| The genome of the Rice dwarf virus (RDV) comprised of 12 dsRNAs, encoding 7 structural and 5 nonstructural proteins, which interact with each other to form the vivion of this virus.Rice cell suspension culture system was established in this study. RDV was inoculated to the suspension cultured cells (SCC) by polyethylene glycol (PEG)-mediated system. Through sequential sampling, the replication dynamics of RDV within SCC and the expression mode of P8 and P9 proteins were detected employing enzyme-linked immunosorbnent assay (ELISA) and Western blot. It was found that RDV began to replicate on entering into SCC, reached its climax at 16 h after inoculation, and then gradually decreased, dropping to the lowest level at 50 h, but turn to increase at 68 h; However, P8 and P9 proteins started to express at 4 h and 8 h after inoculation, respectively, both peaked at 24 h or so and then gradually fell down.DNA probes of S8 and S9 labeled with digoxigenin (DIG) were prepared to investigate the transcriptional process of these two genes in SCC by Northern spot blotting. Both genes were found to initiate transcription at 4 h while their peak transcriptional times were different from each other, being at 12 h for S8 and 20 h for S9. This conclusion was further confirmed by Real time-PCR, which revealed the maximum of S8-mRNA transcript appeared at 24 h after treatment.Furthermore, changes of defense enzymes, i.e. peroxidase (POD),phenylanine (PAL) and polyphenoloxidase (PPO), indole acetic acid (IAA) and gibberellin (GA) for SCC was also determined in this study. It was showed that activity of all the three enzymes tested increased at different levels with the infection of RDV, peaking at 16 h, which is in accordance with the time of maximum replication of RDV was reached. However, the change profile of IAA was contrary, decreasing continually with the inoculation of RDV. For GA, the trend was opposite to that ofIAA.
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