Glucose and disaccharide-sensing mechanisms modulate the expression of alpha-amylase in barley embryos.
The aim of this study was to investigate the sugar-sensing processes modulating the expression of alpha-amylase in barley (Hordeum vulgaris L. var Himalaya) embryos. The results highlight the existence of independent glucose (Glc) and disaccharides sensing. Glc treatment destabilizes the alpha-amylase mRNA. Non-metabolizable disaccharides repress alpha-amylase induction, but have no effects on transcript stability. Structure-function analysis indicates that a fructose (Fru) moiety is needed for disaccharide sensing. Lactulose (beta-galactose [Gal][1-->4]Fru), palatinose (Glc[1-->6]Fru), and turanose (Glc[1-->3]Fru) are not metabolized but repress alpha-amylase. Disrupting the fructosyl moiety of lactulose and palatinose, or replacing the Fru moiety of beta-Gal[1-->4]Fru with Glc or Gal results in molecules unable to repress alpha-amylase. Comparison of the molecular requirements for sucrose transport with those for disaccharide sensing suggests that these sugars are perceived possibly at the plasma membrane level independently from sucrose transport.
Loreti
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Department of Crop Plant Biology, University of Pisa, Via Mariscoglio 34, 56124 Pisa, Italy.
Alpi
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Perata
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D015152:Blotting, Northern; D002241:Carbohydrates / Q000032:analysis / Q000502:physiology; D004187:Disaccharides / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism / Q000502:physiology*; D001467:Hordeum / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D000516:alpha-Amylases / Q000235:genetics* / Q000378:metabolism
D002241:Carbohydrates; D004187:Disaccharides; D012333:RNA, Messenger; D000516:alpha-Amylases; D005947:Glucose