Relationship between transcript production and virus resistance in transgenic tobacco expressing the potato leafroll virus coat protein gene.

The coat protein (CP) gene of potato leafroll luteovims (PLRV) was inserted into tobacco (Nicotiana tabacum) using disarmed Agrobacterium tumefaciens (LBA4404) containing a binary expression vector. PLRV CP gene transcript was detected in transgenic plants but its abundance differed between transformed lines. CP was not detected in virus-free transgenic plants. The segregation of kanamycin resistance in S1 seedling progenies (obtained by selfing transformed plants) indicated that multiple (up to five) integration events involving vector T-DNA had occurred in most transformants. However, the amount of detectable CP transcript was not related to the neomycin phosphotransferase II gene copy number. Multiplication of PLRV in mature transgenic plants was diminished by up to 6-fold; the greatest diminution was in those transformed lines in which most CP gene transcript was detected. However, S1 progeny seedlings of transgenic plants were no more resistant to infection, following inoculation with viruliferous aphids, than seedlings of non-transformed control plants.