D. sophia is one of the most notorious broadleaf weed in China, and has evolved extremely high resistance to ALS-inhibiting herbicide tribenuron-methyl. The metabolic resistance mechanisms mediated by cytochrome P450 in D. sophia were confirmed by P450 inhibitor, RNA-sequencing, liquid chromatography-mass spectrometry (LC-MS) and RT-qPCR analysis. The P450 inhibitor malathion significantly reversed D. sophia resistance to tribenuron-methyl with the resistance index (RI) decreasing from 116 to 28. Up-regulation of four P450s (CYP96A146, CYP96A147, CYP96A15-like, CYP71A1-like), three GTs and one ABC transporter were identified and confirmed in resistant (R) D. sophia by RNA-Seq and qPCR. The LC-MS analysis demonstrated the R plants metabolized tribenuron-methyl significantly faster than did the susceptible (S) plants at 3, 5 and 7 day after treatment (DAT) of tribenuron-methyl. The malathion significantly reduced the tribenuron-methyl metabolism both in S and R plants. The tribenuron-methyl metabolism in S and R plants, which were firstly treated by malathion, displayed no significant difference at 1, 3 and 5 DAT. In addition, the completely new P450 gene CYP96A146 constitutively overexpressed in R plants, and the expression level of CYP96A146 in R plants was about 512-fold higher than in S plants comparing to S plants. The CYP96A146 expression in R plants was significantly induced by tribenuron-methyl at 1, 3, 5 and 7 DAT (1.9 to 2.9-fold). While, tribenuron-methyl induced CYP96A146 expression in S plants only at 5 DAT (16-fold). As P450 inhibitor, malathion can significantly weaken or reverse tribenuron-methyl-induction of CYP96A146 expression in S and R plants. CYP96A146 expression in R plants reduced about 30-, 2.6-, 1.4- and 1.5-fold at 1, 3, 5 and 7 DAT, respectively. By contrast, CYP96A146 expression in S plants decreased only at 5 DAT (4-fold). These results indicated the CYP96A146 conferred D. sophia metabolic resistance to tribenuron-methyl.

Metabolic resistance to tribenuron-methyl in Descurainia sophia L. conferred by cytochrome P450 enzyme (CYP96A146)

256th National Meeting (2018)

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