DNA insertion from pMB4:
Transcription of cry1Ab occurs from the Arabidopsis
thaliana ribulose-1,5-bisphosphate carboxylase small subunit
promoter (Rubisco SSU)* and terminates at the Nicotiana
tabacum ribulose-1,5-bisphosphate carboxylase small subunit
terminator. The nucleotide sequence of cry1Ab, originating
from Bacillus thuringiensis was codon optimized for plant
expression and encodes a 615-amino acid protein (68.9 kDa),
corresponding to the trypsin-resistant, insecticidally active core
protein, following cleavage of the 1155-amino acid native Cry1Ab
For selection during cloning, a kanamycin resistance gene cassette
was also integrated into the genome. Transcription of the neomycin
phosphotranferase II (nphII) gene starts at the
subterranean clover stunt virus (SCSV) 1 promoter. Two segments of
nptII are transcribed, with a catalase-1 intron from
Ricinus communis between the two segments and an
intervening sequence from the MB4 plasmid following the second
segment. Transcription stops at the SCSV3 terminator.
DNA insertion from pMB6:
Transcription of the cry2Ab gene occurs from the A.
thaliana Rubisco SSU promoter* and terminates at the N.
tabacum Rubisco SSU terminator. A chloroplast targeting
peptide sequence has been added before the cry2Ab sequence
to localize the translated protein to the chloroplasts. The protein
coding region of cry2Ab is derived from B.
thuringiensis ssp. kurstaki HD-1. The bacterial gene sequence
was optimized for efficient expression in plants by the removal of
polyadenylation signals, lowering of the AT content, and the
removal of destabilising sequences.
A second nphII kanamycin resistance cassette was also
integrated into the genome. Transcription also commences from the
SCSV1 promoter** and terminates at the SCSV3 terminator, which
contains a single polyadenylation signal.
* The Rubisco SSU promoter contains 1.7 kb of 5' untranslated
region of the gene.
** No enhancers present