Molecular Characterization Of A Rice RING Finger Protein Gene OsBIRF1

Plants have evolved a series of complicated defense mechanisms against pathogen attack during their long-term process of co-evolvement. In addition to the race-cultivar specific disease resistance controlled by the resistance gene (R gene), plants have also evolved an adaptive inducible resistance mechanism in responding to pathogen invasion. In previous studies, two hundreds of differentially expressed cDNA clones associated with rice (Oryza sativa L.) disease resistance response were isolated and identified through suppression subtractive hybridization. Of these rice cDNA clones, clone BIHN-w1 showed a high level of similarity to RING finger proteins in plants. In order to elucidate the biological function of the putative RING finger protein gene, we cloned and identified full-length cDNA of the gene and designated as OsBIRFl (Oryza sativa L.BTH-induced RING finger protein 1). The full-length cDNA of the OsBIRF1 is 1837 bp with a predicted 1191bp open reading frame (ORF), which predicts to encode a 396 amino acid protein containing all conserved domains of the RING finger protein. OsBIRFl gene is located on chromosome 2 of the rice genome and consists of a single exon without intron.To elucidate the biochemical function of the OsBIRFl protein, recombinant OsBIRFl protein was purified from E. coli expressing the OsBIRFl coding region in a protein expression vector pRSET-A. In addition, to better understand the function of OsBIRFl in disease resistance response, we performed a functional analysis of OsBIRFl in transgenic tobacco plants. The OsBIRFl coding region was cloned into a plant transformation binary vector CHF3pp2p212 under control of the CaMV 35S promoter. A total of 9 kanamycin-resistant independent transgenic tobacco lines were obtained through the Agrobacterium-mediated leaf disc transformation and confirmed by PCR. Compared to wild type plants, the transgenic lines overexpressing OsBIRFl showed some morphological abnormalities in the bop buds, roots and reduced fertility, suggesting a role for OsBIRFl in plant development process.