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Carbon partitioning in leaves and tubers of transgenic potato plants with reduced activity of fructose‐6‐phosphate,2‐kinase/fructose‐2,6‐bisphosphatase
Author(s) -
Rung Jesper H.,
Draborg Henriette H.,
Jørgensen Kirsten,
Nielsen Tom H.
Publication year - 2004
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.0031-9317.2004.00318.x
Subject(s) - fructose , sucrose , hexose , biochemistry , sugar , starch , complementary dna , metabolism , carbohydrate , fructose 2,6 bisphosphate , solanaceae , sucrose phosphate synthase , solanum tuberosum , fructose 1,6 bisphosphatase , chemistry , biology , botany , sucrose synthase , enzyme , gene , glycolysis , invertase , phosphofructokinase
The role of fructose‐2,6‐bisphosphate (Fru‐2,6‐P 2 ) in regulation of carbon metabolism was investigated in transgenic potato plants ( Solanum tuberosum L. cv Dianella) transformed with a vector containing a cDNA‐sequence encoding fructose‐6‐phosphate,2‐kinase (F6P,2‐K, EC 2.7.1.105)/fructose‐2,6‐bisphosphatase (F26BPase, EC 3.1.3.46) in sense or antisense direction behind a CaMV 35S promoter. The activity of F6P,2‐K in leaves was reduced to 5% of wild‐type (WT) activity, and the level of Fru‐2,6‐P 2 was reduced both in leaves (10% of the WT level) and in tubers (40% of the WT level). Analysis of photosynthetic 14 CO 2 metabolism, showed that in plant lines with reduced Fru‐2,6‐P 2 level the carbon partitioning in the leaves was changed in favour of sucrose biosynthesis, and the soluble sugars‐to‐starch labelling ratio was doubled. The levels of soluble sugars and hexose phosphates also increased in leaves of the transgenic plants. Most notably, the levels of hexoses were four‐ to six‐fold increased in the transgenic plants. In tubers with reduced levels of Fru‐2,6‐P 2 only minor effects on carbohydrate levels were observed. Furthermore, carbon assimilation in tuber discs supplied with [U‐ 14 C]‐sucrose showed only a moderate increase in labelling of hexoses and a decreased labelling of starch. Similar results were obtained using [U‐ 14 C]‐glucose. No differences in growth of the transgenic lines and the WT were observed. Our data provide evidences that Fru‐2,6‐P 2 is an important factor in the regulation of photosynthetic carbon metabolism in potato leaves, whereas the direct influence of Fru‐2,6‐P 2 on tuber metabolism was limited.