Antisense downregulation of the barley limit dextrinase inhibitor modulates starch granule size distribution, starch composition and amylopectin structure

Yvonne Stahl, Steve Coates, James H. Bryce, Peter C. Morris

    Research output: Contribution to journalArticle

    45 Citations (Scopus)

    Abstract

    The barley protein limit dextrinase inhibitor (LDI), structurally related to the a-amylase/trypsin inhibitor family, is an inhibitor of the starch debranching enzyme limit dextrinase (LD). In order to investigate the function of LDI, and the consequences for starch metabolism of reduced LDI activity, transgenic barley plants designed to downregulate LDI by antisense were generated. Homozygous antisense lines with reduced LDI protein level and activity were analysed and found to have enhanced free LD activity in both developing and germinating grains. In addition the antisense lines showed unpredicted pleiotropic effects on numerous enzyme activities, for example, a- and ß-amylases and starch syntheses. Analysis of the starch showed much reduced numbers of the small B-type starch granules, as well as reduced amylose relative to amylopectin levels and reduced total starch. The chain length distribution of the amylopectin was modified with less of the longer chains (>25 units) and enhanced number of medium chains (10-15 units). These results suggest an important role for LDI and LD during starch synthesis as well as during starch breakdown.

    Original languageEnglish
    Pages (from-to)599-611
    Number of pages13
    JournalThe Plant Journal
    Volume39
    Issue number4
    DOIs
    Publication statusPublished - Aug 2004

    Keywords

    • Barley
    • Limit dextrinase
    • Limit dextrinase inhibitor
    • Starch

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