Reduced glutamine synthetase activity plays a role in control of photosynthetic responses to high light in barley leaves.
The chloroplastic glutamine synthetase (GS, EC 6.3.1.2) activity was previously shown to be the limiting step of photorespiratory pathway. In our experiment, we examined the photosynthetic high-light responses of the GS2-mutant of barley (Hordeum vulgare L.) with reduced GS activity, in comparison to wild type (WT). The biophysical methods based on slow and fast chlorophyll fluorescence induction, P700 absorbance, and gas exchange measurements were employed. Despite the GS2 plants had high basal fluorescence (F0) and low maximum quantum yield (Fv/Fm), the CO2 assimilation rate, the PSII and PSI actual quantum yields were normal. On the other hand, in high light conditions the GS2 had much higher non-photochemical quenching (NPQ), caused both by enhanced capacity of energy-dependent quenching and disconnection of PSII antennae from reaction centers (RC). GS2 leaves also maintained the PSII redox poise (QA(-)/QA total) at very low level; probably this was reason why the observed photoinhibitory damage was not significantly above WT. The analysis of fast chlorophyll fluorescence induction uncovered in GS2 leaves substantially lower RC to antenna ratio (RC/ABS), low PSII/PSI ratio (confirmed by P700 records) as well as low PSII excitonic connectivity.
Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76 Nitra, Slovak Republic. Electronic address: marian.brestic@uniag.sk.
Marian
M
Brestic
Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76 Nitra, Slovak Republic. Electronic address: marek.zivcak@uniag.sk.
Marek
M
Zivcak
Department of Plant Physiology, Slovak Agricultural University, Tr. A. Hlinku 2, 949 76 Nitra, Slovak Republic.
Katarina
K
Olsovska
Key Laboratory of Coastal Environmental Processes & Ecological Remediation and Key Laboratory of Coastal Biology & Bioresources Utilization, Yantai Institute of Coastal Zone Research (YIC), Chinese Academy of Sciences (CAS), PR China; Institute of Life Sciences, Qingdao University of Science & Technology, Qingdao 266042, PR China.
Hong-Bo
HB
Shao
Department of Plant Physiology, Faculty of Agriculture and Biology, Warsaw Agricultural University SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland.
Hazem M
HM
Kalaji
Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow 127276, Russia; Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region 142290, Russia.
Suleyman I
SI
Allakhverdiev
D002245:Carbon Dioxide / Q000378:metabolism; D019069:Cell Respiration; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D005974:Glutamate-Ammonia Ligase / Q000235:genetics / Q000378:metabolism*; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000502:physiology / Q000528:radiation effects; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism
D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D002245:Carbon Dioxide; D005974:Glutamate-Ammonia Ligase
Barley; Chlorophyll fluorescence; Glutamine synthetase; Non-photochemical quenching; Photoinhibition; Photorespiration