Chain-length Distribution Profiles of Amylopectin Isolated from Endosperm Starch of Waxy and Low-amylose Bread Wheat (Triticum aestivum L.) Lines with Common Genetic Background

摘要

Large A-type endosperm starch granules were isolated from near-isogenic waxy and non-waxy lines and low-amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A-type starch ranged from 2.6% to 23.6%. Amylopectinwas isolated by concanavalin A (Con A) precipitation from the isolated starch. The lambda_(max) (range: 532-538 nm) and blue values at 680 nm (range: 0.026-0.037) of the iodine-amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non-waxy and low-amylose lines did not contain such long chains as amylose or extra-long chains of amylopectin affecting iodine complex properties. Chain-length distribution profiles measured by both high-performance size-exclusion chromatography (HPSEC) and high-performance anion-exchange chromatography (HPAEC) showed that the amylopectin structures of these lines were indistinguishable from each other. Extra-long chains were not detected in the amylopectins by HPSEC measurement. The side-chains measured by HPAEC were classified into four groups according to their degree of polymerization (DP), and the proportion of each group were in the following ranges: DP 6-12, 26.5-27.5%; DP 13-24, 43.6-44.1 %; DP 25-36,13.6-14.2%, and DP 37-60, 11.0-11.7%. The alleles on the Wx-D1 locus, i.e., Wx-D1a, Wx-D1d, Wx-D1f, and Wx-D1g, responsible for granule-bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine-amylopectin complex and thechain-length distribution profiles of amylopectin.