caa a22 4500 47710021X CHVBK 20180405111538.0 cr unu---uuuuu 170330e19961201xx s 000 0 eng 10.1007/BF00231394 doi (NATIONALLICENCE)springer-10.1007/BF00231394 Control of photosynthesis in barley mutants with reduced activities of glutamine synthetase and glutamate synthase [Elektronische Daten] III. Aspects of glyoxylate metabolism and effects of glyoxylate on the activation state of ribulose-1,5-bisphosphate carboxylase-oxygenase [Rainer Häusler, Karen Bailey, Peter Lea, Richard Leegood] Heterozygous mutants of barley (Hordeum vulgare L. cv. Maris Mink) with decreased activities of chloroplastic glutamine synthetase (GS) between 97 and 47% of the wild type and ferredoxin dependent glutamate synthase (Fd-GOGAT) down to 64% of the wild type have been used to study aspects of glyoxylate metabolism and the effect of glyoxylate on the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in vivo. In the leaf, the extractable activities of serine:glyoxylate aminotransferase decreased with a decrease in GS whereas activities of glutamate and alanine:glyoxylate aminotransferase increased, pointing to a re direction of amino donors from serine to glutamate and alanine. Under ambient conditions, the leaf contents of glutamate and alanine declined continuously with a decrease in GS, in parallel with the decrease in total amino acids. Glycine, serine and asparagine contents decreased with a decrease in GS to approximately 70% of the wild type, but increased again with a further decrease in GS. At high irradiances and at low CO2 concentrations, glyoxylate contents exhibited a pronounced minimum between 60% and 80% GS. With a further decrease in GS, glyoxylate contents recovered and approached values similar to the wild type. The activation state of Rubisco showed a negative correlation with glyoxylate contents, indicating that a decrease in GS feeds back on the first step of carbon assimilation and photorespiration. The activation state of stromal fructose-1,6-bisphosphatase was unaffected by a decrease in GS or Fd-GOGAT, whereas the activation state of NADP dependent malate dehydrogenase changed in a complex manner. The CO2photocompensation point, Γ*, was appreciably increased in mutants with 47% GS. ‘Mitochondrial respiration' in the light (Rd) was reduced with a decrease in GS. Relative rates of CO2 release into CO2-free air between the wild type and the 47%-GS mutant correlated with determinations of Γ*. These data are consistent with the view that when GS is decreased there is an increased oxidative decarboxylation of glyoxylate resulting from a decreased availability of amino donors for the transamination of glyoxylate to glycine, and that when GS activities are lower than 70% of the wild type an additional mechanism operates to reduce the photorespiratory loss of ammonia. Springer-Verlag, 1996 Hordeum nationallicence Glutamine synthetase nationallicence Glyoxylate nationallicence Glyoxylate metabolism nationallicence Photorespiration nationallicence Ribulose-1,5-bisphosphate carboxylase-oxygenase nationallicence AGAT : nine:glyoxylate aminotransferase nationallicence FBPase : fructose-1,6-bisphosphatase nationallicence Fd-GOGAT : ferredoxin dependent glutamate synthase nationallicence GGAT : glutamate:glyoxylate aminotransferase nationallicence GS : glutamine synthetase nationallicence MDH : malate dehydrogenase nationallicence PFD : photon flux density nationallicence Rubisco : ribulose-1,5-bisphosphate carboxylase-oxygenase nationallicence SGAT : serine:glyoxylate aminotransferase nationallicence Häusler Rainer Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut Bailey Karen Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut Lea Peter Department of Biological Sciences, University of Lancaster, Bailrigg, LA1 4YQ, Lancaster, UK aut Leegood Richard Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut Planta Springer-Verlag 200/4(1996-12-01), 388-396 0032-0935 200:4<388 1996 200 425 https://doi.org/10.1007/BF00231394 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00231394 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Häusler Rainer Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut NATIONALLICENCE 700 1- Bailey Karen Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut NATIONALLICENCE 700 1- Lea Peter Department of Biological Sciences, University of Lancaster, Bailrigg, LA1 4YQ, Lancaster, UK aut NATIONALLICENCE 700 1- Leegood Richard Robert Hill Institute and Department of Animal and Plant Sciences, University of Sheffield, S10 2TN, Sheffield, UK aut NATIONALLICENCE 773 0- Planta Springer-Verlag 200/4(1996-12-01), 388-396 0032-0935 200:4<388 1996 200 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer