|Navarre, Duroy - Roy|
Submitted to: Plant Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/27/2005
Publication Date: 5/1/2005
Citation: Hu, G., Dehart, A.K., Li, Y., Ustach, C., Handley, V., Navarre, R., Hwang, C.F., Aegerter, B.J., Williamson, V., Baker, B.J. 2005. EDS1 in tomato is required for resistance mediated by TIR-class R genes and the receptor-like R gene Ve. Plant Journal. 42(3):376-91. Interpretive Summary: In tobacco, tomato and other Solanaceae species, the N gene confers resistance to tobacco mosaic virus (TMV) and leads to induction of standard defense and resistance responses. Towards characterizing the N-TMV signaling pathway and its components, we identified a tomato mutant, sun1-1, that is defective in the N-TMV signal and determined that the sun1-1 mutation affects a tomato homolog of Arabidopsis EDS1. Tomato EDS1 lies upsteam of salicylic acid and is required for resistance mediated by TIR class resistance genes and the receptor-like resistance gene Ve. Relative to wild type susceptible plants, sun1-1 plants show enhanced susceptibility to TMV, providing evidence that the intersection of general and resistance gene-mediated pathways is conserved a Solanaceous species.
Technical Abstract: In tobacco and other Solanaceae species, the tobacco N gene confers resistance to tobacco mosaic virus (TMV), and leads to induction of standard defense and resistance responses. Here, we report the use of N-transgenic tomato to identify a fast-neutron mutant, sun1-1 (suppressor of N), that is defective in N-mediated resistance. Induction of salicylic acid (SA) and expression of pathogenesis-related (PR) genes, each signatures of systemic acquired resistance, are both dramatically suppressed in sun1-1 plants after TMV treatment compared to wild-type plants. Application of exogenous SA restores PR gene expression, indicating that SUN1 acts upstream of SA. Upon challenge with additional pathogens, we found that the sun1-1 mutation impairs resistance mediated by certain resistance (R) genes, (Bs4, I, and Ve), but not others (Mi-1). In addition, sun1-1 plants exhibit enhanced susceptibility to TMV, as well as to virulent pathogens. sun1-1 has been identified as an EDS1 homolog present on chromosome 6 of tomato. The discovery of enhanced susceptibility in the sun1-1 (Le_eds1-1) mutant plant, which contrasts to reports in Nicotiana benthamiana using virus-induced gene silencing, provides evidence that the intersection of R gene-mediated pathways with general resistance pathways is conserved in a Solanaceous species. In tomato, EDS1 is important for mediating resistance to a broad range of pathogens (viral, bacterial, and fungal pathogens), yet shows specificity in the class of R genes that it affects (TIR-NBS-LRR as opposed to CC-NBS-LRR). In addition, a requirement for EDS1 for Ve-mediated resistance in tomato exposes that the receptor-like R gene class may also require EDS1.