Expression of Detoxification Proteins and Tissue-Specific Transcriptome Profiling in Etiolated Coleoptiles of Grain Sorghum Following Safener and Oxylipin Treatments.

Herbicide safeners, non-phytotoxic compounds, protect cereal crops from herbicide injuries by inducing genes involved in detoxification such as glutathione S-transferases and P450s. Although the pathway to promote the expression of detoxification genes is not clear yet, a previous study found that GST proteins that are involved in xenobiotic detoxification were highly expressed in the outermost cells of wheat (Triticum tauschii) seedling coleoptiles by safener treatment. A previous research of gene expression analysis in cell cultures of Arabidopsis showed that oxylipins (B₁-type phytoprostanes, PPB₁) triggered a massive detoxification and defense response which included GSTs and glycosyl transferases. These previous discoveries led to the hypotheses that safeners may utilize the pre-existing signaling pathway for detoxification and possibly an oxidized lipid-mediated singling pathway. In this project, we performed the immunolocalization studies to test the abundance and the pattern of GST expression in sorghum shoots in response to untreated and safener treated. In addition, we conducted the whole transcriptome profiles of the outermost cell layer of sorghum coleoptiles in two different genotypes, BTx623 and SC0087. The RNA-seq experiment allowed us to investigate the altered transcripts after safener and oxylipin (phytoprostane-A1) treatments during a time course. The greater accumulation of GST proteins was observed in safener treated tissues and the expression was distributed more in the outermost coleoptile cells of sorghum shoots. The transcriptome analysis of safener and PPA₁ –regulated transcripts in two sorghum genotypes identified several transcripts involved in stress responses, lipid transfer, and signaling pathways. This research will elucidate the unknown mechanisms of detoxification related to safener and signaling and stress-response genes in cereal crops.