Results (
Thai) 1:
[Copy]Copied!
plants tested (six), except Bt2 which showed a single-copyinsertion. Multiple-copy genotypes could result from insertionsat di!erent loci along the chromosomes or at thesame locus. The origin of multiplicity at a single locusremains unknown, although copy organization is eitherin tandem or as inverted repeats at a given locus (Delrolesand Gardner, 1988). The hybridization pattern inthe plants Bt5 and Bt6 was similar indicating that thesetwo plants probably arose from a single transformationevent. As expected, the non-transgenic tomato plantDNA (Fig. 2, lane C) did not show any hybridizationsignal.Double-antibody sandwich ELISA analysis was performedusing polyclonal rabbit antibodies speci"c forCry1Ac protein to detect the levels of toxin expression inthe transgenic plants. Toxin levels ranged from 0.04 to0.41% of total soluble protein (Table 1). The maximumlevel of Cry1Ac expression reported here (0.41% of thetotal soluble protein) is among the highest reported inthe literature (Schuler et al., 1998). Various plant speciestransformed with synthetic Bt genes under the control ofconstitutive promoters such as CaMV 35S exhibiteda wide range of levels of foreign protein expression. Forexample, out of total soluble protein, 0.1% of Cry3A inpotato (Adang et al., 1993), 0.03% of Cry1Ab in tobacco(Perlak et al., 1991), 0.05% of Cry1Ab in rice (Fujimotoet al., 1993), 0.4% of Cry1Ab in maize (Koziel et al., 1993)and 0.4% of Cry1Ac in canola (Stewart et al., 1996) were
observed. Recently, Cheng et al. (1998) reported extraordinary
levels of Cry1Ac expression (3% of the total
soluble protein) in transgenic rice, the maximum level of
Bt gene expression obtained to date, by nuclear transformation.
McBride et al. (1995) demonstrated an alternative
to the usage of synthetic Bt genes by engineering
a native cry1Ac into tobacco chloroplasts, yielding transgenic
plants with 3}5% of Cry1Ac protein. In another
recent report dealing with transplastomic tobacco, Kota
et al. (1999) have expressed Cry2Aa protein up to 2}3%
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