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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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Seedlings carrying the sis5-1/abi4-101 mutation are resistant to the inhibitory effects of exogenous glucose on mobilization of seed storage lipids. Eicosenoic (20:1) fatty acid levels were measured in mutant and wild-type seeds/seedlings harvested from the indicated media at different times after the start of imbibition. Results presented are means ± SD (n = 3). This experiment was repeated, with similar results.
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Figure 7: Seedlings carrying the sis5-1/abi4-101 mutation are resistant to the inhibitory effects of exogenous glucose on mobilization of seed storage lipids. Eicosenoic (20:1) fatty acid levels were measured in mutant and wild-type seeds/seedlings harvested from the indicated media at different times after the start of imbibition. Results presented are means ± SD (n = 3). This experiment was repeated, with similar results.

Mentions: Several groups of Arabidopsis mutants that are resistant to the inhibitory effects of high concentrations of exogenous glucose or sucrose on early seedling development have been isolated [46-50]. A representative sugar-insensitive (sis) mutant, the sis5-1/abi4-101 mutant, was analyzed to determine whether mutants of this type can also exhibit altered responses to the effects of exogenous glucose on lipid metabolism. As shown in Figure 7, sis5-1/abi4-101 seedlings metabolize significantly more 20:1 fatty acid than wild-type plants when grown on media containing 0.11 M glucose. In contrast, mutant and wild-type plants metabolize similar amounts of 20:1 fatty acid when grown on 0.11 M sorbitol (Figure 7).


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)

Seedlings carrying the sis5-1/abi4-101 mutation are resistant to the inhibitory effects of exogenous glucose on mobilization of seed storage lipids. Eicosenoic (20:1) fatty acid levels were measured in mutant and wild-type seeds/seedlings harvested from the indicated media at different times after the start of imbibition. Results presented are means ± SD (n = 3). This experiment was repeated, with similar results.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 7: Seedlings carrying the sis5-1/abi4-101 mutation are resistant to the inhibitory effects of exogenous glucose on mobilization of seed storage lipids. Eicosenoic (20:1) fatty acid levels were measured in mutant and wild-type seeds/seedlings harvested from the indicated media at different times after the start of imbibition. Results presented are means ± SD (n = 3). This experiment was repeated, with similar results.
Mentions: Several groups of Arabidopsis mutants that are resistant to the inhibitory effects of high concentrations of exogenous glucose or sucrose on early seedling development have been isolated [46-50]. A representative sugar-insensitive (sis) mutant, the sis5-1/abi4-101 mutant, was analyzed to determine whether mutants of this type can also exhibit altered responses to the effects of exogenous glucose on lipid metabolism. As shown in Figure 7, sis5-1/abi4-101 seedlings metabolize significantly more 20:1 fatty acid than wild-type plants when grown on media containing 0.11 M glucose. In contrast, mutant and wild-type plants metabolize similar amounts of 20:1 fatty acid when grown on 0.11 M sorbitol (Figure 7).

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