Transgene Silencing in Wheat Transformed with the WSMV-CP Gene

Wheat (Triticum aestivum) was co-transformed with the bar gene and Wheat Streak Mosaic Virus Coat Protein gene (WSMV-CP) by the biolistic method. Transgenic wheat carrying the WSMV-CP showed non-uniform segregation patterns due to transgene loss or silencing. Loss of transgene expression was observed at the T1, T2 or T3 generations. Among these silenced lines, transgenic line 566B was chosen for detailed studies. Results indicated that all 566B T1 plants containing the WSMV-CP expressed WSMV coat protein and all showed strong resistance to WSMV. While the WSMV-CP was carried through to the T2 and T3 generations, all transgenic plants in these generations showed transgene silencing. Expression of WSMV-CP could be restored, at least temporarily, in most of these silenced plants by treatment with 5-azacytidine (5-AzaC).