title: A genetic strategy generating wheat with very high amylose content.
abstract: Resistant starch (RS), a type of dietary fibre, plays an important role in human health; however, the content of RS in most modern processed starchy foods is low. Cereal starch, when structurally manipulated through a modified starch biosynthetic pathway to greatly increase the amylose content, could be an important food source of RS. Transgenic studies have previously revealed the requirement of simultaneous down-regulation of two starch branching enzyme (SBE) II isoforms both located on the long arm of chromosome 2, namely SBEIIa and SBEIIb, to elevate the amylose content in wheat from ~25% to ~75%. The current study revealed close proximity of genes encoding SBEIIa and SBEIIb isoforms in wheat with a genetic distance of 0.5 cM on chromosome 2B. A series of deletion and single nucleotide polymorphism (SNP) loss of function alleles in SBEIIa, SBEIIb or both was isolated from two different wheat populations. A breeding strategy to combine deletions and SNPs generated wheat genotypes with altered expression levels of SBEIIa and SBEIIb, elevating the amylose content to an unprecedented ~85%, with a marked concomitant increase in RS content. Biochemical assays were used to confirm the complete absence in the grain of expression of SBEIIa from all three genomes in combination with the absence of SBEIIb from one of the genomes.
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Ahmed
authors: A
authors: Regina
authors: Limagrain Cereales Ingredients, ZAC Les Portes de Riom, Riom Cedex, France.
authors: Pierre
authors: P
authors: Berbezy
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Behjat
authors: B
authors: Kosar-Hashemi
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Suzhi
authors: S
authors: Li
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Mark
authors: M
authors: Cmiel
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Oscar
authors: O
authors: Larroque
authors: CSIRO Food and Nutrition Flagship, Adelaide, SA, Australia.
authors: Anthony R
authors: AR
authors: Bird
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Steve M
authors: SM
authors: Swain
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Colin
authors: C
authors: Cavanagh
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Stephen A
authors: SA
authors: Jobling
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.
authors: Zhongyi
authors: Z
authors: Li
authors: CSIRO Agriculture Flagship, Canberra, ACT, Australia.|International Rice Research Institute, Los Banos, Philippines.
authors: Matthew
authors: M
authors: Morell
mesh_terms: D000483:Alleles; D000688:Amylose / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D003433:Crosses, Genetic; D017343:Genes, Plant / Q000235:genetics; D005819:Genetic Markers / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D014908:Triticum / Q000235:genetics* / Q000378:metabolism
chemical_list: D005819:Genetic Markers; D000688:Amylose
keywords: amylopectin; amylose; resistant starch; starch; starch branching enzyme; wheat