Effect of Water Stress on the Carbohydrate Metabolism of <i>Citrullus lanatus</i> Seeds during Germination

Botha, Frederik C.; Small, J.G.C.

doi:10.1104/pp.77.1.79

Cited by 21 publications

(9 citation statements)

References 18 publications

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“…1), the ratio between the PFP isoforms also changes. These changes coincide with dramatic alterations in the metabolism from a primarily glycolytic function prior to radicle protrusion, to a gluconeogenic function during early seedling growth (10,27), and finally to a photosynthetic function. The highest specific PFP activity in the cotyledons occurs at the peak in gluconeogenesis, which is similar to castor bean endosperm PFP (21).…”

Section: Discussionmentioning

confidence: 99%

“…Matsumura and Nakai (colocynth or bitter melon) were obtained and stored as previously described (10). The different tissues of C. lanatus plants were obtained from plants grown in a glass house.…”

Section: Materials and Methods Materialsmentioning

confidence: 99%

“…Seeds were soaked in distilled water for 4 h at room temperature before the outer seed structures (seed coat and underlying seed membrane) were removed as previously de-scribed (10). The at a flow rate of 1 ml min-'.…”

Section: Germinationmentioning

confidence: 99%

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Pyrophosphate Dependent Phosphofructokinase of Citrullus lanatus: Molecular Forms and Expression of Subunits

Botha

Botha²

1991

Plant Physiol.

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During germination and seedling establishment, the total pyrophosphate-dependent phosphofructokinase (PFP) activity in the cotyledons increases. Two types of subunits with molecular weights of 68 (a-subunit) and 65 (,-subunit) kilodaltons are present. The increase in activity coincides with an approximately 10-fold increase in #-subunit and twofold increase in a-subunit content. Different isoforms of PFP are present at all stages of incubation, but the ratio between the isoforms significantly changes. A linear relationship exists between the ratio of the two PFP subunits and the ratio of the two isoforms of the enzyme. The more anionic (peak 2) isoform of the enzyme apparently is favored by a high ratio of total #-subunit to a-subunit content.The is-to a-subunit ratio of the peak 2 isoform is also approximately fivefold higher than that of the peak 1 (less anionic) isoform. It is evident that the two subunits are not coordinately expressed and the level of expression of each subunit appears to be the primary factor determining the molecular form in which the enzyme is present. In some tissues, only the 65 kilodalton polypeptide is expressed in large amounts. The peak I isoform has a higher affinity for pyrophosphate than the peak 2 isoform, while the affinity for fructose-6-phosphate is similar. Both molecular forms are activated by fructose-2,6-bisphosphate.In addition to the ATP-dependent phosphofructokinase, plants also contain a pyrophosphate-dependent phosphofructokinase, PFP,2 that catalyzes the conversion of Fru-6-P to Fru-2,6-P2 in the cytosol. Since the discovery in 1979 of PFP in pineapple leaves (14), significant levels of this enzyme have been found in a variety of plant tissues (1,3,4,11,17,21,23,24,28,29,33).Although the kinetic properties of PFP from several plant species have been studied (4,8,11,19,(24)(25)(26)28) 2Abbreviations: PFP, PPi:D-fructose-6-phosphate 1-phosphotransferase (EC 2.7.1.90); Fru-6-P, fructose-6-phosphate; Fru-2,6-P2, fructose-2,6-bisphosphate; IgG, immunoglobulin.In several species, increased PFP activity is associated with the tissues in which a net sucrose breakdown occurs (32 and references therein). In certain tissues, like castor bean endosperm (21) and the cotyledons of Citrullus lanatus (7), however, maximum PFP activity during germination coincides with the peak in gluconeogenesis. Whether these changes in PFP activity during specific physiological conditions (6, 1 1, 17, 21, 32) are due to activation of existing enzyme or to induced gene expression is unclear.The increase in PFP activity during germination in the cotyledons of C. lanatus is due to an increase in the PFP concentration (7), presumably by increased gene expression. However, interconversion between different molecular forms, as was reported for the PFP from pea (31) and potato (20), might also contribute to changes in PFP activity. In the latter studies, it was shown that PFP can be reversibly converted from a high to a low molecular form depending on the presence of 31). The enzyme from potato...

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Section: Discussionmentioning

confidence: 99%

Section: Materials and Methods Materialsmentioning

confidence: 99%

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Pyrophosphate Dependent Phosphofructokinase of Citrullus lanatus: Molecular Forms and Expression of Subunits

Botha

Botha²

1991

Plant Physiol.

Self Cite

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“…Barlow (1986) [92] showed that much of the sugar accumulation, which began with the first indication of suppression in leaf elongation under water stress in wheat, was due to glucose, fructose and sucrose. The inhibition of germination of Citrullus lanatus seeds by water stress was investigated by [93], who observed a marked effect on carbohydrate metabolism. Smaller changes in glucose content and in the reducing substance content of the control seeds occurred during germination, coinciding with a decrease in sucrose.…”

Section: Carbohydrates Changes Referencesmentioning

confidence: 99%

Plant Water-Stress Response Mechanisms

Akinci¹,

Lösel²

2012

Water Stress

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“…4e). A similar decrease in fructose has been reported in germinating watermelon seeds, but the mechanism by which this decrease occurs is still unknown [19]. In contrast, in the shoots, the amounts of the three sugars increased significantly from stage 1 to 2 and/or stage 2 to 3 ( Fig.…”

Section: Discussionmentioning

confidence: 56%

The carbohydrate catabolism of Zostera marina influenced by lower salinity during the pre-germination stage

Sugiura

Hiroe²,

Suzuki

et al. 2009

Fish Sci

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The distribution of starch granules in ungerminated seeds of Zostera marina was examined by electron microscopy and histochemistry. Quantitative changes during germination in starch and sugars [glucose/maltosaccharides (MS), sucrose, and fructose] were examined in the seeds using biochemical methods. At natural seawater salinity (30.2 psu), the number of starch granules and the amount of starch markedly decreased, resulting in no increase in the sugar content in the embryos during the early germination stage. A substantial increase in sugars in the shoots occurred after the development of true leaves, probably due to photosynthetic activity in the green true leaves. At natural seawater salinity, the amount of starch did not significantly change during the initial 14 days of germination. In contrast, at lower salinities, starch levels decreased significantly from day 0 to day 6, resulting in higher levels of glucose/MS and fructose in the basal hypocotyls. These results suggest that compared with the salinity of natural seawater, lower salinity may interfere with starch catabolism in seeds, thereby causing the seed coat to break open earlier.

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Effect of Water Stress on the Carbohydrate Metabolism of Citrullus lanatus Seeds during Germination

Cited by 21 publications

References 18 publications

Pyrophosphate Dependent Phosphofructokinase of Citrullus lanatus: Molecular Forms and Expression of Subunits

Pyrophosphate Dependent Phosphofructokinase of Citrullus lanatus: Molecular Forms and Expression of Subunits

Plant Water-Stress Response Mechanisms

The carbohydrate catabolism of Zostera marina influenced by lower salinity during the pre-germination stage

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