YieldGard™ maize

Insect-resistant maize produced by inserting the cry1Ab gene from Bacillus thuringiensis subsp. kurstaki HD-1. The genetic modification affords resistance to attack by the European corn borer (ECB), Ostrinia nubilalis.

PV-ZMBK07 and PV-ZMGT10

The transgenic maize line MON810 was genetically engineered to resist ECB by producing its own insecticide. This line was developed by introducing a synthetic version of the cry1Ab gene, isolated from the soil bacterium Bacillus thuringiensis (Bt) which was modified to enhance the expression of the Cry1Ab protein in plants, however the resulting amino acid sequence is identical to the native protein.

Molecular studies demonstrated that a single truncated copy of the cryIAb coding sequence was integrated into the corn genome along with the enhanced cauliflower mosaic virus 35S promoter (P-e35S), and the hsp 70 intron (I-Hsp70).  The nos terminator was not integrated into MON810 due to a truncation of the 3' end of the gene cassette.  Western analysis confirmed that a truncated Cry1Ab protein of approximately 91 kD (native Cry1Ab had a molecular weight of approximately 131 kD) was inserted into the genome. 

Corn event MON 810 was produced by microprojectile bombardment of embryogenic corn tissue with plasmids PVZMBK07 and PV-ZMGT10. However plasmid vector PV-ZMGT10 was not integrated into the plant genome. Further Southern blot analysis indicated that the genes for glyphosate tolerance (CP4 EPSPS) and antibiotic resistance (neo) were not transferred to line MON 810 and the absence of the CP4 EPSPS and gox gene products was also confirmed by Western blotting. The CP4 EPSPS and GOX protein encoding genes were presumed to have been inserted into the initial transformant at a separate genetic loci from the cry1Ab gene and then subsequently lost through segregation during the crossing events leading to line MON810.

Southern analysis confirms that the nptII gene (originally present in PVZMBK07 and PV-ZMGT10) is not present in MON 810.