Metabolite Signals Regulate Gene Expression and Source/Sink Relations in Cereal Seedlings

Thomas, Bruce R.; Rodriguez, Raymond L.

doi:10.1104/pp.106.4.1235

Cited by 122 publications

(83 citation statements)

References 27 publications

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“…Gifford, unpublished data). The embryonic axis has also been shown to play a role in storage reserve mobilization in diverse angiosperm species such as cucumber (Cucumis sativus L.) (Davies and Chapman, 1979a, 1979b, 1980, castor bean (Xicinus communis L.) (Gifford et al, 1984;Mullen and Gifford, 1995), mung bean (Kern and Chrispeels, 1978), sunflower (Helianfkus annuus L.) (Allen et al, 1984), and barley (Hordeum vulgare L.) (Thomas and Rodriguez, 1994;Jacobsen et al, 1995). In some instances, there is hormonal regulation by the embryonic axis.…”

Section: Mobilization Of Megagametophyte Protein Reservesmentioning

confidence: 99%

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

1997

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The mobilization and utilization of the major storage proteins in loblolly pine (Pinus taeda L.) seeds following imbibition were investigated. Most of the seed protein reserves were contained within the megagametophyte. Breakdown of these proteins occurred primarily following radicle emergence and correlated with a substantial increase in the free amino acid pool i n the seedling; the majority of this increase appeared to be the result of export from the megagametophyte. The megagametophyte was able to break down storage proteins and export free amino acids i n the absence of the seedling.Arginine (Arg) was the most abundant amino acid among the principal storage proteins of the megagametophyte and was a major component of the free amino acid pools i n both the seedling and the megagametophyte. The increase in free Arg coincided with a marked increase in arginase activity, mainly localized within the cotyledons and epicotyl of the seedling. Arginase activity was negligible in isolated seedlings. Experiments with phenylphosphorodiamidate, a urease inhibitor, supported the hypothesis that arginase participates in Arg metabolism in the seedling. The results of this study indicate that Arg could play an important role i n the nutrition of loblolly pine during early seedling growth.

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Section: Mobilization Of Megagametophyte Protein Reservesmentioning

confidence: 99%

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

1997

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“…They are also major regulatory molecules that control gene expression, metabolism, physiology, cell cycle, and development in prokaryotes and eukaryotes (Newgard and McGarry, 1995;Ronne, 1995;Saier et al, 1995). In plants, it has been shown that sugars regulate the expression of a broad spectrum of genes involved in many essential processes (e.g., Sheen, 1990;Thomas and Rodriguez, 1994;Stitt and Sonnewald, 1995;Graham, 1996;Koch, 1996;Smeekens, 1998). Furthermore, sugars affect developmental and metabolic processes throughout the life cycle of the plant.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Furthermore, sugars affect developmental and metabolic processes throughout the life cycle of the plant. These processes include germination, growth, flowering, senescence, sugar metabolism, and photosynthesis (von Schaewen et al, 1990;Dickinson et al, 1991;Stitt et al, 1991; Goldschmidt and Huber, 1992; Huber and Hanson, 1992; Bernier et al, 1993; Ding et al, 1993; Yang et al, 1993;Thomas and Rodriguez, 1994; Dangl et al, 1995; Kovtun and Daie, 1995; Jang and Sheen, 1997;Perata et al, 1997;Prata et al, 1997;Smeekens and Rook, 1997; Wingler et al, 1998).Photosynthesis is regulated by sugar levels, and this regulation overrides that of light, tissue type, and developmental stage (Sheen, 1990;von Schaewen et al, 1990; Krapp et al, 1993). Increased concentrations of externally supplemented sugar or internal modification of sugar content inhibits photosynthesis and causes stunted growth of various plants (von Schaewen et al, 1990;Dickinson et al, 1991;Sonnewald et al, 1991Sonnewald et al, , 1993 Goldschmidt and Huber, 1992; Jones et al, 1996; Jang et al, 1997).…”

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confidence: 99%

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Overexpression of Arabidopsis Hexokinase in Tomato Plants Inhibits Growth, Reduces Photosynthesis, and Induces Rapid Senescence

