Analysis of virus-host interaction in multiplication of tobacco mosaic virus

点击翻译按钮获取中文摘要

Resistance-breaking strains named Lta1 and Ltb1 can overcome the resistance conferred by the Tm-1 and Tm-2 genes in tomato, respectively. To understand the resistance mechanisms and to get hints for normal process of multiplication of tobacco mosaic virus (TMV), mutations of Lta1 and Ltb1 responsible for overcoming the resistance were determined.From the nucleotide sequence comparison and subsequent reverse- genetic analysis, It was found that two base substitutions in the 130k/180k protein genes resulting in amino acid changes from Gln(979) to Glu and from His(984) to Tyr are important for the ability to overcome the Tm-1 resistance. Further analysis of other resistance-breaking strains and pseudorevertants suggested that an electrostatic interaction is involved in the resistance mechanism. Analysis in protoplasts supported that the resistance works in the course of replication. This is consistent with the involvement of the 130k and 180k proteins in replication.In the case of Ltb1, it was found that two base substitutions in the 30k protein gene resulting in amino acid changes from Cys(868) to Phe and from Glu(133) to Lys are involved in the property to overcome the Tm-2 resistance. Since the 30k protein is known to be involved in cell-to-cell movement, and since the mutations occur in well-conserved regions in the 30k protein, the Tm-2 gene would seem to block the normal cell-to-cell movement.Analysis using in vitro generated mutants revealed that the coat protein gene encodes the determinant for induction of the hypersensitive response in plants with the N' gene. It is not necessary to be assembled into virus particles.