• Open Access

Expression of an engineered granule-bound Escherichia coli glycogen branching enzyme in potato results in severe morphological changes in starch granules

Authors

  • Xing-Feng Huang,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
    2. Graduate School Experimental Plant Sciences, Wageningen University, Wageningen, the Netherlands
    Current affiliation:
    1. Center for Rhizosphere Biology, Department of Horticulture and Landscape Architecture, Colorado State University, Fort Collins, CO, USA
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    • These authors contributed equally to this study.

  • Farhad Nazarian-Firouzabadi,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
    Current affiliation:
    1. Agronomy and plant breeding group, Faculty of Agriculture, University of Lorestan, Khorramabad, Iran
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    • These authors contributed equally to this study.

  • Jean-Paul Vincken,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
    Current affiliation:
    1. Laboratory of Food Chemistry, Wageningen University, Wageningen, the Netherlands
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  • Qin Ji,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
    Current affiliation:
    1. Department of Biology, Huaiyin Teachers College, Huaian, China
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  • Luc C. J. M. Suurs,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
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  • Richard G. F. Visser,

    1. Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
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  • Luisa M. Trindade

    Corresponding author
    • Wageningen UR – Plant Breeding, Wageningen University and Research Center, Wageningen, the Netherlands
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Correspondence (Tel +31(0)317482127; fax +31(0)317483457; email luisa.trindade@wur.nl)

Summary

The Escherichia coli glycogen branching enzyme (GLGB) was fused to either the C- or N-terminus of a starch-binding domain (SBD) and expressed in two potato genetic backgrounds: the amylose-free mutant (amf) and an amylose-containing line (Kardal). Regardless of background or construct used, a large amount of GLGB/SBD fusion protein was accumulated inside the starch granules, however, without an increase in branching. The presence of GLGB/SBD fusion proteins resulted in altered morphology of the starch granules in both genetic backgrounds. In the amf genetic background, the starch granules showed both amalgamated granules and porous starch granules, whereas in Kardal background, the starch granules showed an irregular rough surface. The altered starch granules in both amf and Kardal backgrounds were visible from the initial stage of potato tuber development. High-throughput transcriptomic analysis showed that expression of GLGB/SBD fusion protein in potato tubers did not affect the expression level of most genes directly involved in the starch biosynthesis except for the up-regulation of a beta-amylase gene in Kardal background. The beta-amylase protein could be responsible for the degradation of the extra branches potentially introduced by GLGB.

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