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Title: CAPSID PROTEIN GENE AND THE TYPE OF HOST PLANT DIFFERENTIALLY MODULATE CELL-TO-CELL MOVEMENT OF COWPEA CHLOROTIC MOTTLE VIRUS

Author
item RAO, A - UNIVERSITY OF CALIFORNIA
item Cooper, Bret

Submitted to: Virus Genes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2006
Publication Date: 5/25/2006
Citation: Rao, A., Cooper, B. 2006. Capsid protein gene and the type of host plant differentially modulate cell-to-cell movement of cowpea chlorotic mottle virus. Virus Genes. 32:219-227.

Interpretive Summary: Soybean is one of America’s most important crops and a better understanding of the form and function of soybean genes could be of great help in combating soybean diseases. One potential tool for studying genes in soybean is cowpea chlorotic mottle virus (CCMV). Genes can be inserted into the CCMV using gentic engineering. Then the virus can infect soybean plants and spread the inserted gene as the virus spreads through the plants. However, the insertion of new genes into the virus can alter its rate of spread throughout the plant. Thus, a better understanding of how the virus spreads is needed before this virus can be used as a tool. In this study, a test gene, green fluorescent protein (GFP), was inserted into the virus so that the spread of the virus could be viewed as spread of the green color. CCMV with GFP moved slower in some types of plants. The results suggest that it may be possible to replace CCMV with new genes and test the effects of the new genes in soybean, but that rate of spread, which will influence the number of plant cells that eventually express the new gene, will be slowed. These data are most likely to influence scientists at universities, government agencies and companies who investigate and design virus for expressing genes and proteins in plants.

Technical Abstract: A study was undertaken to measure the rate of coat protein (CP) independent cell-to-cell movement of cowpea chlorotic mottle bromovirus (CCMV) in three different host plants. A CCMV RNA3 variant in which the CP gene was substituted with enhanced green fluorescent protein (C3/'CP-EGFP) was coinoculated to three different host plants with transcripts of wild type RNAs 1 and 2. Comparative analysis of cell-to-cell movement monitored by the EGFP expression at various days post inoculation revealed that the rate of spread varied with the type of host species inoculated: fastest movement was observed in Nicotiana benthamiana while the rate spread was significantly slower in the natural host cowpea. When CP was expressed as EGFP fusion (C3/CP:EGFP) the rate of spread in N. benthamiana and C. quinoa was slower than that was observed in the absence of CP and remained subliminal in cowpea. Analysis of infection foci by confocal laser scanning microscope revealed that localization of CP:EGFP fusion was distinct in N. benthamiana and C.quinoa and accumulated as fluorescent inclusions at the cell periphery. Additional experiments involving coinoculation of either C3/'CP-EGFP or C3/CP:EGFP with heterologous brome mosaic bromovirus (BMV) genomic RNAs 1 and 2 revealed that, in addition to movement protein and CP, viral replicase also influences cell-to-cell spread. The significance of these results in relation to the mechanism of bromovirus movement is discussed.