Interactions between TMV and the tobacco N gene

(Les Erickson, University of California, Berkeley)
Plants use both preformed and inducible defense strategies to battle rogue microbes and insects. Gene-for-gene resistance is an inducible defense where pathogen recognition results from the specific interaction between a plant resistance gene and a pathogen gene. The presence of both of these genes induces a battery of defense responses that function to halt pathogen replication and spread. Our work focuses on the gene-for-gene interaction between tobacco mosaic virus (TMV) and plants containing the disease-resistance gene N. TMV infection of N-containing tobacco and tomato plants induces rapid defense responses, including cell death at the infection site, that limit viral replication, spread and disease. Specifically, my work addresses two fundamental questions concerning this interaction: 1) How does TMV infection trigger the host defense responses? 2) What is the role of the N gene product in TMV recognition and defense?

Previous work from Roger Beachys group showed that the TMV replicase proteins are involved in triggering the N gene-mediated defense responses. We have confirmed and extended this finding by showing that transient, non-viral expression of a TMV replicase gene fragment containing the putative helicase domain is sufficient to elicit N-mediated cell death (Abbink et al., 1998, MPMI 11:12, 1242-1246; Erickson et al., 1999, Plant J. 18:1, 67-76.). This discovery was further verified using transgenic plants, where tobacco seedlings expressing this TMV replicase fragment (termed p50) exhibited N gene-dependent cell death throughout the plant, killing the seedlings within two weeks after germination. Like the defense responses elicited by TMV infection, p50 expression induces a temperature-sensitive cell death response.

  • Abbink et al., 1998, MPMI 11:12, 1242-1246; Erickson et al., 1999, Plant J. 18:1, 67-76.