Dichlormid protect wheat from fomesafen residual injury by increasing PPO expression and the photosynthesis characterize

Fomesafen is a herbicide with long persistence in soil, causing damage to succeeding crops. Dichlormid is a widely used safener protecting maize from chloroacetanilide and thiocarbamate injury. We found that dichlormid treatment could restore the growth of wheat seedlings exposed to fomesafen stress. To explore its molecular mechanism, RNA-Seq was conducted to analysis transcript profiles between fomesafen and fomesafen+dichlormid treated wheat seedlings. The gene expression level was determined by qRT-PCR. Results showed that the up-regulated genes by dichlormid treatment were significantly enriched in pathways related to photosynthesis. The expression level of glutamyl-tRNA reductase (GTR), protoporphyrinogen IX oxidase (PPO, target of fomesafen), and magnesium chelatase (MAG) involved in chlorophyll biosynthesis was significantly up-regulated by dichlormid. And the expression level of genes in chlorophyll binding, energy biosynthesis, gibberellin biosynthesis and salicylic acid signal pathway was also validated to be significantly up-regulated by dichlormid. The detoxification enzyme activity of cytochrome P450 or glutathione S-transferase (GSTs), and their gene expression level was found to show no significant difference between fomesafen and fomesafen+dichlormid treatment. The antioxidant enzyme activity of peroxidase, superoxide, and the content malondialdehyde content was decreased by dichlormid, while the reduced glutathione content was increased by dichlormid significantly. The metabolism of fomesafen was further validated to be not influenced by dichlormid. These results suggested that dichlormid acted by increasing the expression of fomesafen target and photosynthesis related genes to alleviate fomesafen injury to wheat, but not accelerating fomesafen metabolism.