Isolation and characterization of the EgWRI1 promoter from oil palm (Elaeis guineensis Jacq.) and its response to environmental stress and ethylene.

WRI1 is a plant-specific transcription factor that enhances the accumulation of oils through the upregulation of the expression of genes involved in glycolysis and fatty acid biosynthesis. In this study, the EgWRI1 promoter from oil palm was isolated and characterized in transgenic Arabidopsis. The sequence analysis results revealed that various putative plant regulatory elements are present in the EgWRI1 promoter region. The EgWRI1 promoter and beta-glucuronidase (GUS) reporter gene were transcriptionally fused and transformed into Arabidopsis thaliana. Histochemical analysis revealed that GUS staining was very strong in whole seedlings, especially the stems, leaves, and siliques. Moreover, GUS staining was strong in the silique coats but weak in the seeds. Furthermore, to detect whether EgWRI1 was induced by environmental stress, we detected the expression efficiency of the EgWRI1 promoter in transgenic Arabidopsis treated with low temperature, darkness, and exogenous ethylene. The results showed that the activity of the EgWRI1 promoter was induced by darkness but suppressed significantly when exposed to exogenous ethylene. When treated with low temperature, the activity of the EgWRI1 promoter was first reduced after 24 hours but recovered after 48 hours. Taken together, these results reveal the features of the EgWRI1 promoter from oil palm, which will be helpful for improving oil accumulation in oil palm via reasonable cultivation methods.