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Expression of Cholera Toxin B Subunit in Transgenic Rice Endosperm

Oszvald, Maria, Kang, Tae-Jin, Tomoskozi, Sandor, Jenes, Barnabas, Kim, Tae-Geum, Cha, Youn-Soo, Tamas, Laszlo, Yang, Moon-Sik
Molecular biotechnology 2008 v.40 no.3 pp. 261-268
rice, Oryza sativa, DNA, polymerase chain reaction, transgenic plants, vaccines, wheat, endosperm, cholera toxin, molecular weight, introns, introduced plants
The synthetic cholera toxin B subunit (CTB) gene, modified according to the optimized codon usage of plant genes, was introduced into a plant expression vector and expressed under the control of the Bx17 HMW (high molecular weight) wheat endosperm-specific promoter containing an intron of the rice act1. The recombinant vector was transformed into rice plants using a biolistic-mediated transformation method. Stable integration of the synthetic CTB gene into the chromosomal DNA was confirmed by PCR amplification analysis. A high level of CTB (2.1% of total soluble protein) was expressed in the endosperm tissue of the transgenic rice plants. The synthetic CTB produced only in the rice endosperm demonstrated strong affinity for GM₁-ganglioside, thereby suggesting that the CTB subunits formed an active pentamer. The successful expression of CTB genes in transgenic plants makes it a powerful tool for the development of a plant-derived edible vaccine.