Provitamin A biofortification of cassava enhances shelf life but reduces dry matter content of storage roots due to altered carbon partitioning into starch
Open Access
- 28 November 2017
- journal article
- research article
- Published by Wiley in Plant Biotechnology Journal
- Vol. 16 (6), 1186-1200
- https://doi.org/10.1111/pbi.12862
Abstract
Storage roots of cassava (Manihot esculenta Crantz), a major subsistence crop of sub-Saharan Africa, are calorie rich but deficient in essential micronutrients, including provitamin A β-carotene. In this study, β-carotene concentrations in cassava storage roots were enhanced by co-expression of transgenes for deoxy-d-xylulose-5-phosphate synthase (DXS) and bacterial phytoene synthase (crtB), mediated by the patatin-type 1 promoter. Storage roots harvested from field-grown plants accumulated carotenoids to ≤50 μg/g DW, 15- to 20-fold increases relative to roots from nontransgenic plants. Approximately 85%–90% of these carotenoids accumulated as all-trans-β-carotene, the most nutritionally efficacious carotenoid. β-Carotene-accumulating storage roots displayed delayed onset of postharvest physiological deterioration, a major constraint limiting utilization of cassava products. Large metabolite changes were detected in β-carotene-enhanced storage roots. Most significantly, an inverse correlation was observed between β-carotene and dry matter content, with reductions of 50%–60% of dry matter content in the highest carotenoid-accumulating storage roots of different cultivars. Further analysis confirmed a concomitant reduction in starch content and increased levels of total fatty acids, triacylglycerols, soluble sugars and abscisic acid. Potato engineered to co-express DXS and crtB displayed a similar correlation between β-carotene accumulation, reduced dry matter and starch content and elevated oil and soluble sugars in tubers. Transcriptome analyses revealed a reduced expression of genes involved in starch biosynthesis including ADP-glucose pyrophosphorylase genes in transgenic, carotene-accumulating cassava roots relative to nontransgenic roots. These findings highlight unintended metabolic consequences of provitamin A biofortification of starch-rich organs and point to strategies for redirecting metabolic flux to restore starch production.Funding Information
- Bill and Melinda Gates Foundation (OPPGD1484)
- U.S. Department of Agriculture (2015‐67013‐22839)
This publication has 68 references indexed in Scilit:
- Abscisic Acid Synthesis and ResponseThe Arabidopsis Book, 2013
- Retina, Retinol, Retinal and the Natural History of Vitamin A as a Light SensorNutrients, 2012
- Binding of ABI4 to a CACCG motif mediates the ABA-induced expression of the ZmSSI gene in maize (Zea mays L.) endospermJournal of Experimental Botany, 2012
- Extending Cassava Root Shelf Life via Reduction of Reactive Oxygen Species ProductionPlant Physiology, 2012
- Statistical methods on detecting differentially expressed genes for RNA-seq dataBMC Systems Biology, 2011
- β-Carotene Is an Important Vitamin A Source for HumansJournal of Nutrition, 2010
- Provitamin A Accumulation in Cassava (Manihot esculenta) Roots Driven by a Single Nucleotide Polymorphism in a Phytoene Synthase GeneTHE PLANT CELL ONLINE, 2010
- Metabolic Engineering of Potato Carotenoid Content through Tuber-Specific Overexpression of a Bacterial Mini-PathwayPLOS ONE, 2007
- The CauliflowerOrGene Encodes a DnaJ Cysteine-Rich Domain-Containing Protein That Mediates High Levels of β-Carotene AccumulationTHE PLANT CELL ONLINE, 2006
- [34] Chlorophylls and carotenoids: Pigments of photosynthetic biomembranesPublished by Elsevier BV ,1987