Non‐GMO potato lines with an altered starch biosynthesis pathway confer increased‐amylose and resistant starch properties

Abstract

The lack of a gene marker directly affecting starch biosynthesis in the potato tuber is documented. The absence of a 454 bp amplified fragment length polymorphism (AFLP) Solanum tuberosum fragment was identified in the wild potato species Solanum sandemanii and its absence results in a combined increased-amylose/high-sugar tuber chemotype. The trait is recessive, termed IAm (Increased Amylose) and was transferred to modern tetraploid S. tuberosum potato cultivars by marker-assisted crossing. Compared to controls, IAm plants had a larger number of stems and air exposed stolons, their tubers were smaller, elongated, and they were irregularly shaped. IAm starch had 28-59% higher amylose content than control starch, the starch granules were small and grossly misshaped, they had reduced crystallinity, swelling, and viscosity, reduced in vitro digestion rates with increased resistant starch fraction. The primary gene(s) responsible for the IAm phenotype is not known, but increased granule-associated phosphorylase (Pho1) and reduced starch synthase (SS) protein and enzyme activity in the IAm plants might explain the effects on starch structure. The data support the establishment of non-genetically modified crops with health-related slowly digestible carbohydrate.

Non‐GMO potato lines, synthesizing increased amylose and resistant starch, are mainly deficient in isoamylase debranching enzyme

“…The above-ground phenotype was not significantly different from the tuberosum controls (not shown), and again, this was different from the BC3 lines which displayed severe phenotypes with e.g. multiple aboveground stolons and stems (Krunic et al, 2017).…”

“…The apparent amylose content, as determined by iodide complexation (Table 1), documents the increased amylose content (29.0%-37.9%) as compared to control lines (19.8%-21.0%), also showed that the IAm lines in the BC4 collection were slightly higher as compared to the BC3 lines (26.3%-32.7%; Krunic et al, 2017). The chain-length distribution of amylopectin, as investigated by HPAEC-PAD, confirmed the previous data on BC3 potato lines homozygous for the IAm locus (Krunic et al, 2017) demonstrating a minor specific change in the chain-length profile (not shown). However, no significant reduction in the average chain length could be detected for the BC4 lines; the controls were in the range DP 31.9-32.8 and IAm lines ranged DP 27.8-38.4.…”

“…The starch content in the BC4 lines-IAm tubers was low and ranged 4.3%-9.5% fresh weight (FW) as compared to the control tubers which ranged 19.1%-20.5% (Table 1). The BC3 lines had lower starch content ranging 2.5%-5.6% (Krunic et al, 2017). Sugars in the BC4 IAm lines were rather high, 4.9%-14.7%, and indifferent from the BC3 lines (5.5%-13.0%, Krunic et al, 2017) compared with 1.8%-5.8% FW for the control lines.…”

“…We recently documented an AFLP fragment derived from the wild species S. sandemanii that is associated with altered starch deposition in the potato tuber (Krunic et al, 2017). The absence of the sequence was shown to result in increased amylose in the tuber starch and was termed IAm, for increased amylose.…”

Rice starch biotechnology: Rice endosperm as a model of cereal endosperms

“…These differences might be due to differences of catalytic properties of these enzymes, their relative activities among all BE isozymes and other enzymes such as SSs, and the genetic backgrounds, although biochemical reasons for these differences remain unknown. The industrial application of engineered starches with improved quality for industrial applications has also developed vigorously in various plant species . These results provide new insights into the regulatory mechanism of starch biosynthesis, new strategies for improvement of starch quality, and the possibility of exploiting engineered starches for food and other industrial uses.…”