10.1021/acs.jafc.8b04944.s001 Le Chen Le Chen Shigang Yao Shigang Yao Tao Chen Tao Chen Qin Tao Qin Tao Xiangting Xie Xiangting Xie Xiang Xiao Xiang Xiao Derong Ding Derong Ding Qin He Qin He Jian He Jian He Coexpression of Methyltransferase Gene <i>dmt50</i> and Methylene Tetrahydrofolate Reductase Gene Increases <i>Arabidopsis thaliana</i> Dicamba Resistance American Chemical Society 2019 resistance product 5- methyl-THF 5- methyl-THF herbicide dicamba-degrading strain Rhizorhabdus dicambivorans Ndbn -20. Dmt 50 mthfr DCSA Methyltransferase Gene dmt 50 Dmt 50 demethylation activity dmt 50 gene expression field application rate Methylene Tetrahydrofolate Reductase Gene Increases Arabidopsis thaliana Dicamba Resistance Dicamba 2019-01-17 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Coexpression_of_Methyltransferase_Gene_i_dmt50_i_and_Methylene_Tetrahydrofolate_Reductase_Gene_Increases_i_Arabidopsis_thaliana_i_Dicamba_Resistance/7635938 Dicamba, a broad-spectrum and highly efficient herbicide, is an excellent target herbicide for the engineering of herbicide-resistant crops. In this study, a new tetrahydrofolate (THF)-dependent dicamba methyltransferase gene, <i>dmt50</i>, was cloned from the dicamba-degrading strain <i>Rhizorhabdus dicambivorans</i> Ndbn-20. Dmt50 catalyzed the methyl transfer from dicamba to THF, generating the herbicidally inactive product 3,6-dichlorosalicylic acid (3,6-DCSA) and 5-methyl-THF. A <i>dmt50</i> transgenic <i>Arabidopsis thaliana</i> clearly showed dicamba resistance (560 g/ha, the normal field application rate). However, Dmt50 demethylation activity was inhibited by the product 5-methyl-THF. Mthfr66, encoded by the 5,10-methylene-THF reductase gene <i>mthfr66</i> could relieve the inhibition by removing 5-methyl-THF in vitro. Compared with expression of <i>dmt50</i> alone, simultaneous expression of <i>dmt50</i> and <i>mthfr66</i> further improved the dicamba resistance (1120 g/ha) of transgenic <i>A. thaliana</i>. This study provides new genes for dicamba detoxification and a strategy for the engineering of dicamba-resistant crops.