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Changes in levels of phosphoenolpyruvate carboxylase with induction of Crassulacean acid metabolism (CAM)‐like behavior in the C 4 plant Portulaca oleracea
Author(s) -
Mazen A. M. A.
Publication year - 1996
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1996.tb00681.x
Subject(s) - phosphoenolpyruvate carboxylase , portulaca , crassulacean acid metabolism , photoperiodism , biology , citrate synthase , botany , phosphoenolpyruvate carboxykinase , mesembryanthemum crystallinum , horticulture , photosynthesis , biochemistry , enzyme
Changes in levels of phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31, orthophosphate: oxaloacetate carboxy‐lyase, phosphorylating) were followed in leaves and stems of CAM‐expressing and non‐expressing Portulaca oleracea L. plants. CAM expression was induced by growing plants under an 8‐h photoperiod and water stress conditions (SD‐WS). Leaves and stems of these plants (designated CAM) expressed nocturnal acidification with an oscillation pattern and an amplitude characteristic of CAM plants. Generally, PEPC activity increased by ca 3‐fold during the period of CAM induction. Over the day/night cycle. PEPC activity oscillated in a pattern typical of CAM plants. Treatment of the other plant group (designated as non‐CAM) by growth under a 16‐h photoperiod and well‐watered conditions (LD‐WW) did not induce expression of the tested criteria of CAM in plants. In these plants, nocturnal acidification as well as changes in the magnitude of PEPC, activity and fluctuation pattern were undetectable. SDS‐PAGE of leaf extracts of the CAM‐expressing plants and the corresponding densitometric scans show progressive increase in the amount of PEPC subunit protein (ca 95 kDa) during the period of CAM induction. These results show that induction of CAM‐like characteristics in the C 4 plant Portulaca oleracea is also accompanied by increased PEPC activity, which may be partly due to an increase in enzyme synthesis.