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Genetic modification of cassava for enhanced starch production.
Plant Biotechnol J. 2006 Jul; 4(4):453-65.PB

Abstract

To date, transgenic approaches to biofortify subsistence crops have been rather limited. This is particularly true for the starchy root crop cassava (Manihot esculenta Crantz). Cassava has one of the highest rates of CO(2) fixation and sucrose synthesis for any C3 plant, but rarely reaches its yield potentials in the field. It was our hypothesis that starch production in cassava tuberous roots could be increased substantially by increasing the sink strength for carbohydrate. To test this hypothesis, we generated transgenic plants with enhanced tuberous root ADP-glucose pyrophosphorylase (AGPase) activity. This was achieved by expressing a modified form of the bacterial glgC gene under the control of a Class I patatin promoter. AGPase catalyses the rate-limiting step in starch biosynthesis, and therefore the expression of a more active bacterial form of the enzyme was expected to lead to increased starch production. To facilitate maximal AGPase activity, we modified the Escherichia coli glgC gene (encoding AGPase) by site-directed mutagenesis (G336D) to reduce allosteric feedback regulation by fructose-1,6-bisphosphate. Transgenic plants (three) expressing the glgC gene had up to 70% higher AGPase activity than control plants when assayed under conditions optimal for plant and not bacterial AGPase activity. Plants having the highest AGPase activities had up to a 2.6-fold increase in total tuberous root biomass when grown under glasshouse conditions. In addition, plants with the highest tuberous root AGPase activity had significant increases in above-ground biomass, consistent with a possible reduction in feedback inhibition on photosynthetic carbon fixation. These results demonstrate that targeted modification of enzymes regulating source-sink relationships in crop plants having high carbohydrate source strengths is an effective strategy for increasing carbohydrate yields in sink tissues.

Authors+Show Affiliations

Ihemere U
Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH 43210, USA.
Arias-Garzon D
No affiliation info available
Lawrence S
No affiliation info available
Sayre R
No affiliation info available

MeSH

BiomassEscherichia coliGene Expression Regulation, PlantGenes, BacterialGenetic EngineeringGlucose-1-Phosphate AdenylyltransferaseManihotMutagenesis, Site-DirectedPlant LeavesPlant StemsPlant TubersPlants, Genetically ModifiedPromoter Regions, GeneticReverse Transcriptase Polymerase Chain ReactionStarch

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17177810

Citation

Ihemere, Uzoma, et al. "Genetic Modification of Cassava for Enhanced Starch Production." Plant Biotechnology Journal, vol. 4, no. 4, 2006, pp. 453-65.
Ihemere U, Arias-Garzon D, Lawrence S, et al. Genetic modification of cassava for enhanced starch production. Plant Biotechnol J. 2006;4(4):453-65.
Ihemere, U., Arias-Garzon, D., Lawrence, S., & Sayre, R. (2006). Genetic modification of cassava for enhanced starch production. Plant Biotechnology Journal, 4(4), 453-65.
Ihemere U, et al. Genetic Modification of Cassava for Enhanced Starch Production. Plant Biotechnol J. 2006;4(4):453-65. PubMed PMID: 17177810.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Genetic modification of cassava for enhanced starch production. AU - Ihemere,Uzoma, AU - Arias-Garzon,Diana, AU - Lawrence,Susan, AU - Sayre,Richard, PY - 2006/12/21/pubmed PY - 2007/2/3/medline PY - 2006/12/21/entrez SP - 453 EP - 65 JF - Plant biotechnology journal JO - Plant Biotechnol J VL - 4 IS - 4 N2 - To date, transgenic approaches to biofortify subsistence crops have been rather limited. This is particularly true for the starchy root crop cassava (Manihot esculenta Crantz). Cassava has one of the highest rates of CO(2) fixation and sucrose synthesis for any C3 plant, but rarely reaches its yield potentials in the field. It was our hypothesis that starch production in cassava tuberous roots could be increased substantially by increasing the sink strength for carbohydrate. To test this hypothesis, we generated transgenic plants with enhanced tuberous root ADP-glucose pyrophosphorylase (AGPase) activity. This was achieved by expressing a modified form of the bacterial glgC gene under the control of a Class I patatin promoter. AGPase catalyses the rate-limiting step in starch biosynthesis, and therefore the expression of a more active bacterial form of the enzyme was expected to lead to increased starch production. To facilitate maximal AGPase activity, we modified the Escherichia coli glgC gene (encoding AGPase) by site-directed mutagenesis (G336D) to reduce allosteric feedback regulation by fructose-1,6-bisphosphate. Transgenic plants (three) expressing the glgC gene had up to 70% higher AGPase activity than control plants when assayed under conditions optimal for plant and not bacterial AGPase activity. Plants having the highest AGPase activities had up to a 2.6-fold increase in total tuberous root biomass when grown under glasshouse conditions. In addition, plants with the highest tuberous root AGPase activity had significant increases in above-ground biomass, consistent with a possible reduction in feedback inhibition on photosynthetic carbon fixation. These results demonstrate that targeted modification of enzymes regulating source-sink relationships in crop plants having high carbohydrate source strengths is an effective strategy for increasing carbohydrate yields in sink tissues. SN - 1467-7652 UR - https://www.unboundmedicine.com/medline/citation/17177810/Genetic_modification_of_cassava_for_enhanced_starch_production_ DB - PRIME DP - Unbound Medicine ER -