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Mobilization of seed storage lipid by Arabidopsis seedlings is retarded in the presence of exogenous sugars.

To JP, Reiter WD, Gibson SI - BMC Plant Biol. (2002)

Bottom Line: Wild-type seedlings become insensitive to glucose inhibition of storage lipid breakdown within 3 days of the start of imbibition.This effect is not solely due to the osmotic potential of the media, as substantially higher concentrations of sorbitol than of glucose are required to exert significant effects on lipid breakdown.The inhibitory effect of glucose on lipid breakdown is limited to a narrow developmental window, suggesting that completion of some critical metabolic transition results in loss of sensitivity to the inhibitory effect of glucose on lipid breakdown.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry & Cell Biology, MS140 Rice University, 6100 Main St, Houston, TX 77005-1892, USA. jennto@email.unc.edu

ABSTRACT

Background: Soluble sugar levels must be closely regulated in germinating seeds to ensure an adequate supply of energy and building materials for the developing seedling. Studies on germinating cereal seeds indicate that production of sugars from starch is inhibited by increasing sugar levels. Although numerous studies have focused on the regulation of starch metabolism, very few studies have addressed the control of storage lipid metabolism by germinating oilseeds.

Results: Mobilization of storage lipid by germinating seeds of the model oilseed plant Arabidopsis thaliana (L.) Heynh. occurs at a greatly reduced rate in the presence of exogenous glucose or mannose, but not in the presence of equi-molar 3-O-methylglucose or sorbitol. The sugar-insensitive5-1/abscisic acid-insensitive4-101 (sis5-1/abi4-101) mutant is resistant to glucose inhibition of seed storage lipid mobilization. Wild-type seedlings become insensitive to glucose inhibition of storage lipid breakdown within 3 days of the start of imbibition.

Conclusions: Growth in the presence of exogenous glucose significantly retards mobilization of seed storage lipid in germinating seeds from wild-type Arabidopsis. This effect is not solely due to the osmotic potential of the media, as substantially higher concentrations of sorbitol than of glucose are required to exert significant effects on lipid breakdown. The inhibitory effect of glucose on lipid breakdown is limited to a narrow developmental window, suggesting that completion of some critical metabolic transition results in loss of sensitivity to the inhibitory effect of glucose on lipid breakdown.

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Early exposure to high concentrations of exogenous glucose inhibits seedling development. Seedlings shown in the left column were grown on the indicated media for 10 days. Seedlings shown in the right column were grown on minimal media supplemented with 0.03 M glucose for 3 days, transferred to the indicated media and grown for an additional 7 days prior to photographing. Red bars = 2.0 mm. Glc, glucose; Sorb, sorbitol.
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Figure 5: Early exposure to high concentrations of exogenous glucose inhibits seedling development. Seedlings shown in the left column were grown on the indicated media for 10 days. Seedlings shown in the right column were grown on minimal media supplemented with 0.03 M glucose for 3 days, transferred to the indicated media and grown for an additional 7 days prior to photographing. Red bars = 2.0 mm. Glc, glucose; Sorb, sorbitol.

Mentions: Previous work indicates that wild-type Arabidopsis seedlings become resistant to the inhibitory effects of high concentrations (0.27 to 0.33 M) of exogenous sugars on seedling development within 2 to 3 days of the start of imbibition [47]. Therefore, it was of interest to determine whether seedlings become resistant to the inhibitory effects of high sugar concentrations on seed storage lipid mobilization within the same time frame. Seeds were either sown on low (0.03 M) glucose media and then transferred after 3 days to high (0.27 M) glucose or sorbitol media, or were sown directly on high glucose or sorbitol media. As shown in Figure 5, seedlings sown directly on 0.27 M glucose exhibit little shoot development after 10 days of growth. In contrast, seedlings grown on 0.03 M glucose for 3 days and then for an additional 7 days on 0.27 M glucose produce very significant shoot systems. In fact, these plants have slightly larger average shoot systems than seedlings grown continuously on 0.03 M glucose (Figure 5). Interestingly, whereas seedlings sown directly on 0.24 M sorbitol + 0.03 M glucose produce larger shoot systems than seedlings sown directly on 0.27 M glucose, seedlings transferred to 0.24 M sorbitol + 0.03 M glucose after 3 days on 0.03 M glucose produce smaller shoot systems than seedlings transferred to 0.27 M glucose (Figure 5).


