Divergent Fructokinase Genes Are Differentially Expressed in Tomato

Kanayama, Yoshinori; Dai, Nir; Granot, David; Petreikov, Marina; Schaffer, Arthur A.; Bennett, A. B.

doi:10.1104/pp.113.4.1379

Cited by 76 publications

(61 citation statements)

References 31 publications

(39 reference statements)

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“…Four diVerent FRK-encoding genes, denoted LeFRK1-4, have been isolated from tomato (Solanum lycopersicon) plants (Kanayama et al 1997(Kanayama et al , 1998German et al 2002German et al , 2004Granot 2007). LeFRK2 is the major FRK gene expressed in most tissues, including stems, roots, and leaves (Kanayama et al 1997(Kanayama et al , 1998German et al 2002German et al , 2004.…”

Section: Introductionmentioning

confidence: 99%

LeFRK2 is required for phloem and xylem differentiation and the transport of both sugar and water

Damari-Weissler

Rachamilevitch

Aloni

et al. 2009

Planta

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It has been suggested that LeFRK2, the major fructose-phosphorylating enzyme in tomato plants, may be required for stem xylem development. Yet, we do not know if this enzyme affects the development of individual vessels, whether it affects water conductance, or whether it affects phloem development and sugar transport. Here, we show that suppression of LeFRK2 results in a significant reduction in the size of vascular cells and slows fiber maturation. The vessels in stems of LeFRK2-antisense plants are narrower than in WT plants and have thinner secondary cell walls. Although the cambium produces rounded secondary vessels, these vessels become deformed during the early stages of xylem maturation. Water conductance is then reduced in stems, roots, and leaves, suggesting that LeFRK2 influences xylem development throughout the entire vascular system. Interestingly, the build-up of positive xylem pressure under static (no-flow) conditions was also decreased. Suppression of LeFRK2 reduced the length and width of the sieve elements, as well as callose deposition. To examine the effect of LeFRK2 suppression on phloem transport, we created triple-grafted plants in which a portion of the wild-type stem was replaced with an antisense interstcok, and compared the contents of the transported sugar, sucrose, in the different portions of these stems. Sucrose contents above and within the LeFRK2-antisense interstock were significantly higher than those below the graft. These results show that the antisense interstock restricted the downward movement of sucrose, suggesting that LeFRK2 is required for both phloem and xylem development.

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Section: Introductionmentioning

confidence: 99%

LeFRK2 is required for phloem and xylem differentiation and the transport of both sugar and water

Damari-Weissler

Rachamilevitch

Aloni

et al. 2009

Planta

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“…Whilst the role of FK has been the subject of intensive recent investigation in the closely related species tomato (Solanum lycopersicum; Kanayama et al 1997, Odanaka et al 2002, German et al 2003, the profound differences in metabolism in these species (see Fernie and Willmitzer 2004 for details) led us to address the role of FK in potato. For this purpose, we generated transgenic potato plants in two cultivars of potatoRecord and Desiree that expressed StFK1 in both the sense and antisense orientation.…”

Section: Genetic Manipulation Of Stfki In Potato Plantsmentioning

confidence: 99%

Modulation of Fructokinase Activity of Potato (Solanum tuberosum) Results in Substantial Shifts in Tuber Metabolism

Davies¹,

Shepherd²,

Burrell

et al. 2005

Plant and Cell Physiology

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;Potato plants (Solanum tuberosum L. cvs Desiree and Record) transformed with sense and antisense constructs of a cDNA encoding the potato fructokinase StFK1 exhibited altered transcription of this gene, altered amount of protein and altered enzyme activities. Measurement of the maximal catalytic activity of fructokinase revealed a 2-fold variation in leaf (from 90 to 180% of wild type activity) and either a 10-or 30-fold variation in tuber (from 10 or 30% to 300% in Record and Desiree, respectively) activity. The comparative effect of the antisense construct in leaf and tuber tissue suggests that this isoform is only a minor contributor to the total fructokinase activity in the leaf but the predominant isoform in the tuber. Antisense inhibition of the fructokinase resulted in a reduced tuber yield; however, its overexpression had no impact on this parameter. The modulation of fructokinase activity had few, consistent effects on carbohydrate levels, with the exception of a general increase in glucose content in the antisense lines, suggesting that this enzyme is not important for the control of starch synthesis. However, when metabolic fluxes were estimated, it became apparent that the transgenic lines display a marked shift in metabolism, with the rate of redistribution of radiolabel to sucrose markedly affected by the activity of fructokinase. These data suggest an important role for fructokinase, acting in concert with sucrose synthase, in maintaining a balance between sucrose synthesis and degradation by a mechanism independent of that controlled by the hexose phosphate-mediated activation of sucrose phosphate synthase.

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“…Especially, fructokinase is important to regulate the level of fructose that is the primary product of sucrose and sorbitol. Kanayama et al (1997Kanayama et al ( , 1998 purified isozymes FrK1 and FrK2, isolated the cDNA of each isozyme, and showed the expression of FrK1 in 7 young fruit and FrK2 in mature fruit. Fructokinase was regulated by sugar (Kanayama et al, 1997), and controlled the fructose level in apples and Japanese pear fruit (Suzuki et al, 2001) and peach fruit .…”

Section: Metabolic Conversion Of Translocation Sugars In Fruitmentioning

confidence: 99%

“…Kanayama et al (1997Kanayama et al ( , 1998 purified isozymes FrK1 and FrK2, isolated the cDNA of each isozyme, and showed the expression of FrK1 in 7 young fruit and FrK2 in mature fruit. Fructokinase was regulated by sugar (Kanayama et al, 1997), and controlled the fructose level in apples and Japanese pear fruit (Suzuki et al, 2001) and peach fruit . ADPglucose pyrophosphorylase and starch synthase for starch generation, and phosphorylase and amylase for starch breakdown are also important for sugar accumulation and sink activity in fruits accumulating a lot of starch.…”

Section: Metabolic Conversion Of Translocation Sugars In Fruitmentioning

confidence: 99%

Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation

Yamaki

2010

J. Japan. Soc. Hort. Sci.

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Photoassimilates needed for fruit development are supplied from leaves, converted in fruit to substances relating to the specific quality of the fruit, then accumulate in the fruit. There are various regulation steps in the process from photoassimilate synthesis in leaves to sugar accumulation in fruit: photosynthesis, synthesis of translocation sugars, loading of translocation sugars, their translocation, their unloading, their membrane transport, their metabolic conversion, and compartmentation in vacuoles. Thus, it is important to clarify the mechanism and regulation of each step in fruit development. In this review, mainly the metabolic conversion of translocation sugars and their regulation at the genetic level in fruit are described because the metabolic conversion in fruit contributes greatly to produce the sink activity needed for fruit development.

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Divergent Fructokinase Genes Are Differentially Expressed in Tomato

Cited by 76 publications

References 31 publications

LeFRK2 is required for phloem and xylem differentiation and the transport of both sugar and water

LeFRK2 is required for phloem and xylem differentiation and the transport of both sugar and water

Modulation of Fructokinase Activity of Potato (Solanum tuberosum) Results in Substantial Shifts in Tuber Metabolism

Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation

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