Back
Full-text
Journal article

Modification of Cassava Root Starch Phosphorylation Enhances Starch Functional Properties.

  • Wang W Institute of Molecular Plant Biology, Department of Biology, ETH Zürich, Zürich, Switzerland.
  • Hostettler CE Institute of Molecular Plant Biology, Department of Biology, ETH Zürich, Zürich, Switzerland.
  • Damberger FF Institute of Molecular Biology and Biophysics, Department of Biology, ETH Zürich, Zürich, Switzerland.
  • Kossmann J Department of Genetics, Institute for Plant Biotechnology, Stellenbosch University, Stellenbosch, South Africa.
  • Lloyd JR Department of Genetics, Institute for Plant Biotechnology, Stellenbosch University, Stellenbosch, South Africa.
  • Zeeman SC Institute of Molecular Plant Biology, Department of Biology, ETH Zürich, Zürich, Switzerland.
Show more…
  • 2018-11-15
Published in:
  • Frontiers in plant science. - 2018
Manihot esculenta Crantz
RNAi silencing
gene overexpression
glucan water dikinase (GWD)
like sex four 2 (LSF2)
starch excess 4 (SEX4)
English Cassava (Manihot esculenta Crantz) is a root crop used as a foodstuff and as a starch source in industry. Starch functional properties are influenced by many structural features including the relative amounts of the two glucan polymers amylopectin and amylose, the branched structure of amylopectin, starch granule size and the presence of covalent modifications. Starch phosphorylation, where phosphates are linked either to the C3 or C6 carbon atoms of amylopectin glucosyl residues, is a naturally occurring modification known to be important for starch remobilization. The degree of phosphorylation has been altered in several crops using biotechnological approaches to change expression of the starch-phosphorylating enzyme GLUCAN WATER DIKINASE (GWD). Interestingly, this frequently alters other structural features of starch beside its phosphate content. Here, we aimed to alter starch phosphorylation in cassava storage roots either by manipulating the expression of the starch phosphorylating or dephosphorylating enzymes. Therefore, we generated transgenic plants in which either the wild-type potato GWD (StGWD) or a redox-insensitive version of it were overexpressed. Further plants were created in which we used RNAi to silence each of the endogenous phosphoglucan phosphatase genes STARCH EXCESS 4 (MeSEX4) and LIKE SEX4 2 (MeLSF), previously discovered by analyzing leaf starch metabolism in the model species Arabidopsis thaliana. Overexpressing the potato GWD gene (StGWD), which specifically phosphorylates the C6 position, increased the total starch-bound phosphate content at both the C6 and the C3 positions. Silencing endogenous LSF2 gene (MeLSF2), which specifically dephosphorylates the C3 position, increased the ratio of C3:C6 phosphorylation, showing that its function is conserved in storage tissues. In both cases, other structural features of starch (amylopectin structure, amylose content and starch granule size) were unaltered. This allowed us to directly relate the physicochemical properties of the starch to its phosphate content or phosphorylation pattern. Starch swelling power and paste clarity were specifically influenced by total phosphate content. However, phosphate position did not significantly influence starch functional properties. In conclusion, biotechnological manipulation of starch phosphorylation can specifically alter certain cassava storage root starch properties, potentially increasing its value in food and non-food industries.
Language
  • English
Open access status
gold
Identifiers
Persistent URL
https://sonar.ch/global/documents/36857
Statistics
Document views: 46 File downloads:
  • Full-text: 0