Metabolism of the Raffinose Family Oligosaccharides in Leaves of Ajuga reptans L. (Inter- and Intracellular Compartmentation).
AUTOR(ES)
Bachmann, M.
RESUMO
We recently suggested that leaves of the frost-hardy species Ajuga reptans L. (Lamiaceace) contain two pools of raffinose family oligosaccharides (RFO): a large long-term storage pool in the mesophyll, possibly also involved in frost resistance, and a transport pool in the phloem (M. Bachmann, P. Matile, F. Keller [1994] Plant Physiol 105: 1335-1345). In the present study, the inter- and intracellular compartmentation of anabolic RFO metabolism was investigated by comparing whole-leaf tissue with mesophyll protoplasts and vacuoles. The studies showed the mesophyll to be the primary site of RFO synthesis in A. reptans. Mesophyll protoplasts were capable of RFO formation upon in vitro 14CO2 photosynthesis. Sucrose-phosphate synthase, galactinol synthase, and the galactinol-independent galactosyltransferase, which is responsible for RFO chain elongation, were located predominantly in the mesophyll protoplasts. The percentage of stachyose synthase in the mesophyll changed greatly during the cold-acclimation period (from 26% at the beginning to 88% after 20 d). The remainder was most probably in the intermediary cells of the phloem. Compartmentation studies in which mesophyll protoplasts were compared with vacuoles isolated from them showed that, of the components of the RFO storage pool, galactinol synthase, stachyose synthase, myo-inositol, galactinol, and sucrose were extravacuolar (most probably cytosolic), whereas galactinol-independent galactosyltransferase and higher RFO oligomers (with degree of polymerization 4) were vacuolar. Raffinose was found in both locations and might serve as a cryoprotectant.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=161401Documentos Relacionados
- Metabolism of the Raffinose Family Oligosaccharides in Leaves of Ajuga reptans L. (Cold Acclimation, Translocation, and Sink to Source Transition: Discovery of Chain Elongation Enzyme).
- Influence of light regimes on respiration, activity of alternative respiratory pathway and carbohydrates content in mature leaves of Ajuga reptans L.
- Demonstration of the Intercellular Compartmentation of l-Menthone Metabolism in Peppermint (Mentha piperita) Leaves 1
- Metabolism of Monoterpenes 12: EVIDENCE FOR COMPARTMENTATION OF l-MENTHONE METABOLISM IN PEPPERMINT (MENTHA PIPERITA) LEAVES
- Water Deficit Effects on Raffinose Family Oligosaccharide Metabolism in Coleus1