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The location of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in the leaf mesophyll of some dicotyledonous C4 plants
was confirmed by immunofluorescent labelling. The anti-RuBPCO immune serum was obtained by inoculating a rabbit with commercially
obtained RuBPCO. Specificity of these antibodies was tested by immunodiffusion, immunoelectrophoresis, and Western blotting.
Fresh hand-cuts of leaves from dicotyledonous C4 plants, Amaranthus caudatus, A. dubius, Gomphrena globosa, and Portulaca oleracea, were incubated with the conjugated anti-RuBPCO immune serum and then with a commercial FITC-anti-rabbit IgG conjugate. Nerium oleander was used a control C3 plant pattern and Zea mays as a C4 plant pattern. The immunofluorescent label was distributed in both mesophyll and bundle sheath in all the C4 plants
tested. It is an unequivocal proof that in the C4 dicotyledonous plants the RuBPCO is not only located in the chloroplasts
of the bundle sheath cells but also in the chloroplasts of the mesophyll cells. In these plants therefore, the C4 pathway
cannot exclusively be viewed as an intercellular level concentration mechanism. In the mesophyll cytoplasm, phosphoenolpyruvate
carboxylase traps CO2, while in the mesophyll chloroplasts, RuBPCO operates with atmospheric CO2 and CO2 from the C4 decarboxylation
step at an intracellular level, which could mean a significant energetic economy. The CO2 from photorespiration could be saved
and reincorporated. Location of RuBPCO in the mesophyll and/or bundle sheath chloroplasts is a matter of inter- and intracellular
compartmentation which makes another variation of C4 photosynthetic pathway possible.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
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