Intercellular compartmentation of sucrose synthesis in leaves of Zea mays L. |
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Authors: | Robert T. Furbank Mark Stitt Christine H. Foyer |
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Affiliation: | (1) Research Institute for Photosynthesis, Department of Botany, University of Sheffield, S10 2TN Sheffield, UK;(2) Present address: Lehrstuhl für Biochemie der Pflanze, Untere Karspüle 2, D-3400 Göttingen, FRG |
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Abstract: | The incorporation of 14C into sucrose and hexose phosphates during steady-state photosynthesis was examined in intact leaves of Zea mays L. plants. The compartmentation of sucrose synthesis between the bundle sheath and mesophyll cells was determined by the rapid fractionation of the mesophyll and comparison of the labelled sucrose in this compartment with that in a complete leaf after homogenisation. From these experiments it was concluded that the majority of sucrose synthesis occurred in the mesophyll cell type (almost 100% when the time-course of sucrose synthesis was extrapolated to the time of 14C-pulsing). The distribution of enzymes involved in sucrose synthesis between the two cell types indicated that sucrose-phosphate synthetase was predominantly located in the mesophyll, as was cytosolic (neutral) fructose-1,6-bisphosphatase activity. Stromal (alkaline) fructose-1,6-bisphosphatase activity was found almost exclusively in the bundle-sheath cells. No starch was found in the mesophyll tissue. These data indicate that in Zea mays starch and sucrose synthesis are spatially, separated with sucrose synthesis occurring in the mesophyll compartment and starch synthesis in the bundle sheath. |
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Keywords: | Fructose 1,6-bisphosphatase Sucrose phosphate synthetase Sucrose synthesis Zea (sucrose synthesis) |
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