Characterization of soybean mosaic virus coat protein-mediated resistance in transgenic soybeans
Soybean plants transformed with the coat protein (CP) gene from soybean mosaic virus, strain N, were obtained by using Agribacterium tumefaciens mediated transformation. Polymerase chain reaction and Southern blot analyses were used to detect the transgene. Four insertion events were detected in T₀ plants by Southern blot analyses. Self-pollination of plants yielded four homozygous transgenic lines in the T₃ generation; they are transgenic lines 7b-11 with 5kb and 3kb insertion events, 3-24 with 7kb and 3.5kb insertion events, 3-3 with 7kb insertion event, 6-13 with 3.5kb insertion event. Northern blot analyses demonstrated the CP gene transcriptions in all the four transgenic lines while western blot analyses indicated expression of SMV coat protein in three transgenic lines. After inoculation with purified SMV, strain N, all four lines showed partial or complete resistance to the virus. Transgenic lines 7b-11 and 3-24 both have two insertion events, line 3-24 expressed high level of coat protein, whereas there is no detectable coat protein in line 7b-11. Despite this, both lines were highly resistant to virus. This result indicated the potential of both RNA and protein mediated resistance in transgenic plants.