Development of transient expression system for gene functional analysis in Setaria viridis

An efficient transient expression system to enable functional gene analysis was developed in Setaria viridis, a new C4 model plant. A promoter deletion analysis of C4 phosphoenolpyruvate carboxylase (PEPC) was used to demonstrate the protoplast transient expression system mediated by polyethylene glycol (PEG). Protoplasts were isolated from young leaves of S. viridis. A series of promoter deletion fragments ranging in size from 243 to 859 bp were fused to firefly luciferase and co-transfected with Renilla luciferase. Luciferase levels were used to determine promoter activities based on the ratio of firefly/Renilla to normal cell number and transfection efficiency. Luciferase activities of the longer PEPC promoter constructs exhibited higher promoter activities. Results revealed potential uses of the protoplast transient expression system for promoter analysis in S. viridis.