In maize, co-expression of GAT and GR79-EPSPS provides high glyphosate resistance, along with low glyphosate residues

• Published in: aBIOTECH Vol. 4; no. 4; pp. 277 - 290
• Main Authors: Li, Shengyan, Li, Pengcheng, Li, Xiangyin, Wen, Ning, Wang, Yinxiao, Lu, Wei, Lin, Min, Lang, Zhihong
• Format: Journal Article
• Language: English
• Published: Singapore Springer Nature Singapore 01.12.2023
• Subjects: Agriculture; Bioinformatics; Biomedical and Life Sciences; Life Sciences; Plant Breeding/Biotechnology; Plant Genetics and Genomics; Plant Sciences; Research Article; Low residues; Glyphosate resistance; Transgenic maize; gene; Gr79-epsps gene; Gat gene
• ISSN: 2662-1738; 2662-1738
• DOI: 10.1007/s42994-023-00114-8

Herbicide tolerance has been the dominant trait introduced during the global commercialization of genetically modified (GM) crops. Herbicide-tolerant crops, especially glyphosate-resistant crops, offer great advantages for weed management; however, despite these benefits, glyphosate-resistant maize ( Zea mays L.) has not yet been commercially deployed in China. To develop a new bio-breeding resource for glyphosate-resistant maize, we introduced a codon-optimized glyphosate N-acetyltransferase gene, gat , and the enolpyruvyl-shikimate-3-phosphate synthase gene, gr79-epsps , into the maize variety B104. We selected a genetically stable high glyphosate resistance (GR) transgenic event, designated GG2, from the transgenic maize population through screening with high doses of glyphosate. A molecular analysis demonstrated that single copy of gat and gr79-epsps were integrated into the maize genome, and these two genes were stably transcribed and translated. Field trials showed that the transgenic event GG2 could tolerate 9000 g acid equivalent (a.e.) glyphosate per ha with no effect on phenotype or yield. A gas chromatography-mass spectrometry (GC–MS) analysis revealed that, shortly after glyphosate application, the glyphosate (PMG) and aminomethylphosphonic acid (AMPA) residues in GG2 leaves decreased by more than 90% compared to their levels in HGK60 transgenic plants, which only harbored the epsps gene. Additionally, PMG and its metabolic residues (AMPA and N-acetyl-PMG) were not detected in the silage or seeds of GG2, even when far more than the recommended agricultural dose of glyphosate was applied. The co-expression of gat and gr79-epsps , therefore, confers GG2 with high GR and a low risk of herbicide residue accumulation, making this germplasm a valuable GR event in herbicide-tolerant maize breeding.