TRANS REPLICATION AND HIGH COPY NUMBERS OF WHEAT DWARF VIRUS VECTORS IN MAIZE CELLS

The replication of shuttle vectors derived from Wheat Dwarf Virus, a monopartite geminivirus, was studied in cultured maize endosperm cells, and in the Black Mexican Sweet (BMS) maize cell line. Using in vivo labeling and DNA methylation analysis, we showed that replication was initiated within 24 hrs after transfection, and did not require cell division in both cell lines. Copy numbers of 30,000 ds DNA molecules per cell were observed in endosperm cells after three days. The replication protein was shown to act in trans, since the wild type gene of the shuttle vector enabled replication-deficient vectors carrying mutated genes to replicate. These properties suggest that WDV may have similar applications in plants as SV40 in mammalian cells.