Modification of potato starch granule structure and morphology in planta by expression of starch binding domain fusion proteins

X. Huang

Research output: Thesisinternal PhD, WU

Abstract

Producing starches with altered composition, structure and novel physico-chemical properties in planta by manipulating the enzymes which are involved in starch metabolism or (over)expressing heterologous enzymes has huge advantages such as broadening the range of starch applications and reducing the costs of the post-harvest starch modification. The starch binding domain (SBD) technology has been extensively explored in our lab for modifying starch in planta and producing so-called “tailored starches”. In this thesis, two different microbial enzymes, E. coli glycogen branching enzyme (GlgB) and Neisseria polysaccharea amylosucrase, were chosen and expressed in potato to modify starch composition or structure by fusing with an SBD. Expression of these different fusion proteins in potato resulted in starch granule morphology and structure alteration severely in different ways. Moreover, expression of SBD-amylosucrase fusion protein in the amylose-containing potato resulted in starch granules with a rough surface, a 2-fold increase in median granule size, and altered physico-chemical properties including higher end viscosity and higher enzymatic digestibility. Furthermore, earlier produced MAT/SBD transformants were analyzed at the transcriptional level using the POCI array. It showed that although expression of MAT in potato resulted in amalgamated starch granules, it did not affect the transcript level of other genes in the starch biosynthetic pathway. Next to these experiments, a tandem CBM25 domain of amylase from Microbacterium aurum was introduced in potato and the results suggested that it can be used as a novel tool for targeting proteins to granules during starch biosynthesis without causing side-effects. All these studies in this thesis demonstrated that the feasibility of modification of starch in planta by expression of heterologous enzymes fused with SBD.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Visser, Richard, Promotor
  • Trindade, Luisa, Co-promotor
Award date29 Nov 2010
Place of Publication[S.l.]
Print ISBNs9789085858119
Publication statusPublished - 2010

Keywords

  • solanum tuberosum
  • starch granules
  • potato starch
  • binding proteins
  • gene expression
  • transformation
  • transgenic plants
  • molecular breeding
  • in vivo experimentation

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