Characterization of the root-predominant gene promoter HPX1 in transgenic rice plants

Gene promoter(s) specialized in root tissues is an important component for crop biotechnology. In our current study, we report results of promoter analysis of the HPX1, a gene expressed predominantly in roots. The HPX1 promoter regions were predicted, linked to the gfp reporter gene, and transformed into rice. Promoter activities were analyzed in various organs and tissues of six independent transgenic HPX1:gfp plants using the fluorescent microscopy and q-RT-PCR methods. GFP fluorescence levels were high in root elongation regions but not in root apex and cap of the HPX1:gfp plants. Very low levels of GFP fluorescence were observed in anthers and leaves. Levels of promoter activities were 16- to 190-fold higher in roots than in leaves of the HPX1:gfp plants. The HPX1 promoter directs high levels of gene expression in root tissues producing GFP levels up to 0.39 % of the total soluble protein. Thus, the HPX1 promoter is predominantly active in the root elongation region during the vegetative stage of growth.