ISHS Acta Horticulturae 487: VI International Symposium on Processing Tomato & Workshop on Irrigation & Fertigation of Processing Tomato
EFFECTS OF OVEREXPRESSION OF SUCROSE PHOSPHATE SYNTHASE ON THE CARBOHYDRATE COMPOSITION OF TOMATO LEAVES AND FRUIT |
| Authors: | C.H. Foyer, E. Murchie, N. Galtier, B. Nguyen-Quoc, S. Yelle |
| Abstract:
Expression of maize sucrose phosphate synthase (SPS) cDNA under the control of the promoter of the small subunit of ribulose-1,5-bisphosphate carboxylase oxygenase led to an increase in maximal extractable SPS activity in leaves (up to 6.0-fold) and fruit (up to 2.5- fold) of Lycopersicon esculentum var. UC82B. SPS overexpression in leaves led to an increase in photosynthesis, particularly at high light and elevated CO2 (800–1500 μ1 l-1). Foliar sucrose synthesis was increased and starch accumulation was decreased in the leaves of the transformants. The ratio of sucrose to starch in the leaves of the transformants was higher than that of the untransformed controls even when plants were grown with CO2 enrichment. Plants overexpressing SPS showed no increase in total biomass accumulation or fruit yield. Sucrose synthase activity was increased by 27% in fruits from the transformed plants compared to untransformed controls. Seventy percent more sucrose was unloaded into 20-day old fruit from transformed plants and the turnover of unloaded sucrose was increased compared to untransformed controls. These results suggest that SPS overexpression modifies carbohydrate metabolism in both source and sink tissues, increasing the capacity of the source leaves to export sucrose and the sink strength of the tomato fruit. | |
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