MON87403 was developed through Agrobacterium-mediated transformation of maize immature embryos from inbred line LH244 utilizing plasmid PV-ZMAP5714.

PV-ZMAP5714 contains three cassettes: one T-DNA, containing the ATHB17 expression cassette, the plasmid backbone containing the cp4 epsps selectable marker cassette, and the aadA expression cassette.

PV-ZMAP5714 employs a tandem T-DNA approach to generate marker-free plants. In this tandem T-DNA approach, a single right border and a single left border were used to achieve separate, unlinked insertion of the T-DNA as well as the cp4 epsps selectable marker gene located in the plasmid backbone.

After initial selection of transformants for glyphosate tolerance, the cp4 epsps cassette was segregated away by conventional breeding and molecular analysis was used to identify plants containing only the intended T-DNA (and not the cp4-epsps).

A detailed molecular characterization of the inserted DNA demonstrates a single, intact copy of the T-DNA insert in a single locus within the maize genome.