title: Formation of chloroplast protrusions and catalase activity in alpine Ranunculus glacialis under elevated temperature and different CO2/O2 ratios.
abstract: Chloroplast protrusions (CPs) have frequently been observed in plants, but their significance to plant metabolism remains largely unknown. We investigated in the alpine plant Ranunculus glacialis L. treated under various CO2 concentrations if CP formation is related to photorespiration, specifically focusing on hydrogen peroxide (H2O2) metabolism. Immediately after exposure to different CO2 concentrations, the formation of CPs in leaf mesophyll cells was assessed and correlated to catalase (CAT) and ascorbate peroxidase (APX) activities. Under natural irradiation, the relative proportion of chloroplasts with protrusions (rCP) was highest (58.7 %) after exposure to low CO2 (38 ppm) and was lowest (3.0 %) at high CO2 (10,000 ppm). The same relationship was found for CAT activity, which decreased from 34.7 nkat mg(-1) DW under low CO2 to 18.4 nkat mg(-1) DW under high CO2, while APX activity did not change significantly. When exposed to natural CO2 concentration (380 ppm) in darkness, CP formation was significantly lower (18.2 %) compared to natural solar irradiation (41.3 %). In summary, CP formation and CAT activity are significantly increased under conditions that favour photorespiration, while in darkness or at high CO2 concentration under light, CP formation is significantly lower, providing evidence for an association between CPs and photorespiration.
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria. Othmar.Buchner@uibk.ac.at.
authors.forename: Othmar
authors.initials: O
authors.lastname: Buchner
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria.
authors.forename: Tim
authors.initials: T
authors.lastname: Moser
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria.
authors.forename: Matthias
authors.initials: M
authors.lastname: Karadar
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Roach
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria.
authors.forename: Ilse
authors.initials: I
authors.lastname: Kranner
authors.affiliation: Institute of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestrasse 15, 6020, Innsbruck, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Holzinger
mesh_terms: D000064:Acclimatization; D000531:Altitude; D060387:Ascorbate Peroxidases / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism / Q000494:pharmacology*; D002374:Catalase / Q000378:metabolism*; D002736:Chloroplasts / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects / Q000648:ultrastructure; D003624:Darkness; D004305:Dose-Response Relationship, Drug; D006184:Habits; D006358:Hot Temperature; D007425:Intracellular Membranes / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects / Q000648:ultrastructure; D008027:Light; D008857:Microscopy, Interference; D010100:Oxygen / Q000378:metabolism / Q000494:pharmacology*; D017440:Photoperiod; D010788:Photosynthesis / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism*; D031947:Ranunculus / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects / Q000648:ultrastructure; D013997:Time Factors
chemical_list: D010940:Plant Proteins; D002245:Carbon Dioxide; D060387:Ascorbate Peroxidases; D002374:Catalase; D010100:Oxygen
keywords: Ascorbate peroxidase; Hydrogen peroxide; Photorespiration; Stromules; Ultrastructure