YieldGard™ maize

Insect-resistant and herbicide tolerant maize produced by inserting the cry1Ab gene from Bacillus thuringiensis subsp. kurstaki to confer resistance to the European corn borer (Ostrinia nubilalis), and the phosphinothricin N-acetyltransferase (PAT) encoding gene from Streptomyces viridochromogenes to confer tolerance to phosphinothricin (PPT) herbicide, specifically glufosinate ammonium.

pZO1502 Derived from pUC18

Maize line Bt11 was genetically modified to contain two novel genes, cry1Ab and pat, for insect and herbicide tolerance respectively. Both genes were introduced into a maize line by particle acceleration (biolistic) transformation.

Information on the inserted DNA sequences:
- 35S promoters derived from cauliflower mosaic virus (CaMV) and 35S-1 originated from the CM1841 isolate of CaMV as a 500 Ddel to Ddel fragment, subsequently converted to Sacl sites and 35S-2 originated from the Cabb-S strain of CaMV as a n Alul to Ddel fragments (ca 425bp), whose ends were subsequently modified.
- introns derived from the maize alcohol dehydrogenase 1S gene and were used to enhance heterologous gene expression.
- Btk gene which is an altered version of the full length cry1A(b) gene of Bacillus thuringiensis var kurstaki HD-1. The Btk was obtained as a 1.8kb Nco-Bg/ll fragment. The truncated Btk protein is identical to the N-terminal 615 amino acids of the native Btk protein of 1155 amino acids.
- pat gene (phosphinotricin acetyl transferase) cloned from the soil microorganism, Streptomyces viridochromogenes strain Tu494.  Alteration did not result in any amino acid sequence changes.
- nos terminator consisting of 423-678 of the nopaline synthase gene of Agrobacterium tumefaciens plus added restriction sites.

Vector information
Plasmid pZO1502 is the vector used for the transformation of Bt maize.  This is a derivative of plasmid pUC18. The plasmid has a molecular weight of 2.7 kb and contains the following sequences:
- the prokaryotic gene bla (also called ampR) under a procaryotic promoter encoding β-lactamase, which confers resistance to ampicillin; it is used as a bacterial selectable marker; 
- the gene lac Z, encoding a portion of a β-galactosidase, this gene is not functional;
- the pUC origin of replication derived from the plasmid pBR 322 carrying a mutation.