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Peters, W; Beck, E; Piepenbrock, M; Lenz, B; Schmitt, JM: Cytokinin as a negative effector of phosphoenolpyruvate carboxylase induction in Mesembryanthemum crystallinum, Journal of Plant Physiology, 151, 362-367 (1997), doi:10.1016/S0176-1617(97)80266-0
Abstract:
The possible role of cytokinin in the signal transduction pathway leading to phospho enol pyruvate carboxylase (PEPCase; EC 4.1.1.31) induction in the halophilic species Mesembryanthemum crystallinum L. was investigated. PEPCase is known to be induced by water stress in this species. When 6-benzylaminopurine (BA) was applied to M. crystallinum plants, water deficit developed as indicated by a decrease in leaf water content and by accumulation of proline. This effect was least pronounced when BA was applied to the shoots. Application of BA to the roots resulted in stronger symptoms of water stress, and simultaneous application to the roots and the shoots was most effective, leading to a 40% decrease in leaf water content and a 20-fold increase in proline within 3 days. PEPCase mRNA and enzyme activity were increased in the root-treated plants but an additional application of BA to the leaves could prevent PEPCase induction efficiendy. We therefore investigated the possible role of endogenous cytokinins in CAM induction. Fourteen species of endogenous cytokinins could be identified and were measured quantitatively. Endogenous cytokinin content was negatively correlated with mRNA levels specific for PEPCase but showed only weak correlation with PEPCase activity. In excised, wilting leaves, cytokinins decreased and PEPCase mRNA strongly increased. In rehydrating excised leaves derived from pre-stressed plants, PEPCase mRNA was down-regulated, but cytokinins were essentially unchanged. Taken together, the data support a negative regulatory function of leaf cytokinins in PEPCase induction.

Letzte Änderung 02.07.2020