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- Title
Adenosine stimulates anabolic metabolism in developing castor bean ( Ricinus communis L.) cotyledons.
- Authors
Flörchinger, Martin; Zimmermann, Marc; Traub, Michaela; Neuhaus, H. Ekkehard; Möhlmann, Torsten
- Abstract
In previous experiments it was shown that Castor-bean ( Ricinus communis) endosperm releases carbohydrates, amino acids and nucleoside derivatives, which are subsequently imported into the developing cotyledons (Kombrink and Beevers in Plant Physiol 73:370–376, ). To investigate the importance of the most prominent nucleoside adenosine for the metabolism of growing Ricinus seedlings, we supplied adenosine to cotyledons of 5-days-old seedlings after removal of the endosperm. This treatment led to a 16% increase in freshweight of intact seedlings within 16 h, compared to controls. Using detached cotyledons, we followed uptake of radiolabelled adenosine and identified 40% of label in solubles (mostly ATP and ADP), 46% incorporation in RNA and 2.5% in DNA, indicating a highly active salvage pathway. About 7% of freshly imported adenosine entered the phloem, which indicates a major function of adenosine for cotyledon metabolism. Import and conversion of adenosine improved the energy content of cotyledons as revealed by a substantially increased ATP/ADP ratio. This effect was accompanied by slight increases in respiratory activity, decreased levels of hexose phosphates and increased levels of fructose-1,6-bisphosphate and triose phosphates. These alterations indicate a stimulation of glycolytic flux by activation of phosphofructokinase, and accordingly we determined a higher activity of this enzyme. Furthermore the rate of [14C]-sucrose driven starch biosynthesis in developing castor-bean is significantly increased by feeding of adenosine. In conclusion, our data indicate that adenosine imported from mobilizing endosperm into developing castor-bean cotyledons fulfils an important function as it promotes anabolic reactions in this rapidly developing tissue.
- Subjects
CASTOR beans; PLANT metabolism; ADENOSINES; AMINO acids; NUCLEOSIDES; PLANT physiology; SEEDLINGS; PLANT growth; RICINUS
- Publication
Planta: An International Journal of Plant Biology, 2006, Vol 223, Issue 2, p340
- ISSN
0032-0935
- Publication type
Article
- DOI
10.1007/s00425-005-0091-1