Expression of Escherichia coli branching enzyme in tubers of amylose‐free transgenic potato leads to an increased branching degree of the amylopectin

Abstract

SummaryIn order to increase the branching degree of potato tuber starch, the gene encoding branching enzyme (glgB) of Escherichia coil was expressed in the amylose-free potato mutant. The E. coil glgB was cloned in the binary vector pBIN19 under the transcriptional control of the potato Granule Bound Starch Synthase (GBSS) promoter and transitpeptide sequence. The E. coil glgB was cloned behind the two N-terminal amino acids of the GBSS mature protein, creating a chimeric protein. Transgenic plants were obtained which expressed the E. coil branching enzyme as was shown by the presence of mRNA and protein in the tubers. Correctly processed protein was found both in the soluble and starch granule bound protein fraction. Analysis of the starch showed an increase in the branching degree (DE) of up to 25% more branchpoints. The increase in the number of branchpoints was due to the presence of more short chains, with a degree of polymerization (DP) of 16 glucose-residues or less in the amylopectin. Changes in other characteristics of the starch, such as average chain length (CL) and ;~ax, indicated a more branched structure for starch of transformed plants as well.

Molecular characterization and biotechnological improvement of the processing quality of potatoes

“…Expression of bacterial glycogen branching enzyme in tubers of amylose-free transgenic potatoes leads to amylopectin with significantly increased branching compared with control amylopectin Á up to 25% more branch-points (Kortstee et al 1996).…”

“…Candidate genes located in the QTL regions affecting the dry matter content include two starch phosphorylase genes on chromosome I, a Rubisco gene on chromosome II, a starch synthase gene on chromosome III, a starch phosphorylase gene and a debranching enzyme gene on chromosome IX, a Rubisco activase gene and an apoplast invertase gene on chromosome X, a sucrose transporter gene on chromosome XI, and a sucrose synthase gene on chromosome XII (Chen et al 2001). Transgenic evidence for the involvement in starch dry matter has been available for several of these enzymes, including sucrose synthase (Zrenner et al 1995), starch synthase (Kuipers et al 1994), and glucan branching enzyme (Kortstee et al 1996). Some of the genes have already converted to molecular markers for markerassisted selection of dry matter content of potato tubers.…”

Eleven <i>StOSMs</i> Genes in the Potato Genome Response to Water Deficiency

“…RH was selected as a diploid model for potato genome sequencing. In this study ZHB minitubers were sown in a pot containing peat as the medium (Pindstruo Mosebrug, DK) and grown under the following conditions: water content of 70% ± 5% in the medium, light intensity of 100 µmol m -2 s -1 , temperature of 20-25°C and relative humidity of 60-80%, as it was done by Anne J.K (Anne et al, 1996, Liu et al 2012). …”

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

“…For producing starches with higher branching degree of amylopectin and novel properties, the E. coli branching enzyme (GLGB) was introduced in amylose containing background (Krohn et al, 1994) and amylose-free potato mutant (Kortstee et al, 1996). In the former a slightly higher amylopectin percentage and a small difference in granule surface morphology was observed, while the branching degree of amylopectin was 25% higher in the latter as compared to the control.…”

“…These genes may have properties that are slightly different from their plant counterparts and thus create different or novel phenotypes. An example of this is the study carried out by Kortstee et al (1996) in which Escherichia coli glycogen branching enzyme has been introduced in amylose-free potato mutant, resulting in 25% higher branching degree of amylopectin.…”