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Highly Efficient Expression of Escherichia coli Heat-Labile Enterotoxin B Subunit in Plants Using Potato Virus X-Based Vector

N. V. Ravin1, V. V. Kuprianov1, L. A. Zamchuk1, A. V. Kochetov2, Yu. L. Dorokhov3, J. G. Atabekov3, and K. G. Skryabin1*

1Center “Bioengineering”, Russian Academy of Sciences, pr. 60-letiya Oktyabrya 7/1, 117312 Moscow, Russia; fax: (499) 135-0571; E-mail: nravin@biengi.ac.ru

2Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, pr. Lavrentieva 10, 630090 Novosibirsk, Russia; fax: (383) 333-1278; E-mail: ak@bionet.nsc.ru

3Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 938-0601; E-mail: atabekov@genebee.msu.su

* To whom correspondence should be addressed.

Received February 28, 2008; Revision received April 14, 2008
A synthetic gene of the B-subunit of Escherichia coli heat-labile toxin, optimized for expression in plants, was designed and synthesized. The recombinant viral vector was constructed on the basis of potato virus X containing the LTB gene instead of the removed triple block of transport genes and the coat protein gene, which provides for LTB expression in plants. The vector is introduced into the plant cells during cell infiltration by agrobacteria incorporating a binary vector, the T-DNA region of which contains a cDNA copy of the recombinant viral genome. Under conditions of posttranscriptional gene silencing inhibition, the LTB yield in Nicotiana benthamiana plants is 1-2% of total soluble protein; in this case, LTB synthesized in plants forms pentameric complexes analogous to those found in the native toxin. The designed viral system of LTB transient expression can be used to obtain in plants a vaccine against enteropathogenic Escherichia coli.
KEY WORDS: plant as “biofactories”, LTB, vaccine, viral vector

DOI: 10.1134/S0006297908100064