Poster: Plant-pathogen interactions

Abs # 512: 126-kDa protein is the structural determinant of the putative Tobacco Mosaic Virus replication complex

Presenter:	Liu, Jianzhong , jzliu@noble.org
Authors	Liu, Jianzhong  (A)   Nelson, Richard S. (A)
Affiliations:	(A): The Samuel Roberts Noble Foundation

Tobacco Mosaic Virus (TMV) is a single-stranded, plus-sense RNA virus that encodes at least four proteins: the 126/183 kDa proteins, 30 kDa movement protein, and 17.5 kDa capsid protein. The TMV 126-kDa protein contains methytransferase-like and helicase-like domains, while its read-through 183 kDa protein contains an additional polymerase domain. The126/183 kDa proteins are suggested to function as a heterodimer during TMV replication. The TMV 126-kDa protein is in ~10-fold excess to the 183-kDa protein in virus-infected cells, suggesting that the 126-kDa protein has functions additional to 126/183-kDa heterodimer formation for replication. The putative TMV replication complex is associated with the endoplasmic reticulum (ER) and contains the 126/183 kDa proteins, MP, and viral RNA. However, the viral factor(s) responsible for the formation of the replication complex is not fully understood for TMV. Here, we show that 126-kDa protein is ER-associated and formed cytoplasmic inclusion bodies in the absence of other viral components. Using mutant and parental 126 kDa protein genes expressed behind a 35S promoter and viruses expressing the corresponding 126 kDa protein genes, we determined that the size of the cytoplasmic inclusion bodies formed by 126 kDa proteins alone was positively correlated with the size of the putative replication complexes formed by the viruses. Also, an agent that disrupted the formation of 126 kDa inclusion bodies disrupted formation of the putative replication complexes. Taken together, our results suggest that 126-kDa protein, like the 1a in Brome Mosaic Virus, is the structural determinant of TMV replication complexes.