Characterization of two constitutive promoters RPS28 and EIF1 for studying soybean growth, development, and symbiotic nodule development

Native promoters that can drive high and stable transgene expression are important tools for modifying plant traits. Although several such promoters have been reported in soybean (Glycine max), few of them function at multiple growth and development stages and during nodule development. Here, we report that the promoters of 40S RIBOSOMAL PROTEIN SMALL SUBUNIT S28 (RPS28) and EUKARYOTIC TRANSLATION INITIATION FACTOR 1 (EIF1) are ideal for high expression of transgene. Through bioinformatic analysis, we determined that RPS28 and EIF1 were highly expressed during soybean growth and development, nodule development, and various biotic and abiotic stresses. Fusion of both RPS28 and EIF1 promoters, with or without their first intron, with the reporter gene β-GLUCURONIDASE (uidA) in transgenic soybean, resulted in high GUS activity in seedlings, seeds, and nodules. Fluorimetric GUS assays showed that the RPS28 promoter and the EIF1 promoter yielded high expression, comparable to the soybean Ubiquitin (GmUbi) promoter. RPS28 and EIF1 promoters were also highly expressed in Arabidopsis thaliana and Nicotiana benthamiana. Our results indicate the potential of RPS28 and EIF1 promoters to facilitate future genetic engineering and breeding to improve the quality and yield of soybean, as well as in a wide variety of other plant species.