Description:
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Herbicide-tolerant maize MON80616 is tolerant to protoporphyrinogen IX oxidase (PPO) inhibiting herbicides. MON80616 contains a PPO gene (HN90 PPO) from _Enterobacter cloacae that expresses a PPO protein that is insensitive to PPO-inhibiting herbicides and thus confers tolerance to these herbicides.
MON80616 maize was produced by Agrobacterium tumefaciens-mediated transformation of maize tissue using the transfer DNA (T-DNA) transformation plasmid vector PV-ZMHT530724.
The T-DNA that was inserted initially contained H_N90 PPO, a cp4 epsps selectable marker, Cpf1(Cas12a) and a gRNA cassette. The Cpf1(Cas12a) and gRNA cassettes were included in the T-DNA to enable site-directed integration (SDI) of the T-DNA into a specific location in the genome through non-homologous end joining (NHEJ).
The cp4 epsps selectable marker, Cpf1(Cas12a), and gRNA cassettes were flanked by two targeting sequences called loxP sites that allow for Cre recombinase-mediated excision. Transformed lines were screened to identify a line with an integrated T-DNA at the desired genome location. The cp4 epsps selectable marker, Cpf1(Cas12a), and gRNA cassettes were then excised by crossing the chosen line with a Cre recombinase-expressing maize line. Subsequently, segregation, selection, and screening were used to isolate plants that contained the H_N90 PPO expression cassette and lacked the cp4 epsps selectable marker cassette, Cpf1(Cas12a) cassette and gRNA cassette, and any sequences from the T-DNA of the Cre recombinase-expressing maize line.
Source: USDA APHIS
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Links regarding to this GMO:
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USDA APHIS https://www.aphis.usda.gov/brs/pdf/rsr/23-208-01rsr.pdf
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Transformation / Modification technique:
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CRISPR/Cas; Agrobacterium-induced
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