Therefore, the appearance of necrotic symptoms upon inoculation of those two mutants may relate to the existence in plant cells of a R protein specifically detecting the "open" conformation of the GPP loop, whose sensing of the P866G/P867G mutant would be strong enough to induce HR and restrict the infection to the viral entry point, whereas part-time or weaker interactions with G865A would induce a delayed systemic necrosis. This evidence concerns the gene TCN1 and infection.