Poster: Photosynthesis

Abs # 615: Induccion of a Crassulacean Acid like Metabolism in the C₄ plant Portulaca oleracea L. under drought conditions. Study of photosynthetic enzymes

Presenter:	Lara, María V, mlara@fbioyf.unr.edu.ar
Additional Authors	Drincovich, María F (A)   Podestá, Florencio E (A)   Andreo, Carlos S (A)
Affiliations:	(A): CEFOBI, CONICET, National University of Rosario

The species Portuca oleracea L. is a succulent dicot classified as C₄ according to the CO₂ fixation metabolism. However, after 21-23 days of drought stress the induction of a Crassulacean Acid like Metabolism (CAM-like) was evidenced by changes in the day/night CO₂ exchange pattern accompanied of periodic fluctuation in titratable acidity and malate level. Phosphoenolpyruvate carboxylase (PEPC) activity and regulation are also modified upon induction of a CAM-like metabolism in P. oleracea. In order to study in detail the transition of metabolism, specially the decarboxylating enzymes, we studied the following enzymes under both metabolic conditions: NADP-malic enzyme (NADP-ME), NAD-malic enzyme (NAD-ME), Phosphoenolpyruvate carboxykinase (PEPCK) and pyruvatephosphate dikinase (PPDK). We performed studies such as activity measurements, denatured Western blot analysis and in situ immunolocalization in P. oleracea leaves and compared with PEPC and Rubisco. The results obtained indicated that the activity and content (shown by Western blot studies and immunolocalization) of the decarboxylating enzymes and PEPC varied in an important manner in both tissue conditions (C₄ and CAM). However, the localization pattern of the enzymes remained invariant. In addition, some of them displayed changes in their activity during the day and night periods, confirming in this way, the change in the CO₂ metabolism fixation. Changes in leaf anatomy during the transition of metabolism were evidenced as well.