Journal Article

Induction of a Crassulacean Acid-like Metabolism in the C<sub>4</sub> Succulent Plant, <i>Portulaca oleracea</i> L.: Study of Enzymes Involved in Carbon Fixation and Carbohydrate Metabolism

María V. Lara, María F. Drincovich and Carlos S. Andreo

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 5, pages 618-626
Published in print May 2004 | ISSN: 0032-0781
Published online May 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch073
Induction of a Crassulacean Acid-like Metabolism in the C4 Succulent Plant, Portulaca oleracea L.: Study of Enzymes Involved in Carbon Fixation and Carbohydrate Metabolism

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The C4 succulent plant Portulaca oleracea shifts its photosynthetic metabolism to crassulacean acid metabolism (CAM) after 23 d of withholding water. This is accounted by diurnal acid fluctuation, net nocturnal but not day CO2 uptake and drastic changes in phosphoenolpyruvate carboxylase (PEPC) kinetic and regulatory properties [Lara et al. (2003) Photosynth. Res. 77: 241]. The goal of the present work was to characterize the CAM activity in leaves of P. oleracea during water stress through the study of enzymes involved in carbon fixation and carbohydrate metabolism. After drought stress, a general decrease in the photosynthetic metabolism, as accounted by the decrease in the net CO2 fixation and in the activity of enzymes such as ribulose-1,5-bisphosphate carboxylase/oxygenase, PEPC, pyruvate orthophosphate dikinase, phosphoenolpyruvate carboxykinase and NAD-malic enzyme was observed. We also found changes in the day/night activities and level of immunoreactive protein of some of these enzymes which were correlated to night CO2 fixation, as occurs under CAM metabolism. Based on the results obtained, including those from in situ immunolocalization studies, we propose a scheme for the possible CO2 fixation pathways used by P. oleracea under conditions of sufficient and limiting water supply.

Keywords: Keywords: C4 metabolism — Crassulacean acid metabolism — Drought stress — NAD-malic enzyme — Phosphoenolpyruvate carboxylase — Portulaca oleracea.; Abbreviations: BSC, bundle sheath cell; CAM, crassulacean acid metabolism; G3PDH, glycerol-3-phosphate dehydrogenase; GAPDHnP, nonphosphorylating glyceraldehyde-3-P dehydrogenase; G6PDH, glucose-6-phosphate dehydrogenase; MC, mesophyll cell; NAD-MDH, NAD-malate dehydrogenase; NADP-MDH, NADP-malate dehydrogenase; NAD-ME, NAD-malic enzyme; NADP-ME, NADP-malic enzyme; PEPC, phosphoenolpyruvate carboxylase; PEPCK, phosphoenolpyruvate carboxykinase; PFK, ATP-dependent phosphofructokinase; PFP, PPi-dependent phosphofructokinase; PPDK, pyruvate orthophosphate dikinase; RuBisCO, ribulose biphosphate carboxylase-oxygenase; TPI, triosephosphateisomerase; WSC, water storage cell.

Journal Article.  5363 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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