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

LARA, MARÍA VALERIA; MARIA FABIANA DRINCOVICH; ANDREO, CS

Plant and Cell Physiology

Japanese Society of Plant Physiology, Oxford University Press

Año: 2004 vol. 45 p. 618 - 626

0032-0781

P. oleracea is a succulent plant classified as C4. However, after 23 days of withholding water its photosynthetic metabolism shifts to CAM accounted by diurnal acid fluctuation, net nocturnal CO2 uptake without day CO2 acquisition and drastic changes in Phosphoenolpyruvate carboxylase (PEPC) kinetic and regulatory properties (Lara et. al., 2003). In this way, the goal of this project was to characterize the CAM activity in leaves of P. oleracea during water stress through the study of the enzymes involved in carbon fixation and carbohydrate metabolism. After 23 days of drought stress, we found a general decreased in the photosynthetic metabolism, as accounted by the decreased in the net CO2 fixation and the decreased in the activity of enzymes related to that metabolism such as Ribulose-1,5-bisphosphate carboxylase/oxygenase, PEPC, pyruvateorthophosphate dikinase, phosphoenolpyruvate carboxykinase and NAD-malic enzyme. We also reported changes in the day/night activities of some of these enzymes in relation to a night fixation of the CO2, which occurs under a CAM mode. In this way, the results obtained, including those from in situ immunolocalization studies, let us propose the metabolic pathways used by P. oleracea to fix CO2 under conditions of sufficient water supply and under drought stress conditions