Figure 3

Dose-dependent interference with PMMoV infection by bacterial crude preparations expressing PMMoV IR 54. (A) Northern blot analysis of total RNA extracted from inoculated leaves (lanes 3 to 7) of N. benthamiana at 7 dpi. Plants were inoculated with mixtures of PMMoV (5 μg/ml) plus either a series of dilutions (1/2 to 1/20) of the PMMoV IR 54 preparation, or the PPV HC dsRNA preparation diluted 1/2, as indicated. French Press preparations derived from bacteria expressing the empty vector (HT115) or PMMoV IR 54 used in the inoculum were run in lanes 1 and 2, respectively. RNA samples (1 μg) were fractionated by 1% agarose gel electrophoresis and the filter was hybridised with a DIG-labeled PMMoV 54-kDa RNA probe. Equal loading of RNA samples was assessed using a DIG-labeled RNA probe complementary to the 18S ribosomal RNA. The positions of PMMoV RNA and 18S RNA are indicated in the margin. (B) Response of N. benthamiana to a combination of PMMoV plus French Press preparations derived from either PMMoV IR 54 (left), PPV HC dsRNA (middle) or HT115 (right). Plants displaying disease symptoms (one-half-diluted, PPV HC dsRNA and HT115 preparations) or showing protection to virus infection (1/10-diluted PMMoV IR 54 preparation) were photographed at 30 dpi.