Down-regulation of pyrophosphate: fructose 6-phosphate 1-phosphotransferase (PFP) activity in sugarcane enhances sucrose accumulation in immature internodes |
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Authors: | Jan-Hendrik Groenewald Frederik Coenraad Botha |
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Institution: | (1) Institute for Plant Biotechnology, Stellenbosch University, Private Bag X1, Matieland, 7602, South Africa;(2) South African Sugarcane Research Institute, Private Bag X02, Mount Edgecombe, 4300, South Africa |
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Abstract: | Pyrophosphate: fructose 6-phosphate 1-phosphotransferase (PFP) activity was successfully down-regulated in sugarcane using
constitutively expressed antisense and untranslatable forms of the sugarcane PFP-β gene. In young internodal tissue activity
was reduced by up to 70% while no residual activity could be detected in mature tissues. The transgenic plants showed no visible
phenotype or significant differences in growth and development under greenhouse and field conditions. Sucrose concentrations
were significantly increased in the immature internodes of the transgenic plants but not in the mature internodes. This contributed
to an increase in the purity of the immature tissues, resembling an early ripening phenotype. Both the immature and mature
internodes of the transgenic plants had significantly higher fibre contents. These findings suggest that PFP influences the
ability of young, biosynthetically active sugarcane culm tissue to accumulate sucrose but that the equilibrium of the glycolytic
intermediates, including the stored sucrose, is restored when ATP-dependent phosphofructokinase and the residual PFP activity
is sufficient to sustain the required glycolytic flux as the tissue matures. Moreover, it suggests a role for PFP in glycolytic
carbon flow, which could be rate limiting under conditions of high metabolic activity. |
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Keywords: | Pyrophosphate: fructose-6-phosphate 1-phosphotransferase PFP Carbon partitioning Sucrose metabolism Transgenic sugarcane Gene silencing |
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