Distinct replication and gene expression strategies of the Rice Stripe virus in vector insects and host plants.

Persistent propagative plant viruses are usually transmitted between a vector insect and a host plant. To adapt to the two different organisms, viruses may show distinct genomic replication or gene expression patterns. To verify this hypothesis, we applied an aboslute real-time quantitative PCR method to measure and compare the replication levels of four genomic RNA segments and the expression levels of seven genes of rice stripe virus (RSV) according to the infection time in the small brown planthopper and rice plant, respectively. In the vector insect, RNA3 began replicating later than the other segments, and RNA2 remained nearly constant during the infection process. RNA1 was the dominant segment, and a difference of over 300-fold appeared among the four segments. In rice plants, the size of the four segments increased with infection time, but decreased to a low level in the late infection period. The ratios of the four segments varied by no more than 15-fold. In planthoppers, three expression patterns were observed for the seven viral genes during viral infection, while in rice plants, the expression patterns of the seven viral genes were similar. These results reflect distinct genomic replication and gene expression patterns in a persistent propagative plant virus in adapting to vector insects and host plants.