Development and Utilization of the DsRed2 Visual Reporter Gene System Driven by Soybean GmUbi Promoter

Screenable reporter genes are essential tools for plant genetic engineering and transgenic breeding. Red fluorescent protein represented by DsRed2 has distinct advantages including no requirement for exogenous substrates, non-destructive detection and low plant autofluorescence interference, collectively conferring strong potential for transgenic screening applications. The ubiquitin promoter is well established as a broadly active constitutive promoter; however, the capacity of the soybean-endogenous ubiquitin ( GmUbi ) promoter to drive DsRed2 expression as an effective visual reporter system has not been systematically characterized. In this study, we constructed two expression vectors carrying DsRed2 driven by the CaMV 35S promoter and GmUbi promoter respectively. Soybean hairy root transformation was first performed to evaluate promoter activity via fluorescence quantitative analysis. Fluorescence intensity in hairy roots driven by the GmUbi promoter was significantly higher than that driven by the 35S promoter, with mean fluorescence intensity (MFI) values of 79.85 and 35.55, respectively. The red fluorescence intensified progressively over time, reflecting continuous accumulation of DsRed2 protein. Subsequently, the GmUbi promoter-DsRed2 expression cassette was transformed into Arabidopsis thaliana and soybean. Obvious red phenotypes were visually observed in siliques, seeds and floral organs of transgenic Arabidopsis , as well as in flowers, leaves, pods and seed coats of transgenic soybean. The color difference caused by DsRed2 accumulation allowed direct discrimination between transgenic and non-transgenic materials by naked eyes throughout plant growth and seed germination stages. Taken together, these results demonstrate that the soybean GmUbi promoter drives robust transcriptional activity in both Arabidopsis and soybean. The GmUbi promoter-DsRed2 reporter system provides a simple, rapid, and non-destructive strategy for the visual screening of transgenic events, offering broad utility in plant genetic transformation and related biotechnological research.