Genetic modification of cassava for enhanced starch production

被引:114
作者
Ihemere, Uzoma
Arias-Garzon, Diana
Lawrence, Susan
Sayre, Richard
机构
[1] Ohio State Univ, Dept Plant Cellular & Mol Biol, Columbus, OH 43210 USA
[2] Ohio State Univ, Dept Hort & Crop Sci, Columbus, OH 43210 USA
[3] BASF Plant Sci, Res Triangle Pk, NC 27709 USA
[4] BARC W, Beltsville, MD 20705 USA
关键词
ADP-glucose pyrophosphorylase; Agrobacterium-mediated transformation; starch; transgenic cassava;
D O I
10.1111/j.1467-7652.2006.00195.x
中图分类号
Q81 [生物工程学(生物技术)]; Q93 [微生物学];
学科分类号
071005 ; 0836 ; 090102 ; 100705 ;
摘要
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.
引用
收藏
页码:453 / 465
页数:13
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