Analyses of isoamylase gene activity in wild-type barley indicate its involvement in starch synthesis

Plant Mol Biol. 1999 Jun;40(3):431-43. doi: 10.1023/a:1006217506090.


The notion of debranching enzyme activity as a participant in starch synthesis is gaining acceptance. Inconsistent reports from mutant analyses implicate either isoamylase or pullulanase as a determinant in amylopectin formation and whether wild-type plants utilize one or the other, or both, of these debranching enzymes in starch synthesis is unclear. Recent results on the sul mutant in maize suggest that both forms of debranching enzymes might be involved in amylopectin formation. We wished to find out if isoamylase takes part in starch synthesis by comparing isoamylase gene activity under three conditions: (1) during starch accumulation in developing sink tissues; (2) during starch degradation in germinating seeds; (3) in ectopic expression after applying sucrose, a starch precursor. We isolated the gene for barley isoamylase, isol, and analysed its expression and regulation in germinating seeds, developing endosperm and vegetative tissues, and compared the isoamylase gene expression in sink tissues from three different species. Our results indicate that isoamylase gene activity is involved in starch synthesis in wild-type plants and is modulated by sucrose.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • DNA Primers / genetics
  • DNA, Complementary / genetics
  • DNA, Plant / genetics
  • Gene Expression Regulation, Developmental / drug effects
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Plant / drug effects
  • Genes, Plant*
  • Hordeum / enzymology*
  • Hordeum / genetics*
  • Hordeum / growth & development
  • Isoamylase / genetics*
  • Molecular Sequence Data
  • Sequence Homology, Amino Acid
  • Solanum tuberosum / enzymology
  • Solanum tuberosum / genetics
  • Solanum tuberosum / growth & development
  • Starch / biosynthesis*
  • Sucrose / pharmacology
  • Triticum / enzymology
  • Triticum / genetics
  • Triticum / growth & development


  • DNA Primers
  • DNA, Complementary
  • DNA, Plant
  • Sucrose
  • Starch
  • Isoamylase

Associated data

  • GENBANK/AF142588
  • GENBANK/AF142589
  • GENBANK/AF142590
  • GENBANK/AF142591