Structural, Physicochemical, and Pasting Properties of Starches from Potato Plants with Repressed r1-Gene

Abstract

The aim of this work was to investigate the effect on starch molecular and physicochemical properties of down regulation of the R1 protein in potato (Solanum tuberosum L. cv. "Dianella") tubers. Most prominent is a 90% suppression of the phosphate content in the isolated potato tuber starch. The amylopectin chain length distribution profile as determined by HPAEC/PAD was not affected, but the amylose content was increased in the most down-regulated plants. The pasting properties of the transgenic starch revealed a pronounced decrease in peak viscosity and increased setback viscosity as measured using a rapid Visco analyzer. The starch gels displayed an increased hardness and stickiness with a maximum at 1.7 nmol of Glc-6P mg-1 of starch compared to the control lines. At very low phosphate levels (1.4 nmol of Glc-6P mg-1 of starch), the gel hardness was decreased as a result of increased gel brittleness. The increase in gel brittleness is believed to be an effect of an increased proportion of free amylopectin blocklets in the starch as determined by SEC/RI. The possible links between the structural and physicochemical parameters are discussed.

α-Glucan, water dikinase (GWD): A plastidic enzyme with redox-regulated and coordinated catalytic activity and binding affinity

“…Starch phosphorylation is an integral part of de novo starch synthesis (4,5), and antisense repression of ␣-glucan, water dikinase (GWD) synthesis in potatoes results in a 90% reduction of starch-bound phosphate (6,7). Mutations in a homologous gene in Arabidopsis termed sex1 lead to a dramatic reduction or total suppression of the phosphate content in leaf starch (3).…”

Cloning and Sequence Analysis of the Nucleotide-Binding Domain of an Alpha-Glucan, Water Dikinase Gene from Cassava (Manihot esculenta Crantz)

“…Suppression of GWD synthesis in potato using antisense technology resulted in a 90% decrease in starch-bound phosphate (Lorberth et al, 1998;Viksø-Nielsen et al, 2001). Similarly, a mutation in a related gene in Arabidopsis, termed sex1, leads to a decrease in the phosphate content of leaf starch (Yu et al, 2001).…”

Starch meets biotechnology : in planta modification of starch composition and functionalities

“…For industrial uses, phosphate esters contribute extraordinary water-binding capacity to starch (Muhrbeck and Eliasson 1987;Wiesenborn et al 1994;Vikso-Nielsen et al 2001;Jobling 2004). Starches with high phosphate content produce clear and viscous pastes and have improved freeze-thaw stability.…”

“…Previous studies have reported the effect of the down-regulation of GWD1 on starch composition and properties (Kozlov et al, 2007;Vikso-Nielsen et al, 2001); however, these studies were conducted on a small sample size and thus strongly limiting conclusions. Therefore, further study in detail is required.…”

“…Unlike cereal starch, potato starch contains high phosphate content conferring a high swelling capacity to starch gels, which is desired in many industrial processes (Jobling, 2004;Vikso-Nielsen et al, 2001). In industry, starch is often chemically or physically modified to gain such properties; however, these modifications are expensive and frequently produce hazardous waste.…”