In vivo occurrence of carbonyl residues in Phaseolus vulgaris proteins as a direct consequence of a chronic ozone stress

We aimed to show that a chronic and realistic ozone stress could induce in vivo formation of carbonyl groups in leaf proteins of bean (Phaseolus vulga ris L. cv Bergamo). Plants were grown in three open-top chambers with incre asing ozone concentrations: non-filtered air (NF), NF+40 nL.L-1, NF+80 nL.L -1 ozone 7 h.d(-1) for 22 d. Carbonyl contents in proteins, evaluation of R ubisco (EC 4.1.1.39) amounts and visible damages were systematically invest igated in primary and first trifoliate leaves. Visible ozone injuries clear ly reflected the total external ozone dose (expressed as AOT40) that the le af had suffered. Ozone was effective at inducing aldehydes and ketones form ation in bean proteins. This production of carbonyl groups increased with o zone concentration, the most relevant difference being observed on the Rubi sco small subunit (Rubisco SSU). Contrary to young first trifoliate leaves, older primary leaves from O-3-enriched atmospheres exhibited a two-fold de crease in Rubisco level. Carbonyl group formation in Rubisco SSU and decrea se in Rubisco level were not necessarily linked. Depending on ozone concent ration, exposure time and leaf age, these two effects were observed either together or separately for an almost similar external dose of ozone. To con clude, leaf symptoms, loss of Rubisco and oxidized Rubisco SSU could partic ipate in the assessment of the impact of a chronic ozone stress. (C) 2000 E ditions scientifiques et medicales Elsevier SAS.