Submitted to: Tropical Crop Biotechnology Conference 2006
Publication Type: Abstract Only
Publication Acceptance Date: 7/10/2006
Publication Date: 8/16/2006
Citation: Wang, M., Borth, W., Mangwende, T., Mirkov, E.T., Hu, J., Moore, P.H., Albert, H.H. 2006. Scylv p0: function and potential use to control transgene silencing in sugarcane. Tropical Crop Biotechnology Conference 2006. Cairns, Australia. pg.23. Interpretive Summary: None
Technical Abstract: Previously, we tested the feasibility of using sugarcane for the production of high-value proteins. Expression of a human cytokine, GM-CSF, in sugarcane resulted in the accumulation, under lab and field conditions, of recombinant protein that demonstrated essentially 100% native activity in a human cell culture proliferation assay. The highest producing sugarcane lines accumulated the recombinant protein at only 0.03% of total soluble protein (Wang et al. 2005). Production at that level would not be economical, even for a high-value protein like GM-CSF. Posttranscriptional gene silencing (PTGS) is one major barrier to achieving higher levels of recombinant protein production. The P0 proteins of three dicot infecting poleroviruses have been previously shown to suppress PTGS. To advance our understanding of PTGS in sugarcane, we are studying the P0 protein of Sugarcane Yellow Leaf Virus (SCYLV). We have demonstrated that SCYLV P0 also acts to suppress PTGS. In agrobacterium leaf infiltration experiments on Nicotiana benthamiana, SCYLV P0 suppresses local PTGS. Additionally, in most experiments, SCYLV P0 produces cell death in the infiltrated zone within approx. 3 days; when this occurs, systemic PTGS does not occur. For the three dicot infecting poleroviruses, P0 interacts with an ubiquitin ligase complex through an F-box protein-protein interaction domain. This led to the proposal that P0 acts by targeting a host protein essential for PTGS to proteosome degradation (Pazhouhandeh et al. 2006). P0 is proposed to interact with the host target protein through a second protein-protein interaction domain, however this has not been experimentally demonstrated and the host target protein has not been identified. SCYLV P0 contains the conserved F-box domain, and deletions that remove part or all of the proposed second protein-protein interaction domain diminish suppressor activity. Experiments are ongoing to further characterize this critical domain, to identify the target host protein, and to characterize transgenic sugarcane lines which constitutively express P0 and other viral suppressors of PTGS. Our goal in this aspect of the research will be to determine the feasibility of using viral suppressors of PTGS to control transgene silencing in sugarcane.