Molecular cloning and structural analysis of a novel Rac gene osRACB in rice (Oryza sativa L.)

As the sole ubiquitous signal GTP-binding protein in plants, Rac gene plays an important role in plant growth and development. Using another Rac gene osRACD as probe, we obtained a novel Rac gene osRACB from rice by screening the cDNA library of Nongken 58NLD young ears at formation stage of pistil and stamen under low stringent hybridization condition. The osRACB transcription unit was 2930 bp in length, composed of seven exons and six introns. In addition, the osRACB promoter was isolated by screening rice genomic DNA library. Southern blotting analysis revealed that osRACB was a low abundance gene in the nuclear genome. RT-PCR results suggested that osRACB was expressed in roots, stems and leaves, but the expression level in stems was much higher than that in other organs. Based on the human Rac1 model, we predicted the three-dimensional structure of osRACB by the Homology and Discover modules of Insight II.