Dai¹,

Schaffer²,

Petreikov³

et al. 1999

The Plant Cell

134

191

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Sugars are key regulatory molecules that affect diverse processes in higher plants. Hexokinase is the first enzyme in hexose metabolism and may be a sugar sensor that mediates sugar regulation. We present evidence that hexokinase is involved in sensing endogenous levels of sugars in photosynthetic tissues and that it participates in the regulation of senescence, photosynthesis, and growth in seedlings as well as in mature plants. Transgenic tomato plants overexpressing the Arabidopsis hexokinase-encoding gene AtHXK1 were produced. Independent transgenic plants carrying single copies of AtHXK1 were characterized by growth inhibition, the degree of which was found to correlate directly to the expression and activity of AtHXK1 . Reciprocal grafting experiments suggested that the inhibitory effect occurred when AtHXK1 was expressed in photosynthetic tissues. Accordingly, plants with increased AtHXK1 activity had reduced chlorophyll content in their leaves, reduced photosynthesis rates, and reduced photochemical quantum efficiency of photosystem II reaction centers compared with plants without increased AtHXK1 activity. In addition, the transgenic plants underwent rapid senescence, suggesting that hexokinase is also involved in senescence regulation. Fruit weight, starch content in young fruits, and total soluble solids in mature fruits were also reduced in the transgenic plants. The results indicate that endogenous hexokinase activity is not rate limiting for growth; rather, they support the role of hexokinase as a regulatory enzyme in photosynthetic tissues, in which it regulates photosynthesis, growth, and senescence. INTRODUCTIONSugars are central compounds in nature that serve as essential metabolic nutrients and structural components for most organisms. They are also major regulatory molecules that control gene expression, metabolism, physiology, cell cycle, and development in prokaryotes and eukaryotes (Newgard and McGarry, 1995;Ronne, 1995;Saier et al., 1995). In plants, it has been shown that sugars regulate the expression of a broad spectrum of genes involved in many essential processes (e.g., Sheen, 1990;Thomas and Rodriguez, 1994;Stitt and Sonnewald, 1995; Graham, 1996; Koch, 1996;Smeekens, 1998). Furthermore, sugars affect developmental and metabolic processes throughout the life cycle of the plant. These processes include germination, growth, flowering, senescence, sugar metabolism, and photosynthesis (von Schaewen et al., 1990;Dickinson et al., 1991;Stitt et al., 1991; Goldschmidt and Huber, 1992; Huber and Hanson, 1992; Bernier et al., 1993; Ding et al., 1993; Yang et al., 1993;Thomas and Rodriguez, 1994; Dangl et al., 1995; Kovtun and Daie, 1995; Jang and Sheen, 1997;Perata et al., 1997;Prata et al., 1997;Smeekens and Rook, 1997; Wingler et al., 1998).Photosynthesis is regulated by sugar levels, and this regulation overrides that of light, tissue type, and developmental stage (Sheen, 1990;von Schaewen et al., 1990; Krapp et al., 1993). Increased concentrations of externally supplemented sugar o...

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“…It is of particular interest that both metabolite signals (essentially sucrose) and hormonal signals (GAs and ABA) participate in controlling the total amount of expression of the amylase gene as well as the expression of different amylase genes encoding isozymes with distinet substrate speeifieities. Moreover, depletion of suerose has been shown to stimulate synthesis of GAs (Thomas & Rodriguez, 1994). Before establishing such interactions between carbon metabolite and hormonal signals for control of FFH gene expression, FEH enzymes have to be purified to homogeneity in order to raise specific antibodies and make nucleotidic probes.…”

Section: Regulation Of Fructan Exohydrolase Activitymentioning

confidence: 99%

Rise of fructan exohydrolase activity in stubble of Lolium perenne after defoliation is decreased by uniconazole, an inhibitor of the biosynthesis of gibberellins

et al. 1997

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SUMMARYThe objectives of this study were (i) to evaluate the relative involvement of fructans from leaf sheaths and from elongating leaf bases to regrowth after defoliation of Lolium perenne L. by following fructan exoh^^drolase (FEH), sucrose-sucrose fructosyl transferase (SST) and invertase (INV) activities and (ii) to examine whether gibberellins could be implicated in regulation of FEH activity. In stubble, 36 % of fructans are located in leaf bases and 64 % in leaf sheaths. During the first phase of regrowth, the depletion of carbohydrates was mainly due to the decline of fructans, which represented 76 % and 50 % of the carbohydrates mobilized from leaf sheaths and elongating leaf bases respectively. Despite a decrease in protein content, FEH activity increased 2-5-fold in leaf sheaths and sixfold in elongating leaf bases, so that the fructan-hydrolysing activity was four times higher in growing leaves than in leaf sheaths, 2 d after defoliation. INV activity also increased, whereas the pattern of SST activity was inversely related to the variations of both hydrolysing activities. SST activity, which is highest in growing leaves, declined approximately threefold in leaf sheaths and elongating leaf bases at the beginning of regrowth.The increase in activity of FEH in stubble was strongly inhibited by an inhibitor of the biosynthesis of gibberellin, uniconazole. FEH activity was decreased to c. 67 %, 45 % and 33 % of the level in nontreated plants 24, 48 and 72 h following defoliation, respectively. The inhibition could be overcome by a subsequent treatment with gibberellic acids (GAs). For the first time, data are provided to support the view that GAs might play a role in the regulation of FEH activity, and the implication of this result is discussed.

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Metabolite Signals Regulate Gene Expression and Source/Sink Relations in Cereal Seedlings

Cited by 122 publications

References 27 publications

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

Amino Acid Utilization in Seeds of Loblolly Pine during Germination and Early Seedling Growth (I. Arginine and Arginase Activity)

Overexpression of Arabidopsis Hexokinase in Tomato Plants Inhibits Growth, Reduces Photosynthesis, and Induces Rapid Senescence

Rise of fructan exohydrolase activity in stubble of Lolium perenne after defoliation is decreased by uniconazole, an inhibitor of the biosynthesis of gibberellins

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