Truncated Ubiquitin 5′ Regulatory Region from Erianthus arundinaceus Drives Enhanced Transgene Expression in Heterologous Systems

Characterization of novel plant gene promoters underpins the development of transgenic crop plants. Here, we report a novel 5′ regulatory sequence (Eriubi D7) of the ubiquitin gene from Erianthus arundinaceus , a wild relative of sugarcane resistant to many biotic and abiotic stresses. A 3.2-kb regulatory sequence of ubiquitin gene was isolated through random amplification of genomic ends technique and characterized in rice, tobacco, and sugarcane. In silico analysis revealed that the regulatory sequence contained a promoter region of 1600 bp upstream to the transcription start site. Between the promoter and the coding region, two putative introns of 584 and 583 bp and two putative non-coding exons of 459 and 37 bp were spaced alternatively. To identify the active domains required for gene regulation, 12 truncations/recombinants were made in the regulatory sequence and characterized in heterologous systems. Transformation studies with the recombinant constructs revealed that Eriubi D7, a truncated fragment containing 830 bp promoter and the intron I, conferred enhanced GUS reporter gene expression in both monocots and dicots compared to other routinely used promoters such as maize ubi1 and Cauliflower Mosaic Virus 35S. Further analysis confirms that this regulatory sequence is quite distinct from the other reported ubiquitin promoters and was also found to enhance expression of the reporter gene upon wounding. This is the first report on the isolation and characterization of a promoter from a wild sugarcane germplasm and is expected to be useful for development of transgenic crop plants.