The Army Within the Plant: Identifying Tomato Genes Involved in Mi-1-Mediated Defense

In plants, resistance (R) gene-mediated defense confers resistance to a specific pest or pathogen following recognition of their avirulence (Avr) effectors. R-Avr mediated resistance is often conferred by a hypersensitive response that results in localized cell death at the infection site which starves the pathogen or pest. Mi-1 is a tomato R gene that confers resistance to rootknot nematodes, potato aphids and whiteflies. The signaling pathways involved during Mi-1mediated resistance are not fully understood. We have developed a high-throughput assay based on virusinduced gene silencing (VIGS) to identify genes essential for Mi-1 -mediated resistance. VIGS is a plant defense mechanism, where viral double-stranded RNA (dsRNA) is recognized by plant defense machinery and degraded into small-interfering RNA (siRNA). If a virus vector carries a plant gene, it also produces dsRNA and siRNA for that gene, leading to degradation of the endogenous RNA transcripts of that gene. This disables the function of that gene and we can determine if it has a role in Mi-1-mediated defenses by inducing HR on silenced leaves. We have used the Tobacco rattle virus (TRV) combined with a plant cDNA library, derived from pathogen induced tissue, to silence genes in Nicotiana benthamiana followed by infiltration with a spontaneous HR inducing variant of the Mi-1 gene . We observed attenuated HR in several silenced plants, indicating that the silenced genes play a role in the Mi-1-mediated HR. Winged Goddesses: Liminality and Gender in the Ancient World