D008027:Light; D010084:Oxidation-Reduction; D045331:Photosystem I Protein Complex / Q000378:metabolism / Q000502:physiology; D045332:Photosystem II Protein Complex / Q000378:metabolism / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology; D010971:Plastoquinone / Q000737:chemistry / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002237:Carbohydrate Dehydrogenases; C020669:Glycerate dehydrogenase; D017346:Protein Serine-Threonine Kinases; C497212:STN7 protein, Arabidopsis; D010971:Plastoquinone