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ABSTRACTWe investigated the role of metabolite transporters in cold acclimation by comparing the responses of wild‐type (WT) Arabidopsis thaliana (Heynh.) with that of transgenic plants over‐expressing sucrose‐phosphate synthase (SPSox) or with that of antisense repression of cytosolic fructose‐1,6‐bisphosphatase (FBPas). Plants were grown at 23 °C and then shifted to 5 °C. We compared the leaves shifted to 5 °C for 3 and 10 d with new leaves that developed at 5 °C with control leaves on plants at 23 °C. At 23 °C, ectopic expression of SPS resulted in 30% more carbon being fixed per day and an increase in sucrose export from source leaves. This increase in fixation and export was supported by increased expression of the plastidic triose‐phosphate transporter AtTPT and, to a lesser extent, the high‐affinity Suc transporter AtSUC1. The improved photosynthetic performance of the SPSox plants was maintained after they were shifted to 5 °C and this was associated with further increases in AtSUC1 expression but with a strong repression of AtTPT mRNA abundance. Similar responses were shown by WT plants during acclimation to low temperature and this response was attenuated in the low sucrose producing FBPas plants. These data suggest that a key element in recovering flux through carbohydrate metabolism in the cold is to control the partitioning of metabolites between the chloroplast and the cytosol, and Arabidopsis modulates the expression of AtTPT to maintain balanced carbon flow. Arabidopsis also up‐regulates the expression of AtSUC1, and to lesser extent AtSUC2, as down‐stream components facilitate sucrose transport in leaves that develop at low temperatures.
Sucrose, Starch Degradation, Biosynthesis Pathway, Triose Phosphate/Phosphate Translocator, Phosphate Synthase Activity, Arabidopsis, Plants Nicotiana-Tabacum, Cold-Acclimation, Bacterial Proteins, Gene Expression Regulation, Plant, Freezing Tolerance, Fructose 2,6-Bisphosphate, Arabidopsis Proteins, Circadian Rhythm Signaling Peptides and Proteins, Antisense Repression, Plant Sciences, Starch, Winter Rye, Plants, Genetically Modified, Carbon, Cold Temperature, Carrier Proteins
Sucrose, Starch Degradation, Biosynthesis Pathway, Triose Phosphate/Phosphate Translocator, Phosphate Synthase Activity, Arabidopsis, Plants Nicotiana-Tabacum, Cold-Acclimation, Bacterial Proteins, Gene Expression Regulation, Plant, Freezing Tolerance, Fructose 2,6-Bisphosphate, Arabidopsis Proteins, Circadian Rhythm Signaling Peptides and Proteins, Antisense Repression, Plant Sciences, Starch, Winter Rye, Plants, Genetically Modified, Carbon, Cold Temperature, Carrier Proteins
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