Effects of Homoeologous Wheat Starch Synthase IIa Genes on Starch Properties

Abstract

Near-isogenic lines (NILs) of the eight haplotypes of starch synthase IIa (SSIIa) were used to analyze the effects of SSIIa gene dosage on branch chain length, gelatinization, pasting, retrogradation, and enzymatic hydrolysis of starches. Compared to wild-type, the amylopectin of lines missing one or more active SSIIa enzymes had increases in the proportion of short branch chains (DP6-10) and decreases in midlength chains (DP11-24), and the size of these differences depended on the dosage of active SSIIa enzymes. Of the three loci, SSIIa-A1 had the smallest contribution to amylopectin structure and SSIIa-B1 the largest. The different effects of the three SSIIa enzymes on starch properties were also seen in gelatinization, retrogradation, pasting, and enzymatic hydrolysis properties. Such differences in starch properties might be useful in influencing the texture and shelf life of food products.

Novel mutant alleles of the starch synthesis gene TaSSIVb-D result in the reduction of starch granule number per chloroplast in wheat

“…For example, of the three SSIIa genes, SSIIa on the B genome has the largest contribution to amylopectin structure than those on the other two genomes [43]. Each waxy gene encoding GBSSI has different effects on amylopecitin characteristics [37, 44, 45].…”

Nutritional and Quality Traits of Pasta Made from SSIIa Null High‐Amylose Durum Wheat

“…As previously demonstrated (Hogg et al 2013), the elimination of SSIIa in durum wheat by mutations found or created in the ssIIa‐A and ssIIa‐B genes results in seeds with a high amylose content. The elimination of this key starch biosynthetic enzyme in cereal grains results in a reduction in starch, which gives the seed a wrinkled appearance and reduced seed weight and size (Yamamori et al 2000; Morell et al 2003; Konik‐Rose et al 2007; Shimbata et al 2012; Hogg et al 2013). As a result of decreased seed size and starch content, there is a significant increase in protein content (Konik‐Rose et al 2007).…”

Novel ssIIa Alleles Produce Specific Seed Amylose Levels in Hexaploid Wheat

“…Increases in wheat amylose content have also been achieved by combining natural or induced mutations of starch synthase IIa ( ssIIa ), producing bread and durum wheat with starch amylose content ranging from 35 to 48% (Yamamori et al 2000; Konik‐Rose et al 2007; Lafiandra et al 2010; Shimbata et al 2012; Hogg et al 2013; Rakszegi et al 2015; Botticella et al 2016), and mutant ssIIa lines in barley had amylose between 35 and 70% (Morell et al 2003; Sparla et al 2014). As with the sbeIIa and sbeIIa / b null lines, similar pleiotropic effects are seen in ssIIa null lines with deformed starch granules, reduced starch content and individual kernel weight, reduced flour swelling, and increased grain protein and RS.…”

“…Flours from high‐amylose ssIIa null lines also have altered starch pasting properties, seen as reduced RVA peak, trough, and final viscosity (Yamamori et al 2006; Konik‐Rose et al 2007; Rakszegi et al 2015). Unlike starch from high‐amylose maize or wheat owing to loss of SBEII function, which has a high gelatinization temperature compared with normal starch (Liu et al 2012; Hazard et al 2015), starch from ssIIa null lines has a lower gelatinization temperature (Yamamori et al 2000; Morita et al 2002; Konik‐Rose et al 2007; Shimbata et al 2012; Hogg et al 2013). When flour from ssIIa null lines was used to make bread, the loaves had inferior dough properties, decreased loaf volume, and increased firmness (Morita et al 2002; Van Hung et al 2005), all of which are generally viewed as negative bread traits.…”