Native polyubiquitin promoter of rice provides increased constitutive expression in stable transgenic rice plants

The rice Ubiquitin1 (Ubi1) promoter was tested to evaluate its capacity to express the heterologous gusA gene encoding β-glucuronidase in transgenic rice tissue relative to the commonly used Ubi1 corn promoter and the rice gibberellic acid insensitive (GAI) gene promoter element. Experimental results showed increased expression of gusA gene in rice tissue when driven by the native Ubi1 promoter when compared to the use of corn Ubi1 promoter. Results further indicated that the cis-regulatory elements present in the native promoter element might have been responsible for high expression. However, the gusA gene expression level when driven by the rice GAI promoter was notably lower than both Ubi1 promoters. The present study, thus, for the first time helped to demonstrate that the native Ubi1 promoter is a promising genetic element in transgenic approaches for constitutive expression of any gene in rice tissue.