Evidence for intracellular spatial separation of hexokinases and fructokinases in tomato plants
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Four hexokinase (LeHXK1–4) and four fructokinase (LeFRK1–4) genes were identified in tomato plants. Previous GFP fusion studies indicate that the gene product of LeHXK3 is associated with the mitochondria while that of LeHXK4 is located within plastids. In this study we found that the enzyme encoded by the fructokinase gene LeFRK3 is also located within plastids. The presence of LeFrk3 enzyme in plastids raises the question of the origin of fructose in these organelles. The other three FRKs enzymes, LeFrk1&2&4, are located in the cytosol. Unlike LeFrk1&2&4, the two additional HXKs, LeHxk1&2, share a common membrane anchor domain and are associated with the mitochondria similar to LeHxk3. The difference in the locations of the cytoplasmic FRK and HXK isozymes suggests that glucose phosphorylation is confined to defined special intracellular localizations while fructose phosphorylation is less confined.
KeywordsFructokinase GFP Hexokinase Hexose phosphorylation Intracellular localization Tomato (Lycopersicon esculentum)
Green fluorescent protein
This research was supported by research grant No. 582/01 from The Israel Science Foundation, and by research grant No. IS-3326-02C from BARD, the United States—Israel Binational Agricultural and Development Fund.
- Cho JI, Ryoo N, Ko S, Lee SK, Lee J, Jung KH, Lee YH, Bhoo SH, Winderickx J, An G, Hahn TR, Jeon JS (2006) Structure, expression, and functional analysis of the hexokinase gene family in rice (Oryza sativa L.). Planta (in press)Google Scholar
- Draper J, Scott R, Hamil J (1988) Transformation of dicotiledonous plant cells using the Ti plasmid of A. tumefaciens and the Ri plasmid of A. rhizogenes. Blackwell, OxfordGoogle Scholar
- Kandel-Kfir M, Damari-Weissler H, German MA, Gidoni D, Mett A, Belausov E, Petreikov M, Adir N, Granot D (2006) Two newly identified membrane-associated and plastidic tomato HXKs: characteristics, predicted structure and intracellular localization. PlantaGoogle Scholar
- Renz A, Stitt M (1993) Substrate specificity and product inhibition of different forms of fructokinases and hexokinases in developing potato tubers. Planta 190:166–175Google Scholar
- Taylor MA, Ross HA, Gardner A, Davies HV (1995) Characterization of a cDNA encoding fructokinase from potato (Solanum tuberosum L). J Plant Physiol 145:253–256Google Scholar