Mobilization of seed storage lipid by Arabidopsis seedlings is retarded in the presence of exogenous sugars.

To JP, Reiter WD, Gibson SI - BMC Plant Biol. (2002)

Early exposure to high concentrations of exogenous glucose inhibits seedling development. Seedlings shown in the left column were grown on the indicated media for 10 days. Seedlings shown in the right column were grown on minimal media supplemented with 0.03 M glucose for 3 days, transferred to the indicated media and grown for an additional 7 days prior to photographing. Red bars = 2.0 mm. Glc, glucose; Sorb, sorbitol.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC113751&req=5

Figure 5: Early exposure to high concentrations of exogenous glucose inhibits seedling development. Seedlings shown in the left column were grown on the indicated media for 10 days. Seedlings shown in the right column were grown on minimal media supplemented with 0.03 M glucose for 3 days, transferred to the indicated media and grown for an additional 7 days prior to photographing. Red bars = 2.0 mm. Glc, glucose; Sorb, sorbitol.
Mentions: Previous work indicates that wild-type Arabidopsis seedlings become resistant to the inhibitory effects of high concentrations (0.27 to 0.33 M) of exogenous sugars on seedling development within 2 to 3 days of the start of imbibition [47]. Therefore, it was of interest to determine whether seedlings become resistant to the inhibitory effects of high sugar concentrations on seed storage lipid mobilization within the same time frame. Seeds were either sown on low (0.03 M) glucose media and then transferred after 3 days to high (0.27 M) glucose or sorbitol media, or were sown directly on high glucose or sorbitol media. As shown in Figure 5, seedlings sown directly on 0.27 M glucose exhibit little shoot development after 10 days of growth. In contrast, seedlings grown on 0.03 M glucose for 3 days and then for an additional 7 days on 0.27 M glucose produce very significant shoot systems. In fact, these plants have slightly larger average shoot systems than seedlings grown continuously on 0.03 M glucose (Figure 5). Interestingly, whereas seedlings sown directly on 0.24 M sorbitol + 0.03 M glucose produce larger shoot systems than seedlings sown directly on 0.27 M glucose, seedlings transferred to 0.24 M sorbitol + 0.03 M glucose after 3 days on 0.03 M glucose produce smaller shoot systems than seedlings transferred to 0.27 M glucose (Figure 5).

Bottom Line: Wild-type seedlings become insensitive to glucose inhibition of storage lipid breakdown within 3 days of the start of imbibition.This effect is not solely due to the osmotic potential of the media, as substantially higher concentrations of sorbitol than of glucose are required to exert significant effects on lipid breakdown.The inhibitory effect of glucose on lipid breakdown is limited to a narrow developmental window, suggesting that completion of some critical metabolic transition results in loss of sensitivity to the inhibitory effect of glucose on lipid breakdown.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry & Cell Biology, MS140 Rice University, 6100 Main St, Houston, TX 77005-1892, USA. jennto@email.unc.edu

ABSTRACT

Background: Soluble sugar levels must be closely regulated in germinating seeds to ensure an adequate supply of energy and building materials for the developing seedling. Studies on germinating cereal seeds indicate that production of sugars from starch is inhibited by increasing sugar levels. Although numerous studies have focused on the regulation of starch metabolism, very few studies have addressed the control of storage lipid metabolism by germinating oilseeds.

Results: Mobilization of storage lipid by germinating seeds of the model oilseed plant Arabidopsis thaliana (L.) Heynh. occurs at a greatly reduced rate in the presence of exogenous glucose or mannose, but not in the presence of equi-molar 3-O-methylglucose or sorbitol. The sugar-insensitive5-1/abscisic acid-insensitive4-101 (sis5-1/abi4-101) mutant is resistant to glucose inhibition of seed storage lipid mobilization. Wild-type seedlings become insensitive to glucose inhibition of storage lipid breakdown within 3 days of the start of imbibition.

Conclusions: Growth in the presence of exogenous glucose significantly retards mobilization of seed storage lipid in germinating seeds from wild-type Arabidopsis. This effect is not solely due to the osmotic potential of the media, as substantially higher concentrations of sorbitol than of glucose are required to exert significant effects on lipid breakdown. The inhibitory effect of glucose on lipid breakdown is limited to a narrow developmental window, suggesting that completion of some critical metabolic transition results in loss of sensitivity to the inhibitory effect of glucose on lipid breakdown.

Show MeSH
Related in: MedlinePlus