Skip to main content
Research article - Peer-reviewed, 2014

Starch biosynthetic genes and enzymes are expressed and active in the absence of starch accumulation in sugar beet tap-root

Turesson, Helle; Andersson, Mariette; Marttila, Salla; Thulin, Ingela; Hofvander, Per

Abstract

Abstract Background: Starch is the predominant storage compound in underground plant tissues like roots and tubers. An exception is sugar beet tap-root (Beta vulgaris ssp altissima) which exclusively stores sucrose. The underlying mechanism behind this divergent storage accumulation in sugar beet is currently not fully known. From the general presence of starch in roots and tubers it could be speculated that the lack in sugar beet tap-roots would originate from deficiency in pathways leading to starch. Therefore with emphasis on starch accumulation, we studied tap-roots of sugar beet using parsnip (Pastinaca sativa) as a comparator. Results: Metabolic and structural analyses of sugar beet tap-root confirmed sucrose as the exclusive storage component. No starch granules could be detected in tap-roots of sugar beet or the wild ancestor sea beet (Beta vulgaris ssp. maritima). Analyses of parsnip showed that the main storage component was starch but tap-root tissue was also found to contain significant levels of sugars. Surprisingly, activities of four main starch biosynthetic enzymes, phosphoglucomutase, ADP-glucose pyrophosphorylase, starch synthase and starch branching enzyme, were similar in sugar beet and parsnip tap-roots. Transcriptional analysis confirmed expression of corresponding genes. Additionally, expression of genes involved in starch accumulation such as for plastidial hexose transportation and starch tuning functions could be determined in tap-roots of both plant species. Conclusion: Considering underground storage organs, sugar beet tap-root upholds a unique property in exclusively storing sucrose. Lack of starch also in the ancestor sea beet indicates an evolved trait of biological importance. Our findings in this study show that gene expression and enzymatic activity of main starch biosynthetic functions are present in sugar beet tap-root during storage accumulation. In view of this, the complete lack of starch in sugar beet tap-roots is enigmatic.

Keywords

Beta vulgaris; Pastinaca sativa; storage accumulation; carbon allocation; starch; sucrose

Published in

BMC Plant Biology
2014, volume: 14, number: 104

Authors' information

Turesson, Helle
Swedish University of Agricultural Sciences, Department of Plant Breeding
Swedish University of Agricultural Sciences, Department of Plant Breeding
Swedish University of Agricultural Sciences, Department of Plant Protection Biology
Thulin, Ingela
Solam AB
Swedish University of Agricultural Sciences, Department of Plant Breeding

UKÄ Subject classification

Agricultural Science
Genetics and Breeding
Plant Biotechnology

Publication Identifiers

DOI: https://doi.org/10.1186/1471-2229-14-104

URI (permanent link to this page)

https://res.slu.se/id/publ/56097