Sink Metabolism in Tomato Fruit

Robinson, Nina L.; Hewitt, John D.; Bennett, A. B.

doi:10.1104/pp.87.3.727

Cited by 110 publications

(50 citation statements)

References 6 publications

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“…Fruit growth in vitro also displays a similar growth pattern to that on intact plants (27). The in vitro cultured fruit is limited in size; however, ripening, color, and flavor are normal (24), indicating that the in vitro cultured fruit may serve as a simplified source-sink system useful as a model to study tomato sink activity.…”

Section: Discussionmentioning

confidence: 79%

Light Regulation of Sink Metabolism in Tomato Fruit

Guan¹,

Janes²

1991

Plant Physiol.

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Light/dark effects on growth and sugar accumulation in tomato (Lycoperskon esculentum) fruit during early development were studied on intact plants (In vivo) and in tissue culture (in vitro).Through the use of an in vitro culture of tomato fruit, it was possible to investigate the direct effects of light on sink metabolism by eliminating the source tissue. Similar growth patterns were found in vivo and in vitro. Fruit growth in different sugars indicated that sucrose was the best source of carbon for in vitro fruit growth. Fruit growth increased as sucrose concentration increased up to 8%. Darkening the fruit decreased fruit dry weight about 40% in vivo and in vitro. The differences in the CO2 exchange rate between light and dark grown fruit indicated that light stimulation of fruit growth was due to mechanisms other than photosynthesis. Supporting this conclusion was the fact that light intensities ranging from 40 to 160 micromoles per square meter per second had no significant influence on fruit growth, and light did not increase growth of fruit cultured with glucose or fructose as a carbon source. However, light stimulated fruit growth significantly when sucrose was used as the carbon source. Light-grown fruit took up 30% more sucrose from the same source and accumulated almost twice as much hexose and starch as dark-grown fruit. A possible expansion of an additional sink for carbon by light stimulation of starch synthesis during early development will be discussed.Assimilate partitioning and translocation are major determinants of crop yield. It has been suggested (7) that the regulation of these processes is at least partially through the metabolic activity of the sink tissue. As an example of this, it has been shown that in tomato (Lycopersicon esculentum), sucrose uptake can be manipulated by altering sink metabolism through an increase or decrease in temperature (5, 31). Furthermore, this type of research illustrates the potential usefulness of identifying and studying environmental factors influencing sink activity. From a practical standpoint, such information provides a basis for plant growth and environmental control models (1, 8, 18) increasingly used by greenhouse producers for regulating crop timing and yield. However, it also provides a point of attack in our quest to understand what "sink activity" actually means in biochemical terms.

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Section: Discussionmentioning

confidence: 79%

Light Regulation of Sink Metabolism in Tomato Fruit

Guan¹,

Janes²

1991

Plant Physiol.

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“…Suc synthase is often associated with SUC cleavage in starch metabolism (Quick and Schaffer, 1996) (Fig. l), and its activity pattern (but not that of invertase) follows the transient starch accumulation pattern of tomato fruit (Robinson et al, 1988). SUC synthase activity has accordThis research was partially supported by grant no.…”

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confidence: 99%

“…The enzyme ADP-Glc PPase catalyzes the synthesis of ADP-Glc in starch-synthesizing tissue. Robinson et al (1988) reported that its activity, too, follows the transient starch accumulation pattern, although this loss of activity was not observed by Guan and Janes (1991). The other enzymes in the Suc-to-starch metabolic pathway during the transient starch accumulation period have not yet to our knowledge been studied, nor have their relative activities been compared.…”

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confidence: 99%

“…Regarding starch breakdown metabolism, Robinson et al (1988) studied developmental changes in amylase and starch phosphorylase activity in developing tomato fruit. They reported that phosphorylase activity was overwhelmingly dominant and presumably responsible for starch breakdown throughout the development of the fruit, and that neither enzyme underwent developmental modulation of activity.…”

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Sucrose-to-Starch Metabolism in Tomato Fruit Undergoing Transient Starch Accumulation

1997

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lmmature green tomato (Lycopersicon esculenfum) fruits undergo a period of transient starch accumulation characterized by developmental changes in the activities of key enzymes in the sucrose (Suc)-to-starch metabolic pathway. Activities of Suc synthase, fructokinase, ADP-glucose (Clc) pyrophosphorylase, and soluble and insoluble starch synthases decline dramatically in parallel to the decrease i n starch levels in the developing fruit. Comparison of "maximal" i n vitro activities of the enzymes in the Suc-to-starch pathway suggests that these same enzymes are limiting to the rate of starch accumulation. In contrast, activities of invertase, UDP-Clc pyrophosphorylase, nucleoside diphosphate kinase, phosphoglucoisomerase, and phosphoglucomutase do not exhibit dramatic decreases in activity and appear to be in excess of starch accumulation rates. Starch accumulation is spatially localized in the inner and radial pericarp and columella, whereas the outer pericarp and seed locule contain little starch. The seed locule is characterized by lower activities of Suc synthase, UDP-Clc pyrophosphorylase, phosphoglucomutase, ADP-Clc pyrophosphorylase, and soluble and insoluble starch synthases. The outer pericarp exhibits comparatively lower activities of ADP-Clc pyrophosphorylase and insoluble starch synthase only. These data are discussed in terms of the developmental and tissue-specific coordinated control of Suc-to-starch metabolism.

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“…A comparison of tomato genotypes differing in total fruit solids content showed a positive correlation between the final levels of soluble sugars and the peak levels of starch early in fruit development (Dinar and Stevens, 1981). The latter is regulated by the starch biosynthetic capacity, as determined by levels of AGP activity rather than starch degradative capacity (Robinson et al, 1988). In view of this relationship, AGP may be an attractive biotechnological target for increasing the soluble solids content of tomato fruit.…”

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Multiple Forms of ADP-Glucose Pyrophosphorylase from Tomato Fruit

Chen

Janes

1997

Plant Physiology

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ADP-glucose pyrophosphorylase (ACP) was purified from tomato (Lycopersicon esculentum Mill.) fruit to apparent homogeneity. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis the enzyme migrated as two close bands with molecular weights of 50,000 and 51,000. Two-dimensional polyacrylamide gel electrophoresis analysis of the purified enzyme, however, revealed at least five major protein spots that could be distinguished by their slight differences i n net charge and molecular weight. Whereas all of the spots were recognized by the antiserum raised against tomato fruit ACP holoenzyme, only three of them reacted strongly with the antiserum raised against the potato tuber ACP large subunit, and the other two spots (with lower molecular weights) reacted specifically with antisera raised against spinach leaf ACP holoenzyme and the potato tuber ACP small subunit. l h e results suggest the existente of at least three isoforms of the ACP large subunit and two isoforms of the small subunit in tomato fruit in vivo. The native molecular mass of the enzyme determined by gel filtration was 220 f 1 O kD, indicating a tetrameric structure for ACP from tomato fruit. l h e purified enzyme is very sensitive to 3-phosphoglycerate/ inorganic phosphate regulation.

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Sink Metabolism in Tomato Fruit

Cited by 110 publications

References 6 publications

Light Regulation of Sink Metabolism in Tomato Fruit

Light Regulation of Sink Metabolism in Tomato Fruit

Sucrose-to-Starch Metabolism in Tomato Fruit Undergoing Transient Starch Accumulation

Multiple Forms of ADP-Glucose Pyrophosphorylase from Tomato Fruit

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