Figure 3.

Extreme resistance induces expression of the PATHOGENESIS‐RELATED‐1 (PR‐1) gene. Leaves of Rx transgenic tobacco were either mock‐inoculated (M) or infected with potato virus X (PVX) (P). RNA was extracted from 1° inoculated leaves at 0 (M0 and P0) and 1 (M1 and P1) day post‐infection (dpi), and from systemic leaves at 0 (M0 and P0) and 5 (M5 and P5) dpi. RNA was subsequently used for reverse transcription followed by polymerase chain reaction (PCR) using primers targeting the tobacco acidic PR‐1 gene. The constitutively expressed translation elongation factor 1α gene (EF1α) was used as a control. Two independent experiments yielded similar results.